Matteo POSTACCHINI

Pubblicazioni

Matteo POSTACCHINI

 

82 pubblicazioni classificate nel seguente modo:

Nr. doc. Classificazioni
40 4 Contributo in Atti di Convegno (Proceeding)
36 1 Contributo su Rivista
5 2 Contributo in Volume
1 8 Tesi di dottorato
Anno
Risorse
2021
Human stability during floods: Experimental tests on a physical model simulating human body
SAFETY SCIENCE
Autore/i: Postacchini, M.; Bernardini, G.; D'Orazio, M.; Quagliarini, E.
Classificazione: 1 Contributo su Rivista
Abstract: Urban floods are becoming more and more intense and frequent allover the world. Extreme events are the main triggering factors of such floods, and merit attention for what concerns the urban planning and emergency strategies. Numerical models aimed at investigating the optimal paths for evacuees escaping a flooded urban environment may be used by local authorities to properly understand how to improve people safety and mitigate the flood risk. Implementation of empirical laws in such models to describe the people stability in flooded areas is thus crucial to understand the behavior of evacuees and rescuers during emergency conditions. Laboratory experiments have been undertaken using a physical model representing a human body at quasi-natural scale, towed by an electrical engine in the water at rest. This represents a novel laboratory approach which exploits a non-inertial reference frame in motion with the model. The experimental results, obtained using different combinations of water depth and flow speed, have led to empirical laws which outline the stability conditions occurring when either the model front or the model back faces the flow, these respectively corresponding to Backward Toppling Instability (BTI) and Forward Toppling Instability (FTI). Such laws have been found through comparison with reference literature works, using various statistical methods. The FTI condition has been seen to largely improve the human stability compared to BTI, in contrast to the results of previous literature works, which stated an overall similarity between the results of the two toppling conditions. To better understand the role of the water flow during the different tests, hydraulic forces and moments have been measured. It has been seen that dynamic and static effects are comparable during high-speed conditions, especially due to a relevant fluid-model interaction and an increase of the water-surface level, while dynamic effects are negligible during low-speed conditions. The results of the present contribution can represent an important step forward for the numerical models applied to the framework of urban and emergency planning.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287664 Collegamento a IRIS

2021
Coastal sensitivity/vulnerability characterization and adaptation strategies: A review
JOURNAL OF MARINE SCIENCE AND ENGINEERING
Autore/i: Anfuso, G.; Postacchini, M.; Di Luccio, D.; Benassai, G.
Classificazione: 1 Contributo su Rivista
Abstract: Coastal area constitutes a vulnerable environment and requires special attention to preserve ecosystems and human activities therein. To this aim, many studies have been devoted both in past and recent years to analyzing the main factors affecting coastal vulnerability and susceptibility. Among the most used approaches, the Coastal Vulnerability Index (CVI) accounts for all relevant variables that characterize the coastal environment dealing with: (i) forcing actions (waves, tidal range, sea-level rise, etc.), (ii) morphological characteristics (geomorphology, foreshore slope, dune features, etc.), (iii) socio-economic, ecological and cultural aspects (tourism activities, natural habitats, etc.). Each variable is evaluated at each portion of the investigated coast, and associated with a vulnerability level which usually ranges from 1 (very low vulnerability), to 5 (very high vulnerability). Following a susceptibility/vulnerability analysis of a coastal stretch, specific strategies must be chosen and implemented to favor coastal resilience and adaptation, spanning from hard solutions (e.g., groins, breakwaters, etc.) to soft solutions (e.g., beach and dune nourishment projects), to the relocation option and the establishment of accommodation strategies (e.g., emergency preparedness).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287539 Collegamento a IRIS

2021
Experimental investigation on micro-hydropower generation and real-world application
6th IAHR Europe Congress - Book of Abstract
Autore/i: Postacchini, M.; Darvini, G.; Soldini, L.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/289469 Collegamento a IRIS

2021
Assessing the flood risk to evacuees in outdoor built environments and relative risk reduction strategies
INTERNATIONAL JOURNAL OF DISASTER RISK REDUCTION
Autore/i: Bernardini, G.; Finizio, F.; Postacchini, M.; Quagliarini, E.
Classificazione: 1 Contributo su Rivista
Abstract: Climate-change induced disasters, like floods, are expected to increase in the future. In outdoor built environments, flood risk to evacuees depends on interactions between floodwater spreading, built environment features, flood-induced modifications, and individuals’ reaction in emergency phases. Disaster risk reduction strategies should mitigate the immediate flood impacts and improve the community resilience, while being easy-to-implement and effectively supporting evacuees during the initial phases of the emergency. Simulation-based methodologies could support safety planners in evaluating the effectiveness of such strategies, especially if basing on a micro-scale-oriented approach that represents emergency interactions between each individual and the surrounding outdoor built environment. This study adopts an existing micro-scale simulator (FlooPEDS) reproducing experimental-based flood evacuation behaviours. According to a behavioural design-based approach, simulation results focus on individual responses in the outdoor built environment through Key Performance Indicators (KPIs) aimed at providing evidence of critical interactions between evacuees, floodwaters and the outdoor built environment. A case study is selected by considering different flood scenarios to test such KPIs. Risk reduction solutions are then provided, and their effectiveness is checked by simulations. Results show the micro-scale and behavioural design-based approach capabilities in proposing multi-scenarios solutions (e.g.: architectural elements to support evacuees; emergency planning).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/291669 Collegamento a IRIS

2021
Wave-Forced Dynamics at Microtidal River Mouths
River Deltas - Recent Advances
Autore/i: Brocchini, Maurizio; Postacchini, Matteo; Melito, Lorenzo; Perugini, Eleonora; Manning, Andrew J.; Smith, Joseph P.; Calantoni, Joseph
Editore: IntechOpen
Classificazione: 2 Contributo in Volume
Abstract: Microtidal river mouths are dynamic environments that evolve as a consequence of many forcing actions. Under the hydrodynamic viewpoint, river currents, sea waves and tides strongly interact, and their interplay determines specific sediment transport and morphological patterns. Beyond literature evidence, information comes from field observations made at the Misa River study site, a microtidal river along the Adriatic Sea (Italy), object of a long-going monitoring. The river runs for 48 km in a watershed of 383 km2, providing a discharge of about 400 m3/s for return periods of 100 years. The overall hydrodynamics, sediment transport and morphological evolution at the estuary are analyzed with particular attention to specific issues like: the generation of vortical flows at the river mouth, the influence of various wave modes (infragravity to tidal) propagating upriver, the role of sediment flocculation, the generation and evolution of bed features (river-mouth bars and longitudinal nearshore bars). Numerical simulations are also used to clarify specific mechanisms of interest.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/291760 Collegamento a IRIS

2020
Hydropower Generation Through Pump as Turbine: Experimental Study and Potential Application to Small-Scale WDN
WATER
Autore/i: Postacchini, Matteo; Darvini, Giovanna; Finizio, Fiorenza; Pelagalli, Leonardo; Soldini, Luciano; Di Giuseppe, Elisa
Classificazione: 1 Contributo su Rivista
Abstract: Pump-As-Turbine (PAT) technology is a smart solution to produce energy in a sustainable way at small scale, e.g., through its exploitation in classical Water Distribution Networks (WDNs). PAT application may actually represent a suitable solution to obtain both pressure regulation and electrical energy production. This technology enables one to significantly reduce both design and maintenance costs if compared to traditional turbine applications. In this work, the potential hydropower generation was evaluated through laboratory tests focused on the characterization of a pump working in reverse mode, i.e., as a PAT. Both hydrodynamic (pressure and discharge) and mechanical (rotational speed and torque) conditions were varied during the tests, with the aim to identify the most efficient PAT configurations and provide useful hints for possible real-world applications. The experimental findings confirm the good performances of the PAT system, especially when rotational speed and water demand are, respectively, larger than 850 rpm and 8 L/s, thus leading to efficiencies greater than 50%. Such findings were applied to a small municipality, where daily distribution of pressure and discharge were recorded upstream of the local WDN, where a Pressure Reducing Valve (PRV) is installed. Under the hypothesis of PRV replacement with the tested PAT, three different scenarios were studied, based on the mean recorded water demand and each characterized by specific values of PAT rotational speed. The best performances were observed for the largest tested speeds (1050 and 1250 rpm), which lead to pressure drops smaller than those actually due to the PRV, thus guaranteeing the minimum pressure for users, but also to mechanical powers smaller than 100 W. When a larger mean water demand is assumed, much better performances are reached, especially for large speeds (1250 rpm) that lead to mechanical powers larger than 1 kW combined to head drops a bit larger than those observed using the PRV. A suitable design is thus fundamental for the real-world PAT application.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/275984 Collegamento a IRIS

2020
Upstream Propagating Long‐Wave Modes at a Microtidal River Mouth
e-proceedings of the 4 th EWaS International Conference Valuing the Water, Carbon, Ecological Footprints of Human Activities
Autore/i: Postacchini, Matteo; Melito, Lorenzo; Sheremet, Alex; Calantoni, Joseph; Darvini, Giovanna; Corvaro, Sara; Memmola, Francesco; Penna and Maurizio Brocchini, Pierluigi
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/290536 Collegamento a IRIS

2020
The effects of hydraulic jumps instability on a Natural river confluence: The case study of the Chiaravagna River (Italy)
WATER
Autore/i: De Leo, A.; Ruffini, A.; Postacchini, M.; Colombini, M.; Stocchino, A.
Classificazione: 1 Contributo su Rivista
Abstract: The occurrence and the effects of hydraulic jump instabilities on a natural river confluence in a small river basin in Liguria (Italy) is here investigated. Hydraulic jump instability has been extensively studied in controlled and simplified laboratory rectangular flumes. In the present study, a scaled physical model of the Chiaravagna River and Ruscarolo Creek confluence has been used, retaining the realistic geometry of the reaches. This reach has been subject to frequent floods in the last twenty years and the entire area of the confluence has been redesigned to decrease the flood risk. A series of experiments has been performed varying the discharge on the two reaches and the geometrical configurations. Free surface levels and two dimensional horizontal velocities have been measured in several positions along the physical model. The analysis of the water levels and velocities reveals that oscillations characterised by large amplitude and low frequency occur under particular hydraulic conditions. These oscillations have been found to be triggered by the hydraulic jump toe instability of the smallest reach of the confluence. Aiming at reducing the amplitude of the oscillations, which can be of the order of the flow depth, possible constructive solutions have been tested to control or damp the oscillations. Indeed, the insertion of a longitudinal dyke at the confluence has proven to be an effective solution to limit the amplitude of the transversal oscillations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/286126 Collegamento a IRIS

2020
Hydrodynamics at a microtidal inlet: Analysis of propagation of the main wave components
ESTUARINE, COASTAL AND SHELF SCIENCE
Autore/i: Melito, Lorenzo; Postacchini, Matteo; Sheremet, Alex; Calantoni, Joseph; Zitti, Gianluca; Darvini, Giovanna; Penna, Pierluigi; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: The evolution of different wave components as they propagate within a microtidal inlet during a storm occurring from 24–26 January 2014 is analyzed, in order to improve knowledge on how microtidal river mouths typical of the Adriatic Sea behave. For the first time, the ”low-pass filter” mechanism previously ascertained at several macrotidal oceanic inlets around the world has been observed in the field with remarkably specific hydrodynamic conditions, i.e. low tide excursion, permanent connection with the sea and generally milder wave climate than in the ocean. Sea/swell (SS) waves were strongly dissipated before entering the river mouth, through the combined action of wave breaking due to reducing depths and opposing river currents enhanced by rainfall. Infragravity (IG) waves propagated upstream and significant IG wave heights of up to 0.4 m, about 13% of the local water depth, have been observed 400 m upriver (about 10 times the local SS peak wavelength) during storm climax. The IG wave energy here represented over 4% of the maximum offshore storm energy. IG wave components travelled upriver at estimated velocities between 3.6 m/s and 5.5 m/s (comparable with speeds of nonlinear long waves) during intense storm stages up to 600 m into the river channel (about 15 times the local SS peak wavelength), and are enhanced by tide-induced increase in water depths. It is estimated that tide-induced excursion accounted for about 80% of the total mean water elevation at storm peak at about 400 m into the river. Finally, tidal oscillations are detected up to 1.5 km upstream (about 40 times the local SS peak wavelength). This study highlights the dominance of astronomical tide over both wave setup and storm surge in controlling the upriver propagation of IG waves, even in a microtidal environment.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273197 Collegamento a IRIS

2020
Sandbar dynamics in microtidal environments: Migration patterns in unprotected and bounded beaches
COASTAL ENGINEERING
Autore/i: Melito, Lorenzo; Parlagreco, Luca; Perugini, Eleonora; Postacchini, Matteo; Devoti, Saverio; Soldini, Luciano; Zitti, Gianluca; Liberti, Luca; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: Novel observations of bar features and migration patterns at three Italian sandy beaches in Senigallia (central Adriatic Sea) and Terracina (central Tyrrhenian Sea) are presented. While two of these beaches are unprotected, one is artificially embayed through the presence of a concrete jetty. Bar locations and motions are analysed with video imagery data sets from coastal monitoring stations. Wave climate from the Copernicus oceanographic model is used to correlate hydrodynamics and beach morphology. Clear net offshore migration (NOM) patterns are identified at all beaches, although exhibiting different response scales. At the low-slope beach of Senigallia (mean surf zone slope of 0.009) bars are more sensitive to seasonal changes in wave climate, with offshore shifts in winter and inactivity in summer. Mean annual migration rates of up to 0.26 m/day and 0.09 m/day are observed for outer and inner bars, respectively. No significant response to single storms is observed, except during a single NNE storm. No distinct erosive or accretive trend for the shoreline is evidenced. At the steep beach of Terracina (mean surf zone slope of 0.018), conversely, bars are strongly responsive to single storm events, with displacements of up to 25–50 m across a single storm. The mean inter-annual migration rate is 0.08 m/day for the single/outer bar, whereas a slight onshore trend (-0.02 m/day) for the newborn inner bar is established. The presence of an artificial jetty at the Misa river mouth in Senigallia, finally, leaves the bar system, typically oscillating around an equilibrium position, susceptible to larger seasonal oscillations and strong offshore migration due to two ESE storm events. Numerical simulations of nearshore circulation for two storms from different directions predict the birth of longshore currents, higher ratios of significant wave height to water depth, and stronger bottom orbital velocities over bars in case of the ESE storm, suggesting a greater tendency for offshore-directed sediment transport.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/283529 Collegamento a IRIS

2019
INFLUENCE OF STORM SEQUENCING AND BEACH RECOVERY ON SEDIMENT TRANSPORT AND BEACH RESILIENCE (RESIST)
Proceedings of the HYDRALAB+ Joint User Meeting
Autore/i: Eichentopf, Sonja; Baldock, Tom E.; Cáceres, Iván; Hurther, David; Karunarathna, Harshinie; Postacchini, Matteo; Ranieri, Nicola; van der Zanden, Joep; Alsina, José M.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Large-scale experiments on beach profile evolution and detailed sediment transport processes under varying wave conditions were performed within the HYDRALAB+ transnational access project ‘RESIST’. Five wave conditions were tested, of which two presented high energy wave conditions and three presented low energy wave conditions (including one very low energy condition that was run for a long duration (24 h)). These five wave conditions were combined into three sequences of alternating high-low energy conditions, with similar total power of each sequence. Each sequence departed from an initial 1/15 sloped profile. The experiments resulted in a large data set comprising measurements of high temporal-spatial resolution of the beach profile, water surface elevation, velocity field, sediment concentrations as well as the collection of sediment samples and observations of wave breaking and runup/rundown. The analysis of the beach profiles in the context of storm sequence forcing has highlighted the evolution of the beach towards an equilibrium state for each wave condition. The analysis of sediment transport and bed level changes under high energy, alternating swash events has provided new insights into sand transport processes, including the influence of small differences in waveswash interactions on transport rates, and the mobilisation of sediment in the swash.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/270376 Collegamento a IRIS

2019
Monitoring for Coastal Resilience: A Project for Five Italian Beaches
Proceedings of the 2018 IEEE International Workshop on Metrology for the Sea
Autore/i: MELITO, LORENZO; Luca, Parlagreco; PERUGINI, ELEONORA; POSTACCHINI, Matteo; ZITTI, GIANLUCA; BROCCHINI, Maurizio
Editore: IEEE
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: This paper presents the COPEMAP project, fruit of a research collaboration between the Università Politecnica delle Marche and the Istituto Superiore per la Protezione e la Ricerca Ambientale. The project focuses on developing a methodology for the assessment of beach resilience as a function of both natural forcing (e.g. incoming wave fields) and natural protection (e.g. underwater sand bars). This is accomplished through simplified analyses of available video-monitoring data.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263465 Collegamento a IRIS

2019
Research and Engineering for Resilient Infrastructures and Environment Protection
The First Outstanding 50 Years of “Università Politecnica delle Marche”
Autore/i: Bocci, Maurizio; Brocchini, Maurizio; Canestrari, Francesco; Cardone, Fabrizio; Corvaro, Sara; Darvini, Giovanna; Ferrotti, Gilda; Graziani, Andrea; Lorenzoni, Carlo; Mancinelli, Alessandro; Postacchini, Matteo; Soldini, Luciano; Virgili, Amedeo
Classificazione: 2 Contributo in Volume
Abstract: We discuss the contribution of the research groups that work at UNIVPM in the field of infrastructure engineering to the design of resilient hydraulic and transportation infrastructures and related solutions for the protection of the environment. After recalling the long history of research and engineering intervention of the groups of Hydraulics and Transportation Infrastructures of UNIVPM, we show how the activities of such groups are becoming of increasing importance in response to the growing request of innovative solutions for resilient infrastructures (e.g. coastal protection and maritime structures, road and airport pavements) and environment protection (e.g. coastal and river flood, air pollution, waste recycling and materials reuse). Such activities have been recently boosted by the resources made available to the two groups through the “Dipartimenti di Eccellenza” award, which largely focuses on the issue of engineering for resilient built and natural environments. A projection in the future of the activities of above is also proposed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273420 Collegamento a IRIS

2019
Sustainable Engineering for Resilient Built and Natural Environments
The First Outstanding 50 Years of “Università Politecnica delle Marche”
Autore/i: Alici, Antonello; Bocci, Maurizio; Bonvini, Paolo; Brocchini, Maurizio; Calamai, Alessandro; Canestrari, Francesco; Capozucca, Roberto; Carbonari, Alessandro; Carbonari, Sandro; Cardone, Fabrizio; Clementi, Francesco; Clini, Paolo; Cocchi, Giammichele; Corvaro, Sara; Darvini, Giovanna; Davì, Fabrizio; Dezi, Luigino; Di Giuseppe, Elisa; D’Orazio, Marco; Ferretti, Maddalena; Ferrotti, Gilda; Gara, Fabrizio; Giretti, Alberto; Graziani, Andrea; Lancioni, Giovanni; Lemma, Massimo; Lenci, Stefano; Lorenzoni, Carlo; Malinverni, Eva Savina; Mancinelli, Alessandro; Mariano, Fabio; Mentrasti, Lando; Mondaini, Gianluigi; Montecchiari, Piero; Munafò, Placido; Naticchia, Berardo; Postacchini, Matteo; Quagliarini, Enrico; Quattrini, Ramona; Ragni, Laura; Serpilli, Michele; Soldini, Luciano; Virgili, Amedeo; Zampini, Giovanni
Editore: Springer
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/272866 Collegamento a IRIS

2019
A model chain approach for coastal inundation: Application to the bay of Alghero
ESTUARINE, COASTAL AND SHELF SCIENCE
Autore/i: Postacchini, Matteo; Lalli, Francesco; Memmola, Francesco; Bruschi, Antonello; Bellafiore, Debora; Lisi, Iolanda; Zitti, Gianluca; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: Coastal inundation is an important threat for many nearshore regions worldwide, and has significantly increased in the last years also due to sea-level rise and augmented impact of extreme events, like sea storms. Many countries and regions have recently invested to overcome such problems, which commonly lead to structure damages, beach erosion and many other consequences. Numerical modeling is an important tool for coastal inundation prediction, being a valuable support for management issues to mitigate the inundation risk or suggest resilient solutions. The present work illustrates a novel approach, based on a numerical model chain that exploits a tide-surge-wave operational modeling system (Kassandra), a phase-averaged model (ROMS-SWAN) for the wave propagation towards the shore, and a phase-resolving solver (NSWE) for the prediction of runup and coastal inundation. Such a chain is applied to the bay of Alghero (Sardinia, Italy), where the results of the mentioned chain are compared to those obtained using, in place of the phase-averaged model, an analytical model for the wave propagation. Results confirm that both chain approaches provide comparable inundations, though the use of the analytical, more approximate (e.g., less accurate and reliable description of wave breaking dissipation), model suggests more severe conditions and larger flooded areas. Our contribution provides a methodological approach for an accurate and reliable estimate of coastal flooding.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263424 Collegamento a IRIS

2019
Flooding Pedestrians’ Evacuation in Historical Urban Scenario: A Tool for Risk Assessment Including Human Behaviors
RILEM Bookseries
Autore/i: Bernardini, Gabriele; Postacchini, Matteo; Quagliarini, Enrico; D’Orazio, Marco; Brocchini, Maurizio
Editore: Springer Netherlands
Classificazione: 2 Contributo in Volume
Abstract: In the future, safety in historical city centers will be significantly affected by climate change-related disasters, such as floods. Risk assessment in these scenarios requires the combination of a series of factors: possible events characterization; urban layout configuration, its influence on flooding spreading and induced environmental modification; human factor, especially during first emergency phases. Historic urban scenario features (e.g.: compact urban fabrics; position near floodplains; possible inefficient early warning systems) additionally increase individuals’ risks. According to a “behavioral design” approach, developing flood evacuation simulation tools would help safety designers in assessing population’s exposure and then in suggesting emergency strategies to help citizens during such hazardous phases. This paper proposes a flooding evacuation simulation tool, which jointly represents the individuals’ evacuation motion towards safe areas, and the floodwaters spreading in the urban scenario. In particular, the simulator is founded on previous literature results concerning emergency behaviors and motion quantities (e.g.: evacuation speed as function of floodwaters flow) and adopts an agent-based model architecture. A part of the historic city center of Senigallia, an Italian city that suffered a significant flood in 2014, is chosen as application case-study to show tool capabilities. Results outline risk levels for individuals, and evidence critical points (in the urban space and during the time) for man-floodwaters-environment interactions (e.g.: being swept away by floodwaters). By evaluating probable evacuees’ choices in different scenarios, the tool is proposed to check the effectiveness of solutions for reducing evacuation process risks (e.g.: emergency planning; architectural elements development; interventions for floodwaters collection also in urban scenarios).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263425 Collegamento a IRIS

2019
Long waves approaching the coast: Green’s law generalization
JOURNAL OF OCEAN ENGINEERING AND MARINE ENERGY
Autore/i: Lalli, Francesco; Postacchini, Matteo; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: The original Green’s relationship provides the amplitude of a long wave at a given water depth as a function of the amplitude in deeper waters, accounting for the wave shoaling, taken as a one-dimensional process, and neglecting both diffraction and refraction effects. An analytical application of Green’s law can only be made in case of simple bathymetries, monotonically increasing in the cross-shore direction and being longshore uniform. In the present work, a new formulation is proposed, based on Green’s law, for the direct calculation of the change in amplitude of a long wave that approaches the coast while traveling over a natural bathymetry, characterized by a general shape. Hence, the effects due to the ray curvature provided by the refraction/diffraction phenomena are accounted for. In detail, a generalization of Green’s law is proposed by introducing a numerically computed coefficient. Comparisons have been provided between the wave amplitude evolution, reconstructed using the proposed law, and the results of numerical simulations, run using a solver based on the solution of the shallow water equations. Although local effects due to obstacles are not properly captured, such comparisons reveal that the generalized Green’s law works well in the far field under different wave and complex morphological conditions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273419 Collegamento a IRIS

2019
Dynamics of the Coastal Zone
JOURNAL OF MARINE SCIENCE AND ENGINEERING
Autore/i: Postacchini, M.; Romano, Alessandro
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/275983 Collegamento a IRIS

2019
Combining numerical simulations and normalized scalar product strategy: A new tool for predicting beach inundation
JOURNAL OF MARINE SCIENCE AND ENGINEERING
Autore/i: Postacchini, M.; Ludeno, G.
Classificazione: 1 Contributo su Rivista
Abstract: The skills of the Normalized Scalar Product (NSP) strategy, commonly used to estimate the wave field, as well as bathymetry and sea-surface current, from X-band radar images, are investigated with the aim to better understand coastal inundation during extreme events. Numerical simulations performed using a Nonlinear Shallow-Water Equations (NSWE) solver are run over a real-world barred beach (baseline tests). Both bathymetry and wave fields, induced by reproducing specific storm conditions, are estimated in the offshore portion of the domain exploiting the capabilities of the NSP approach. Such estimates are then used as input conditions for additional NSWE simulations aimed at propagating waves up to the coast (flood simulations). Two different wave spectra, which mimic the actual storm conditions occurring along the coast of Senigallia (Adriatic Sea, central Italy), have been simulated. The beach inundations obtained from baseline and flood tests related to both storm conditions are compared. The results confirm that good predictions can be obtained using the combined NSP-NSWE approach. Such findings demonstrate that for practical purposes, the combined use of an X-band radar and NSWE simulations provides suitable beach-inundation predictions and may represent a useful tool for public authorities dealing with the coastal environment, e.g., for hazard mapping or warning purposes.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/270375 Collegamento a IRIS

2019
Flood impact on masonry buildings: The effect of flow characteristics and incidence angle
JOURNAL OF FLUIDS AND STRUCTURES
Autore/i: Postacchini, Matteo; Zitti, Gianluca; Giordano, Ersilia; Clementi, Francesco; Darvini, Giovanna; Lenci, Stefano
Classificazione: 1 Contributo su Rivista
Abstract: Climate change and the raising number of extreme events, such as severe floods, has increased the attention on their effects on urban systems. Urban floods generate important hydrodynamic loads on building and this work proposes a first systematic study on the actions generated by floods with different characteristics (depth, velocity and incidence angle) on masonry buildings. The study is carried out with experimental tests reproducing a masonry bay with scale 1:10, while the effect of the flow hitting the building has been obtained by moving the building in the water at rest. The pressure generated by the fluid at the four walls of the building was recorded using pressure transducers. It has been found that the overpressure acting on the building depends on the flow characteristics in different manner for the frontal, lateral and rear walls. Further, the incidence angle plays a major role in the generation of a pressure gradient along the impacted wall, and significantly affects both peak frequency and spectral energy. Use of theoretical models suggests that (i) the drag coefficient of the building decreases with the Froude number, and only slightly depends on the incidence angle, and (ii) the blocking effect largely affects the hydrodynamics around the structure.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/266247 Collegamento a IRIS

2018
Normalized Scalar Product Approach for Nearshore Bathymetric Estimation from X-Band Radar Images: An Assessment Based on Simulated and Measured Data
IEEE JOURNAL OF OCEANIC ENGINEERING
Autore/i: Ludeno, Giovanni; Postacchini, Matteo; Natale, Antonio; Brocchini, Maurizio; Lugni, Claudio; Soldovieri, Francesco; Serafino, Francesco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/253030 Collegamento a IRIS

2018
FLOOD IMPACTS ON BUILDINGS: FIRST EXPERIMENTAL AND NUMERICAL RESULTS
Proceedings del XXXVI Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: Brocchini, Maurizio; Capozucca, Roberto; Clementi, Francesco; Darvini, Giovanna; Giordano, Ersilia; Lenci, Stefano; Postacchini, Matteo; Zitti, Gianluca
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263397 Collegamento a IRIS

2018
Wave-Current Interactions and Infragravity Wave Propagation at a Microtidal Inlet
e-Proceedings of the 3rd EWaS International Conference on "Insights of the Water-Energy-Food Nexus"
Autore/i: Melito, Lorenzo; Postacchini, Matteo; Sheremet, Alex; Calantoni, Joseph; Zitti, Gianluca; Darvini, Giovanna; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Recent studies have shown that wave blocking occurs at river mouths with strong currents typically preventing relatively short period sea and swell waves from propagating up the river. However, observations demonstrate that lower frequency waves, so-called infragravity waves, do pass through and propagate up the river, particularly during storm events. We present observations from the Misa River estuary of infragravity wave propagation up the river during storm conditions. A model of the complex nonlinear interactions that drive infragravity waves is presented. The results are discussed in the context of an observed river mouth bar formed in the lower reach of the Misa River.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/258992 Collegamento a IRIS

2018
ANALYSIS OF MIXING AT RIVER MOUTHS: THE ROLE OF MACROVORTICES AND SUB-GRID TURBULENCE
8th International Symposium on Environmental Hydraulics
Autore/i: Melito, Lorenzo; Postacchini, Matteo; Darvini, Giovanna; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: INTRODUCTION A good understanding of flow mixing is important for properly describing the morphodynamics of the nearshore and river mouths. In recent years the modeling of flow mixing in natural shallow water regions has seen improvement thanks to the increasing computational power and the development of reliable and feasible models for large eddies and sub-grid turbulence. We here investigate the interplay between macrovortices, i.e. large-scale vortices with vertical axes, typical of shallow water flows, and the sub-grid turbulence characterizing river mouth flows, where a river current interacts with incoming sea waves. Generation of macrovortices is ensured by differential breaking at an estuarine shoal, whose presence also allows for inspection of the role of complex bathymetries (Olabarrieta et al., 2014). To this end, numerical simulations of wave-current interaction are performed by means of a solver for wave propagation in shallow water by Brocchini et al. (2001), integrated with a simple Horizontal Large Eddy Simulation (HLES) model proposed by Grosso et al. (2007). THE NUMERICAL MODEL The numerical model used for the tests (Brocchini et al., 2001) is based on the Nonlinear Shallow Water Equations (NSWE) and implements the finite-volume Weighted Averaged Flux method. The model is modified to give account of the dynamics induced by a river discharging at sea, and allows for computation of the morphological evolution of the bottom through the weak hydro-morphodynamic coupling proposed by Postacchini et al. (2012). The model also implements a simple HLES model to consider, in an approximate fashion, the dissipative terms due to sub-grid turbulence, which would, otherwise, be neglected by a classic approach of the NSWE (Grosso et al., 2007). THE TESTS Similarly to the wave-current interaction tests performed in the work of Olabarrieta et al. (2014), we reproduce the interaction of a steady river jet with weak-to-strong waves over a bathymetry characterized by a large river mouth shoal, and the generation, organization and migration of macrovortices as function of the sub-grid turbulence (HLES eddy viscosity varied between 0 and 0.1). THE RESULTS The numerical simulations reveal a significant generation and offshore advection of macrovortices at the seaward edge of the mouth shoal. Important turbulent structures are also observed, during the initial stages of the motion, at the corners of the inlet mouth, where the canalized, intense river current spreads over the shoal and interacts with the quiescent sea waters; these transient vortices dissipate fairly rapidly. The activation of the HLES model does not seem to have significant effects on the transient inlet vortices, causing only a limited decrease in their intensity as the sub-grid turbulence increases. Conversely, the shoal macrovortices are more sensible to changes in sub-grid turbulence: their intensity sensibly decreasing as the eddy viscosity increases. Notably, use of eddy viscosity parameters of the order 10-1 suppresses the generation of macrovortices in the shoal zone. Further considerations on these mechanisms will be illustrated at the conference.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/270377 Collegamento a IRIS

2018
METODI E MODELLI PER L’ANALISI DELL’INONDAZIONE COSTIERA: UNO STUDIO PER LA BAIA DI ALGHERO
Atti del XXXVI Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: Lalli, Francesco; Bruschi, Antonello; Luisa Cassese, Maria; Di Manna, Pio; Lisi, Iolanda; Vittori, Eutizio; Memmola, Francesco; Postacchini, Matteo; Bellafiore, Debora; Bajo, Marco; Boy, Alessandra; Pillai, Alessandra; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263428 Collegamento a IRIS

2018
BATHYMETRY AND WAVE FIELD ESTIMATE USING A RADAR/NSP APPROACH: A NUMERICAL ANALYSIS
Atti del XXXVI Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: Ludeno, Giovanni; Postacchini, Matteo; Lugni, Claudio; Soldovieri, Francesco; Serafino, Francesco; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263429 Collegamento a IRIS

2018
MODELLING HUMAN MOTION IN FLOOD EVACUATION: PRELIMINARY EXPERIMENTAL RESULTS
Atti del XXXVI Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: Postacchini, Matteo; Ascenzi, MARIA BEATRICE; Bruni, Ramona; Finizio, Fiorenza; Bernardini, Gabriele; Quagliarini, Enrico; Brocchini, Maurizio; D'Orazio, Marco
Classificazione: 2 Contributo in Volume
Abstract: Human behaviors in flood emergency affect individuals’ safety levels in urban scenarios. Evacuation simulators are needed to fully perform risk assessment and risk-reduction solutions evaluations. Volunteers are engaged in laboratory experiments to propose floodwaters-evacuation motion relations. A mannequin (representing an adult) is used for determining human stability limits in floodwaters. Preliminary results are compared to previous works and relations could be added to evacuation simulators.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/263430 Collegamento a IRIS

2018
Waves and Currents at a River Mouth: The Role of Macrovortices, Sub-Grid Turbulence and Seabed Friction
WATER
Autore/i: Melito, Lorenzo; Postacchini, Matteo; Darvini, Giovanna; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: Numerical experiments of wave-current interaction have been performed to investigate the evolution and dissipation of horizontal large-scale vortical structures generated by differential wave breaking and current shearing at river mouths. Specific focus is on the role played by turbulence of scales smaller than the water depth and by seabed friction on the dissipation of the mentioned macrovortices. The analysis reveals two regions of turbulence generation: at the river mouth, and along the curved seaward boundary of the shoal. In the latter zone, macrovortices are formed due to differential wave breaking induced by the sudden variation in water depth and enhanced by opposing currents which favour wave steepening. Such vortices are then advected towards the shore. Among the dissipative mechanisms, dissipation induced by seabed friction is deemed dominant, in particular in the most shallow waters of the shoal. Sub-grid turbulence dissipation, conversely, is more efficient offshore, although exerting some effect also over the shoal when supported by the continuous action of waves.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/258065 Collegamento a IRIS

2017
A preliminary combined simulation tool for the risk assessment of pedestrians' flood-induced evacuation
ENVIRONMENTAL MODELLING & SOFTWARE
Autore/i: BERNARDINI, GABRIELE; POSTACCHINI, MATTEO; QUAGLIARINI, ENRICO; BROCCHINI, MAURIZIO; CIANCA, CATERINA; D'ORAZIO, Marco
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/251392 Collegamento a IRIS

2017
Comparison between the wintertime and summertime dynamics of the Misa River estuary
MARINE GEOLOGY
Autore/i: Brocchini, Maurizio; Calantoni, Joseph; Postacchini, Matteo; Sheremet, Alex; Staples, Tracy; Smith, Joseph; Reed, Allen H.; Braithwaite III, Edward F.; Lorenzoni, Carlo; Russo, Aniello; Corvaro, Sara; Mancinelli, Alessandro; Soldini, Luciano
Classificazione: 1 Contributo su Rivista
Abstract: The Misa River on the Italian Adriatic coast is typical of the rivers that drain the Apennine Mountain range. The focus of this study, conducted in the late summer of 2013 and mid-winter of 2014, was to contrast the general wintertime-summertime dynamics in the Misa River estuarine systemrather than investigate specific dynamical features (e.g. offshore sediment transport, channel seiche, and flocculation mechanisms). Summertime conditions of the Misa River estuary are characterized by low freshwater discharge and net sediment deposition whereas, in the wintertime, the Misa River and estuary is characterized by high episodic freshwater discharge and net erosion and sediment export. Major observed differences between wintertime-summertime dynamics in the Misa River and estuary are a result of seasonal-scale differences in regional precipitation and forcing conditions driven largely by the duration and intensity of prevailing wind patterns that frequently change direction in summertime while keep almost constant directions for much longer periods in wintertime, thus generating major sea storms. Sediment deposition was observed in the final reach of the Misa River and estuary in the summertime. However, in the wintertime, large flood events led to sediment erosion and export in the final reach of the Misa River and estuary that, in conjunction with storm-wave-induced mud transport, led to sediment deposition at the river entrance and in the adjacent nearshore region. The seasonal cyclic pattern of erosion and deposition was confirmedwith bathymetric surveys of the final reach of the estuarine region. A critical component for the balance between summertime deposition and wintertime erosion was the presence of an underlying mat of organic deposits that limited the availability of sediments for erosion in winter, when massive debris transport occurs. Further, suspended cohesive sediments flocs were subjected to smaller hydrodynamic stresses in the summertime favoring depositionwithin the estuary. Conversely, during wintertime storms, flocswere subjected to larger hydrodynamic stresses favoring breakup into smaller flocs and deposition outside the estuary.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247010 Collegamento a IRIS

2017
Medium-term dynamics of a Middle Adriatic barred beach
OCEAN SCIENCE
Autore/i: POSTACCHINI, MATTEO; SOLDINI, Luciano; LORENZONI, CARLO; MANCINELLI, ALESSANDRO
Classificazione: 1 Contributo su Rivista
Abstract: In recent years, attention has been paid to beach protection by means of soft and hard defenses. Along the Italian coast of the Adriatic Sea, sandy beaches are the most common landscape feature and around 70% of the Marche region's coast (central Adriatic) is protected by defense structures. The longest free-from-obstacle nearshore area in the region includes the beach of Senigallia, frequently monitored in the last decades and characterized by a multiple bar system, which represents a natural beach defense. The bathymetries surveyed in 2006, 2010, 2011, 2012 and 2013 show long-Term stability, confirmed by a good adaptation of an analyzed stretch of the beach to the Dean-Type equilibrium profile, though a strong short-to medium-Term variability of the wave climate has been observed during the monitored periods. The medium-Term dynamics of the beach, which deal with the evolution of submerged bars and are of the order of years or seasons, have been related to the wave climate collected, during the analyzed temporal windows, by a wave buoy located about 40ĝ€km off Senigallia. An overall interpretation of the hydrodynamics, sediment characteristics and seabed morphology suggests that the wave climate is fundamental for the morphodynamic changes of the beach in the medium term. These medium-Term time ranges during which waves mainly come from NNE/ESE are characterized by a larger/smaller steepness and by a larger/smaller relative wave height, and seem to induce seaward/shoreward bar migration as well as bar smoothing/steepening. Moving southeastward, the bar dimension increases, while the equilibrium profile shape suggests the adaptation to a decreasing sediment size in the submerged beach. This is probably due to the presence of both the harbor jetty and river mouth north of the investigated area.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247218 Collegamento a IRIS

2017
Snow avalanches striking water basins: behaviour of the avalanche’s centre of mass and front
NATURAL HAZARDS
Autore/i: ZITTI, GIANLUCA; Ancey, C.; POSTACCHINI, MATTEO; BROCCHINI, MAURIZIO
Classificazione: 1 Contributo su Rivista
Abstract: We study the behaviour of a low-density granular material entering a water basin by means of a simplified two-dimensional model, with the aim to understand the dynamics of a snow avalanche impacting a water basin like an alpine lake or a fjord. The low density of the impacting mass induces an uplift buoyancy force and, consequently, a complicated interaction between the solid and fluid phase. This paper provides an insight into the motion of the impacting mass, by presenting a simplified, two-dimensional model, where the snow is described by a low-density granular material. First, small-scale experiments, based on the Froude similarity with snow avalanches, are used to evaluate the motion of reference points of the impacting mass, i.e. the front (F), centre of mass (C) and deepest point (L). Then, applying the mass and momentum conservation principles to a fixed volume, we show that the mean motion of the impacting mass is similar to that of a damped oscillator. The stretch of the impacting mass motion is described through the motion of the reference points F and L.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/248897 Collegamento a IRIS

2016
Escosed: Observations of Morphodynamics during Bora at the Mouth of the Misa River
International Conference on Multiphase Flow - ICMF 2016
Autore/i: Calantoni, J.; Sheremet, A.; Brocchini, Maurizio; Postacchini, Matteo
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The shallow mouth of the Misa River, Senigallia, Italy is exposed to wind and waves from the Adriatic Sea and is vulnerable to morphodynamic activity during even moderate storm events (e.g., winter Bora). Sediment loads and transport patterns may be strongly influenced by the confluence of fine cohesive suspended sediment contained in the discharge from the river mixing with coarser sandy material stirred up by waves impinging on the river mouth. Observations of rapid changes in bed elevation along a transect extending offshore of the river mouth were made using a combination of instruments deployed from 23-27 January 2014 at two locations in roughly 5 m water depth and 6 m water depth. At the 5 m water depth location over 0.4 m of deposition was observed roughly during a 6-hour period. Similarly, at the 6 m water depth location nearly 0.2 m of deposition was observed roughly over a 6-hour period with approximately a two-hour time lag. The onset of deposition was concurrent with a change in direction of the mean currents at both locations and a change in direction of wave skewness observed at the 5 m water depth location. We hypothesize that sandbar migration was responsible for the observed changes in bed elevation at both locations. Our analysis will focus on sediment transport modeling to explain rates of deposition and time lag of the observed changes in bed elevation at the 5 m and 6m water depth locations.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247228 Collegamento a IRIS

2016
HYDRODYNAMICS OF A MUDDY ESTUARINE ENVIRONMENT: SUMMERTIME VS WINTERTIME CONDITIONS
The 12th International Conference on Hydrodynamics
Autore/i: Brocchini, Maurizio; Calantoni, Joseph; Postacchini, Matteo; Reed, Allen; Lorenzoni, Carlo; Mancinelli, Alessandro
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The hydrodynamics of an estuarine environment characterized by cohesive sediments, has been studied through a pair of experimental campaigns performed at the mouth of the Misa River. The Misa River flows from the Apennine Mountains and enters the Adriatic Sea in Senigallia, a tourist town located on the Mid-East coast of Italy. The estuary of the Misa River has characteristics of a field-scale laboratory; the final reach is highly engineered with containment structures. Consequently, it was chosen as a suitable site for the experiments undertaken during the EsCoSed (“Estuarine Cohesive Sediment”) Project. The estuarine environment of the Misa River was observed during both summertime and wintertime experiments. The hydrodynamics was monitored using both Eulerian (e.g., bottom moored platforms at both the river-bed and sea-bed with high-resolution ADCPs recording velocity profiles) and Lagrangian (e.g., surface drifters) instrumentation, allowing for the characterization of the flow field during very different flow conditions. The climate occurring before and during the investigated periods has also been analyzed through use of numerical simulations, wave buoy measurements, and tide gauges. A comparative analysis between summertime and wintertime conditions, focused on wave-current forcing and local estuarine hydrodynamics, is underway. The preliminary results highlight the control of wind direction on the observed hydrodynamics. During the summertime the wind frequently changes direction. Conversely, during wintertime the wind direction remains fairly constant leading to severe storms. The extreme wintertime events generate intense sediment transport driving morphologic change.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247222 Collegamento a IRIS

2016
Condizioni al Contorno di Riva Morfodinamiche: Alcuni Aspetti della Metodologia di Validazione
Atti del XXXV Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: Perugini, E.; Postacchini, Matteo; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247227 Collegamento a IRIS

2016
Numerical simulations on run-up of wave groups for different beach profiles
Proceedings of the 7th International Short Conference on Applied Coastal Research - SCACR
Autore/i: Soldini, L.; Postacchini, M.; Lorenzoni, C.
Editore: EdiBios, Cosenza, Italy
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/246467 Collegamento a IRIS

2016
Advances in numerical modelling of swash zone dynamics
COASTAL ENGINEERING
Autore/i: Briganti, Riccardo; Torres Freyermuth, Alec; Baldock, Tom E.; Brocchini, Maurizio; Dodd, Nicholas; Hsu, Tian Jian; Jiang, Zhonglian; Kim, Yeulwoo; Pintado Patiño, Jose Carlos; Postacchini, Matteo
Classificazione: 1 Contributo su Rivista
Abstract: We present a comprehensive and critical review of work on the numerical modelling of swash zone processes between 2005 and 2015. A wide range of numerical models has been employed for the study of this region and, hence, only phase-resolving approaches (i.e., depth-averaged and depth-resolving models) are analyzed. The current advances in the modelling of swash zone processes are illustrated by comparing different numerical models against laboratory experiments of a dam-break-driven swash event. Depth-averaged and depth-resolving models describe well the swash flow for both coarse sand and gravel impermeable beach cases. Depth-averaged models provides a practical tool for engineering use, whereas depth-resolving models improve the flow description, especially for the backwash phase, with a significantly higher computational cost. The evolution and magnitude of bed shear stresses predicted by all models is reasonable when compared with laboratory estimates based on the log-law. However, differences between modelling approaches cannot be rigorously evaluated owing to the uncertainty in shear stress estimates while employing such approximation. Furthermore, small-scale processes, such as turbulence evolution, are investigated with depth-resolving models, finding differences between the two-dimensional and three-dimensional approaches. Numerical models allow us to investigate other processes such as beach morphology changes, the evolution of the turbulence coherent structures, and the infiltration/exfiltration effects on the swash flow. A discussion on the advantages and limitations of each model is presented. The future of swash zone modelling depends on the increase of the computational power and, more importantly, on the improvement of the current capability to obtain intra-wave measurements for model validation, calibration, and greater resolution of physical processes.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236355 Collegamento a IRIS

2016
Lagrangian Observations of Waves and Currents From the River Drifter
IEEE JOURNAL OF OCEANIC ENGINEERING
Autore/i: POSTACCHINI, MATTEO; Centurioni, L. R.; Braasch, L.; BROCCHINI, MAURIZIO; Vicinanza, D.
Classificazione: 1 Contributo su Rivista
Abstract: The working principle and the capabilities of a new platform called the River Drifter are here presented. This technology has applications in the study of the hydrodynamics of coastal areas, rivers, and lakes. The River Drifter was designed for shallow water applications (1 m and deeper) to collect concurrent measurements of surface currents, three-dimensional velocity profiles underneath the device, water depth, and salinity. Here, we discuss how water level displacements can be inferred and used to measure the swell characteristics and to also correct the measured velocity. We also show how the local vorticity field can be computed. As an example application, we describe a study whose goal was to investigate the fate of a polluted river plume and how two River Drifters initially following the same path are characterized by very different final trajectories. The different behaviors of the two drifters are explained in terms of the local flow dynamics, which are strongly influenced by the seabed morphology, forcing the River Drifters to move in different directions.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/235745 Collegamento a IRIS

2016
Impulse waves generated by snow avalanches: Momentum and energy transfer to a water body
JOURNAL OF GEOPHYSICAL RESEARCH. EARTH SURFACE
Autore/i: Zitti, Gianluca; Ancey, Christophe; Postacchini, Matteo; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: When a snow avalanche enters a body of water, it creates an impulse wave whose effects may be catastrophic. Assessing the risk posed by such events requires estimates of the wave’s features. Empirical equations have been developed for this purpose in the context of landslides and rock avalanches. Despite the density difference between snow and rock, these equations are also used in avalanche protection engineering. We developed a theoretical model which describes the momentum transfers between the particle and water phases of such events. Scaling analysis showed that these momentum transfers were controlled by a number of dimensionless parameters. Approximate solutions could be worked out by aggregating the dimensionless numbers into a single dimensionless group, which then made it possible to reduce the system’s degree of freedom. We carried out experiments that mimicked a snow avalanche striking a reservoir. A lightweight granular material was used as a substitute for snow. The setup was devised so as to satisfy the Froude similarity criterion between the real-world and laboratory scenarios. Our experiments in a water channel showed that the numerical solutions underestimated wave amplitude by a factor of 2 on average. We also compared our experimental data with those obtained by Heller and Hager (2010), who used the same relative particle density as in our runs, but at higher slide Froude numbers.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247020 Collegamento a IRIS

2016
Experimental study of the short-term efficiency of different breakwater configurations on beach protection
JOURNAL OF OCEAN ENGINEERING AND MARINE ENERGY
Autore/i: LORENZONI, CARLO; POSTACCHINI, MATTEO; BROCCHINI, MAURIZIO; MANCINELLI, ALESSANDRO
Classificazione: 1 Contributo su Rivista
Abstract: A campaign of experimental tests on a 2D movable-bed physical model, reproducing an Italian beach on the Adriatic Sea, has been performed in the wave flume of the “Laboratorio di Idraulica e Costruzioni Marittime” of the Università Politecnica delle Marche (Ancona, Italy), with the aim to assess the fundamental features of various breakwater configurations to be used in a beach-defence system typical of sandy, low-coastline beaches. Three emerged and three submerged configurations of rubble-mound detached breakwaters, for beach protection, placed at different distances from the shore, were tested, as well as a free beach configuration. The short-term hydrodynamic performances of the different configurations were assessed using as forcing some typical real-life intense sea-storm conditions. Wave transmission and beach protection efficiency under various intense wave conditions were obtained and related to some dimensionless parameters, amongst which a recently introduced one, χ, that combines both wave and breakwater properties. Transmission coefficients were found to be about 0.4 for emerged breakwaters and in the range 0.5–0.8 for submerged breakwaters. A net damping coefficient, defined as the wave height decay solely due to the effect of the breakwater, was measured as 0.2 for submerged breakwaters and 0.4 for the emerged ones. Further, submerged breakwaters induce an inshore mean water superelevation that increases with χ, whilst it decreases in the case of emerged breakwaters. Wave transmission is well represented by existing literature relations for both emerged and submerged breakwaters. Emerged breakwaters are more protective than submerged ones, but, at the same time, are more sensitive to changes in structure dimensions or positions. This is confirmed by the analysis of the momentum flux within the nearshore region, which is much larger for the submerged breakwaters. Such structures induce large swash-zone motions and sediment transport, comparable to those occurring at an unprotected beach.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247212 Collegamento a IRIS

2016
Assessing the Hydro-Morphodynamic Response of a Beach Protected by Detached, Impermeable, Submerged Breakwaters: A Numerical Approach
JOURNAL OF COASTAL RESEARCH
Autore/i: POSTACCHINI, MATTEO; RUSSO, ANIELLO; CARNIEL, SANDRO; BROCCHINI, MAURIZIO
Classificazione: 1 Contributo su Rivista
Abstract: Coastal areas host a large fraction of the world's population and are exposed to natural extreme events, which are a serious threat to human life, as well as to economies. For this reason, sea storms are increasingly the object of studies, and the design of traditional coastal defenses is being carried out in conjunction with modeling analyses. Relying on numerical simulations performed by means of an innovative shallow-water hydro-morphodynamic model, the present work explores the overall response of a protected beach to sea storms. Numerical tests evaluate the effects of sea states extracted from realistic sea storms having different spectral characteristics, as well as the influence on beach morphology of positioning shore-parallel, impermeable, submerged breakwaters. Simulation results revealed that, while erosion/accretion patterns depend weakly on the different sea state conditions, the morphodynamics induced around the barriers is strongly influenced by the breakwaters' positioning. More specifically, at least for the forcing here analyzed, bed variations were shown to increase when the structures are progressively located offshore; on the other hand, the swash zone morphology seems to be only weakly influenced by the positioning of the breakwaters. We also observed that for an increasing extension of the volume over which dissipative breaking mechanisms occur, a decreasing inshore erosion is accompanied by an equally fast decrease of offshore erosion. Analysis of the vorticity fields shows that breakwaters placed far from the shoreline induce an evolution of the vortices generated by breaking waves rather different from the one due to breakwaters placed closer to the shoreline (which can induce seaward flows through the gap, like rip currents).
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/236356 Collegamento a IRIS

2016
Experiments on the impact of snow avalanches into water
Sustainable Hydraulics in the Era of Global Change - Proceedings of the 4th European Congress of the International Association of Hydroenvironment engineering and Research, IAHR 2016
Autore/i: Zitti, G.; Ancey, C.; Postacchini, M.; Brocchini, M.
Editore: CRC Press/Balkema
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The number of anthropized reservoirs threatened by snow avalanches is steadily increasing and impulse waves caused by avalanche impact are becoming a considerable risk for such basins. The dynamics of the impact of a snow avalanche into a water body is studied through laboratory experiments, where a granular material, with solid density slightly lower than that of the water, is used to simulate the buoyant behaviour of the snow. The proposed experimental model shares many similarities with those used to investigate the impact of landslides into water bodies (e.g., see Fritz et al. 2003a, Fritz et al. 2003b), but it also clarifies the differences between the impact of an avalanche and that of a landslide: while a landslide typically reaches the bottom of the water body, because of its high constant density, in the present experiments a floating motion of the impacted mass has been observed. The wave generation and its propagation are acquired by high-frequency cameras placed along the flume. Some preliminary results on wave amplitude/height decay and on wave celerity state the strongly non-linear behaviour of the generated wave. Further, their comparison with the corresponding predictive relations proposed for the case of landslides (Heller and Hager 2010) highlights a different wave decay and celerity evolution in the proximity of the impact.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247223 Collegamento a IRIS

2015
The EsCoSed Project: Summertime-Wintertime Evolution of the Misa River Estuarine Environment
Atti del XXII Congresso AIMETA
Autore/i: Maurizio BROCCHINI; Joseph CALANTONI; Allen H. REED; Alex SHEREMET; Tracy STAPLES; Joseph SMITH; Matteo POSTACCHINI; Ed BRAITHWAITE; Tim KOONEY; Carlo LORENZONI; Aniello RUSSO; Alessandro MANCINELLI; Luciano SOLDINI; Sara CORVARO; Alessandro COLUCCELLI; Paolo PARONCINI
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233514 Collegamento a IRIS

2015
Technical Note: Medium-term morphodynamics in an unprotected sandy beach of the Adriatic Sea
OCEAN SCIENCE DISCUSSIONS
Autore/i: Postacchini, Matteo; Soldini, Luciano; Lorenzoni, Carlo; Mancinelli, Alessandro
Classificazione: 1 Contributo su Rivista
Abstract: Abstract. In the recent years attention has been paid to the beach protection by means of soft and hard defenses. Along the Italian coasts of the Adriatic Sea, sandy beaches are the most common landscapes and around 70 % of the Marche-Region coasts (central Adriatic), is protected by defense structures. The longest free-from-obstacle nearshore area in the Region includes the beach of Senigallia, characterized by a multiple barred beach, frequently monitored during the last decades. The bathymetries surveyed in 2006, 2010, 2011, 2012 and 2013 show a good adaptation of the beach to the Dean-type equilibrium profile, though a strong short-/medium-term variability of the wave climate has been observed during the monitored periods. This suggests a slight influence of wave forcing on the long-term profiles, which seems to only depend on the sediment size. Further, the medium-term dynamics of the submerged bars and their geometric features have been related to the wave climate collected by a wave buoy located 40 km off Senigallia during the analyzed temporal windows. An overall interpretation of the complete dynamics, i.e. hydrodynamics (buoy data), sediment characteristics (equilibrium-profile A parameter) and morphodynamics (bathymetric surveys), suggests that the wave climate is fundamental for the morphodynamic changes of the beach in the medium term: waves coming from NNE/ESE are characterized by a larger/smaller steepness and induce seaward/shoreward bar migration, as well as bar smoothing/steepening. Moving southward, the bar dimension increases, while the equilibrium profile suggests a decrease of the sediment size in the submerged beach, this probably due to the presence of both harbor jetty and river mouth North of the investigated area.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233462 Collegamento a IRIS

2015
Impulse waves generated by snow avalanches falling into lakes
E-proceedings of the 36th IAHR World Congress
Autore/i: Zitti, Gianluca; Ancey, Christophe; Postacchini, Matteo; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In recent years, the number of water reservoirs in high-altitude areas has increased. They are often used to provide water for various activities related with recreational (i.e. skiing) and production activities. Many of such reservoirs are threatened by snow avalanches. To investigate the phenomenon, an experimental study was carried out at the Ecole Polytechnique Fédérale de Lausanne using a prismatic 3m-long flume. A mass of buoyant particles, initially at rest, was released into a water flume down a 30°-sloping ramp. Its impact with the water surface was analyzed in detail. During the tests, the impacting mass, the water depth in the flume and the ramp length were changed. Both the dynamics of the granular mass at the impact zone and the wave generation induced by the impact were acquired using a high-frequency camera and accurately analyzed. An analysis of the wave propagation along the flume, also captured by two lower-speed cameras, was made by mean of numerical analyses based on a depth-averaged Boussinesq-type model. A theoretical analysis has also been undertaken to assess how the sub-aerial mass dynamics influences energy dissipation, and to identify the key variables of the problem, i.e. the velocity at impact, the shape of the water volume displaced during the impact, the depth of the center of the submerged mass and the percentage of submerged mass.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247225 Collegamento a IRIS

2015
Long-term and short-term morphodynamics in an unprotected sandy beach of the Adriatic Sea
GEOPHYSICAL RESEARCH ABSTRACTS
Autore/i: Postacchini, Matteo; Soldini, Luciano; Mancinelli, Alessandro; Lorenzoni, Carlo
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/229985 Collegamento a IRIS

2015
Morphodynamic shoreline boundary conditions: A preliminary validation from laboratory experiments
Proceedings of the International Offshore and Polar Engineering Conference
Autore/i: Brocchini, Maurizio; Postacchini, Matteo
Editore: International Society of Offshore and Polar Engineers
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: At present the processes occurring in the Swash Zone (SZ) are disregarded by all available wave-averaged nearshore circulation models. Only recently a series of studies has proposed an approach to solve this problem by means of Shoreline Boundary Conditions (SBCs) obtained from integrating the Nonlinear Shallow Water Equations over the SZ width. While hydrodynamic conditions are a consolidated and validated theoretical tool, morphodynamic conditions (MSBCs) still require theoretical inspection and experimental validation. We here focus on a theoretical analysis of the problem, which, on the basis of available experimental data, aims at clarifying the role of short- and long-wave contributions to the mentioned MSBCs.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247224 Collegamento a IRIS

2015
Scour depth under pipelines placed on weakly cohesive soils
APPLIED OCEAN RESEARCH
Autore/i: POSTACCHINI, MATTEO; BROCCHINI, MAURIZIO
Classificazione: 1 Contributo su Rivista
Abstract: We here study the scouring processes that evolve around a submarine pipeline placed on a weakly cohesive seabed. We first analyze some laboratory tests carried out by Vijaya Kumar et al. [21], Xu et al. [25] and Zhou et al. [28] that focused on the scouring around a horizontal cylinder lying on a cohesive bed, subject to waves and currents. The specific purpose is that of finding a new formula for the prediction of the equilibrium scour depth under submarine pipelines. After a theoretical analysis of the main parameters, the sought formula has been found to be a function of: (i) the hydrodynamic forces acting on the cylinder (through the Keulegan-Carpenter parameter KC), (ii) the clay content of the soil C-c, and (iii) the burial depth eo ID. In the presence of small amounts of clay (C-c< 5%), the scour depth depends directly on KC (as confirmed by many literature works for pipelines lying on sandy soils, e.g.[18]) and inversely on C-c (as already seen for bridge abutments on cohesive soils, e.g. [1]), the best-fit law being characterized by a coefficient of determination R-2 = 0.62. If some burial depth is accounted for, this being a novelty of the present work, a more general formulation can be used, valid in the presence of weakly-cohesive soils and with burial depths of the pipe smaller than 0.5 (R-2 = 0.79). For large clay-content ranges (2% < 75 %), the scour depth depends directly on both KC and C-c, this giving R-2 = 0.79 (no burial depth) and 0.91 (some burial depth). However, this finding is at odds with the main literature, because, for large amounts of clay, it is fundamental to consider the liquidity index LI, which accounts for some important clay properties, like the plasticity. We argue that the absence of LI is balanced by the direct dependence of the scour depth on C-c. Notwithstanding the small number of available data, a formula for the prediction of the scour depth under pipelines lying on cohesive soils is fundamental for several engineering applications. The present contribution represents the first attempt to build such a formula, when the pipeline is subject to the wave-current forcing and the seabed is characterized by a relatively small clay content.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/227974 Collegamento a IRIS

2015
Summertime conditions of a muddy estuarine environment: the EsCoSed project contribution
WATER SCIENCE AND TECHNOLOGY
Autore/i: BROCCHINI, MAURIZIO; Calantoni, J.; Reed, A. H.; POSTACCHINI, MATTEO; LORENZONI, CARLO; RUSSO, ANIELLO; MANCINELLI, ALESSANDRO; CORVARO, SARA; MORICONI, GIACOMO; SOLDINI, Luciano
Classificazione: 1 Contributo su Rivista
Abstract: As part of the Estuarine Cohesive Sediments (EsCoSed) project, a field experiment was performed in a highly engineered environment, acting as a natural laboratory, to study the physico-chemical properties of estuarine sediments and the associated hydro-morphodynamics during different seasons. The present contribution focuses on the results obtained from the summertime monitoring of the most downstream part of the Misa River (Senigallia, Italy). The measured hydrodynamics suggested a strong interaction between river current, wave forcing and tidal motion; flow velocities, affected by wind waves traveling upstream, changed significantly along the water column in both direction and magnitude. Surficial salinities in the estuary were low in the upper reaches of the estuary and exceeded 10 psu before the river mouth. Montmorillonite dominated the clay mineral assemblage, suggesting that large, low density flocs with high settling velocities (> 1 mms(-1)) may dominate the suspended aggregate materials.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/226471 Collegamento a IRIS

2015
Whole-wavelength description of a wave boundary layer with permeable wall
EXPERIMENTS IN FLUIDS
Autore/i: Miozzi, M.; Postacchini, Matteo; Corvaro, Sara; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: This paper describes the whole-wavelength, highly resolved velocity field statistics in an oscillatory boundary layer driven by gravity waves, evolving on both impermeable and permeable beds. Velocity data from PTV measurements are acquired in a small window and then extended to the whole wavelength by means of a new phase-locked slotting technique. This technique increases the robustness of statistics and resolution by improving the number of the data samples available for each spatial cell in the Eulerian representation of the oscillatory boundary layer. The into-and out-of-bed volume flux is evaluated and its effects on the velocity field are reported, together with its influence on vorticity evolution. The presence of coherent structures embedded in a shear-dominated scenario is emphasized. The Lagrangian flow features extracted by PTV are presented in the context of the generalized Lagrangian-mean theory. The Stokes drift vertical profile is estimated by comparing the Eulerian and Lagrangian velocities. A critical height-separating region where the volume flux due to ventilation has different effects on both orbital amplitudes and Stokes drift is found. This distance corresponds to the maximum height of the still-attached vorticity layer.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/227975 Collegamento a IRIS

2014
Whole-wavelength description of a gravity-wave-driven flow over permeable beds
Proceeding of the "17th International Symposium on Applications of Laser Techniques to Fluid Mechanics"
Autore/i: Miozzi, Massimo; Corvaro, Sara; Postacchini, Matteo; Brocchini, Maurizio
Editore: Instituto Superior Tecnico, Lisboa, Portugal
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/233411 Collegamento a IRIS

2014
L’EVOLUZIONE DELLA COSTA NEL BREVE E LUNGO PERIODO: IL CASO DI SENIGALLIA (AN)
Monitoring of Mediterranean Coastal Areas: problems and measurements tecqniques
Autore/i: L. Soldini; M. Postacchini; C. Lorenzoni; A. Mancinelli
Editore: CNR - IBIMET, Firenze
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/221313 Collegamento a IRIS

2014
Uno studio a scala naturale dell'idro-morfodinamica estuarina: esperimenti di campo alla foce del fiume Misa
XXXIV Convegno Nazionale Idraulica e Costruzioni Idrauliche
Autore/i: Brocchini M.; Colantoni J.; Postacchini M.; Reed A.H.; Lorenzoni C.; Mancinelli A.; Soldini L.; Corvaro S.; Russo A.; Moriconi G.; Coluccelli A.; Paroncini P.; Ortenzio F.; Busca C.
Editore: Zaccaria Editore
Luogo di pubblicazione: Napoli
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205867 Collegamento a IRIS

2014
L’influenza delle opere sommerse nella morfodinamica costiera: uno studio numerico
STUDI COSTIERI
Autore/i: Postacchini, Matteo
Classificazione: 1 Contributo su Rivista
Abstract: Negli ultimi anni, le mareggiate risultano avere un impatto sempre più importante sull’economia dei litorali, incidendo pesantemente anche sul mantenimento delle strutture ricettive/turistiche, specialmente se hanno luogo nel periodo estivo. La progettazione delle tradizionali opere di difesa della costa risulta determinante nella protezione di tali strutture. Per questo motivo sono state effettuate alcune simulazioni mediante un solutore numerico idro-morfodinamico che risolve le equazioni delle acque basse e l’equazione di Exner. Sono stati realizzati test numerici con lo scopo di valutare i) l’effetto di mareggiate reali con diverse caratteristiche spettrali e ii) l’influenza della distanza da riva di una coppia di scogliere sommerse sulla morfologia della spiaggia. I risultati delle simulazioni hanno evidenziato una variazione minima nelle forme di erosione/accrescimento al variare delle caratteristiche spettrali delle mareggiate. La morfodinamica che si realizza intorno alle scogliere e nel varco è invece fortemente influenzata dalla posizione delle opere: le variazioni del fondale sono tanto maggiori, quanto più lontane sono le opere da terra. La zona di battigia, invece, è poco influenzata dalla distanza da riva delle scogliere.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247221 Collegamento a IRIS

2014
A natural-scale study of cohesive sediment transport: The Misa River case
RIVER FLOW 2014 - Proceedings of the International Conference on Fluvial Hydraulics
Autore/i: Brocchini M.; Russo A.; Calantoni J.; Reed A.H.; Postacchini M.; Lorenzoni C.; Corvaro S.; Mancinelli A.; Moriconi G.; Soldini L.
Editore: CRC Press
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/205869 Collegamento a IRIS

2014
Vorticity generation due to cross-sea
JOURNAL OF FLUID MECHANICS
Autore/i: M. Postacchini; M. Brocchini; L. Soldini
Classificazione: 1 Contributo su Rivista
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/166702 Collegamento a IRIS

2014
A wave-by-wave analysis for the evaluation of the breaking-wave celerity
APPLIED OCEAN RESEARCH
Autore/i: Postacchini M.; Brocchini M.
Classificazione: 1 Contributo su Rivista
Abstract: The paper gives an overall description of the breaking-wave celerity on the basis of a wave-by-wave analysis that has been performed by using field data collected during the ECORS Project (Truc Vert Beach, France, 2008). Data coming from two pressure sensors have been analyzed with the aim to correlate, after a zero-crossing analysis, each wave of both signals. The method is based on a first correlation between 10 ' time windows of both signals and, then, on the individuation of the correct time lag for each wave. Such data, which reveals a quasi-gaussian behavior of the breaking wave celerity, have also been used to relate the wave celerity with suitable wave characteristics, and comparisons are made with the most common formulas that can be found in the literature. The wave-by-wave method, validated by means of suitable laboratory test data, gives good results in the evaluation of the celerity, especially when it is made to depend on both a velocity scale and the wave non-linearity parameter. Further, a comparison with literature models used for the prediction of breaking wave celerity suggests good performances of both solitary-wave (correlation coefficient R-2 = 0.79) and shock-wave (R-2 = 0.71) theories, that give results well matched to the field data.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/188303 Collegamento a IRIS

2014
Fluid-particle interaction and generation of coherent structures over permeable beds: an experimental analysis
ADVANCES IN WATER RESOURCES
Autore/i: S. Corvaro; M. Miozzi; M. Postacchini; A. Mancinelli; M. Brocchini
Classificazione: 1 Contributo su Rivista
Abstract: We study the dynamics of the oscillatory bottom boundary layer (BBL) that develops at a porous bed under the action of propagating water waves (also known as “ventilated BBL”). In particular, experimental tests of a ventilated BBL generated over a permeable bed made of regular plastic spheres are analysed. With the purpose of characterizing typical dynamics of nearshore waves evolving over dissipative seabeds, we focus on one specific forcing condition, characterized by large nonlinearities and vorticity generation, and expect that such dynamics be qualitatively similar also for other wave regimes. Particle tracking enables an accurate definition of the hydrodynamics generated over the porous medium with specific focus on Eulerian velocity and vorticity fields and on Lagrangian particle trajectories. Nearbed velocity components are strongly influenced by the bed configuration (sphere caps) and are characterized by small-scale oscillations due to the presence of coherent structures over the interstices. Counter-rotating vortex sheets are generated and evolve during the entire wave period; their thickness grows rapidly when flow injection from the bed occurs, while it remains constant under the influence of in-bed flow suction. The evolution of near-bed particles is influenced by strain or vortex-dominated regions. When the intensity of the vortices just outside the BBL is large (generally after flow inversion), the momentum associated to the rotation of the lower layer of vortices in the BBL is comparable with that of the passive tracers, hence the particles are captured and their original trajectories are modified, jumping to a different layer. On the contrary when strain regions are dominant, particles are restricted in the same vorticity layer until sweep or ejection turbulent processes are observed and anomalous particle transport occurs from lower to higher vortex layers and vice versa. The latter occurs during the entire wave cycle, becoming the dominant process, while the former occurs before flow inversion and close to the porous bed. This result reveals that nearbed small-scale phenomena are weakly influenced by the wave mean flow. A detailed description of fluid suction and injection is proposed in terms of the mean flow dynamics (at wave scale), while the actual inflow/outflow of particles at the bed is seen to depend on local, small-scale flow properties. Suction and injection are generated during positive and negative water surface elevations and either squeeze or expand the flow downward/upward. The suction/injection perturbations contribute to the triggering of sweep and ejection events. Suction is mainly concentrated very close to the bed, injection is rapidly transported above the BBL, but the highest turbulence occurs in correspondence of suction events.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/184303 Collegamento a IRIS

2014
Sediment transport and morphodynamics generated by a dam-break swash uprush: Coupled vs uncoupled modeling
COASTAL ENGINEERING
Autore/i: Postacchini M.; Othman I.K.; Brocchini M.; Baldock T.E.
Classificazione: 1 Contributo su Rivista
Abstract: The present work analyzes the hydro-morphodynamics characterizing the swash region during the uprush stage. A comparison is illustrated between the sediment transport measured in a series of dam-break experiments and that predicted by the numerical hydro-morphodynamic model of Postacchini et al. (2012). The primary aim is to investigate the differences arising between the weakly coupled or uncoupled model and the measurements, in terms of hydrodynamics, tip celerity and sediment transport. The hydrodynamics are well described by the model and results have been used to calibrate both friction factor and subgrid turbulent viscosity. Comparison of numerically-computed tip celerity with experimental data reveals a fairly good agreement, i.e. a mean error of about 10%, while modeled sediment transport differs by about 40% from the available data. No evident differences are found between results obtained from the coupled and uncoupled model runs (2% for the celerity and 11% for the sediment transport rate at the tip), suggesting that for the specific flow under investigation, at the leading edge of the swash front, hydro-morphological coupling is not an issue of fundamental importance. However, for the special case here of a swash forced by a dam-break, scour occurs at the dam location, and in this case the erosion of the bed is significantly larger in the uncoupled model.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/188304 Collegamento a IRIS

2013
Fluid-particle interaction and generation of coherent structures over permeable beds: an experimental analysis
Proceedings of "Two-Phase Modelling for Sediment Dynamics In Geophysical Flows" - THESIS-2013 -S.H.F.
Autore/i: Postacchini M.; Corvaro S.; Miozzi M.; Mancinelli A.; Brocchini M.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/164730 Collegamento a IRIS

2013
A natural-scale analysis of estuarine cohesive sediments: the EscoSed project
8th international SedNet conference - Innovative sediment management: how to do more with less
Autore/i: Brocchini M.; Calantoni J.; Postacchini M.; Reed A.H.; Lorenzoni C.; Russo A.; Mancinelli A.; Corinaldesi V.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/164733 Collegamento a IRIS

2013
The hydro-morphodynamic response of a protected beach subject to sea storms: a numerical study
PROCEEDINGS OF THE 35TH IAHR WORLD CONGRESS, VOLS III AND IV
Autore/i: Postacchini, Matteo; Russo, Aniello; Sandro Carniel; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Sea storms are becoming more and more important in the economy of coastal areas, because they heavily affect both maintenance and life of the defense/touristic facilities, especially if they take place during the summer period. In conjunction with this, the design of traditional coastal defense structures is crucial for the protection of such facilities. The present study, based on numerical simulations performed by means of an innovative shallow-water numerical hydro-morphodynamic solver, explores the overall response of a protected beach to sea storms. Numerical tests have been run with the purpose of evaluating both i) the effect of real-life sea storms with different spectral characteristics, and ii) the influence of the positioning of shore-parallel submerged breakwaters on the beach morphology. The results of the simulations have revealed that erosion/accretion patterns depend weakly on the different sea storm conditions here used. On the other hand, the morphodynamics induced around the barriers is strongly influenced by the breakwater positioning: for the forcing here analyzed, the more the structures are offshore located, the more the bed variation is intense. On the opposite, the swash zone morphology is weakly influenced by the positioning of the breakwaters.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/247226 Collegamento a IRIS

2012
Un'analisi preliminare sul ruolo della vegetazione nell'idrodinamica dei canali a sezione composta
Atti del XXXIII Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: Soldini L.; Postacchini M.; Brocchini M.
Editore: EdiBios, Cosenza, Italia
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/80053 Collegamento a IRIS

2012
The morphological response of beaches protected by different breakwater configurations
Proc. 33rd Int. Conf. Coast. Engng-ASCE
Autore/i: C. Lorenzoni; M. Postacchini; A. Mancinelli; M. Brocchini
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/107265 Collegamento a IRIS

2012
A hydro-morphodynamic model for the nearshore region: Resolution of the exner equation
Proceedings of the International Offshore and Polar Engineering Conference
Autore/i: Postacchini M.; Brocchini M
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/174909 Collegamento a IRIS

2012
Small-scale dynamics and fluid-particle interaction around a cylinder placed over a porous seabed
50th European Two phase flow group meeting 2012
Autore/i: Mattioli M.; Postacchini M.; Corvaro S.; Mancinelli A.; Brocchini M.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/164739 Collegamento a IRIS

2012
A multi-purpose, intra-wave, shallow water hydro-morphodynamic solver
ADVANCES IN WATER RESOURCES
Autore/i: Postacchini, Matteo; Brocchini, Maurizio; Mancinelli, Alessandro; Landon, Marc
Classificazione: 1 Contributo su Rivista
Abstract: A hydro-morphodynamic numerical model is illustrated as a novel contribution to the investigation and prediction of nearshore and riverine flows and seabed changes forced by waves and currents. The model includes a robust hydrodynamic solver for the integration of the nonlinear shallow water equations (NSWE) and a rather flexible solver for the resolution of the Exner equation (used to evaluate the morphological evolution of the seabed). A detailed analysis is given of existing and novel procedures for the solution of the morphodynamic problem. Coupling of NSWE and Exner equations and updating of the solution is made by means of a sequential splitting scheme. The model has been validated by reproducing both analytical and numerical solutions, available in the recent literature, as well as an in-house laboratory experiment. The simulation of existing theoretical solutions has revealed the model performs well, especially in the prediction of the seabed evolution due to either bed-load or suspended-load transport forced by dam-break and swash-type events. The latter ones are seen to force both erosion and accretion despite the weak hydro-morphodynamic coupling. The comparison between solver results and experimental data is also encouraging, the solver reproducing well the main seabed features forced by irregular waves.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/64717 Collegamento a IRIS

2012
Bore-induced macrovortices over a planar beach: the cross-sea condition case
Proceedings of the 33rd International Conference on Coastal Engineering 2012
Autore/i: M. Postacchini; M. Brocchini; L. Soldini
Editore: ASCE-COPRI Coastal Engineering Research Council
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Wave breaking over submerged topographic obstacles leads to vorticity generation and, at times, to the generation of strong offshore-directed rip currents. The generation of finite-length breakers may also be induced by the positive interaction of wave trains propagating to shore with a relative angle. Such an interaction gives rise to a short-crested system, this, in turn, generating both breakers of finite crossflow length and an intense associated vorticity. We here analyze such a vorticity generation mechanism specifically focusing on the location where wave breaking occurs. To this purpose we both derive a simple theory, based on the well-known theory of wave ray propagation, and perform ad-hoc numerical simulations, using a NSWE (Nonlinear Shallow Water Equations) solver. A fairly good comparison between such preliminary theoretical and numerical results suggests that the present work be used as the basis for future analyses of vorticity generation by cross-seas.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/128723 Collegamento a IRIS

2011
Numerical Hydro-morphodinamic 2DH model for the shallow waters
Autore/i: Postacchini, Matteo
Editore: Università Politecnica delle Marche
Classificazione: 8 Tesi di dottorato
Abstract: Nella presente tesi viene descritto un solutore numerico idro-morfodinamico, quale contributo innovativo nello studio e previsione dei flussi sotto-costa e delle variazioni di fondale indotte da onde e correnti. Il modello include un robusto solutore idrodinamico per l'integrazione delle Non-Linear Shallow Water Equations (NSWE) ed un solutore piuttosto flessibile per la risoluzione dell'equazione di Exner (utilizzato per valutare l'evoluzione morfologica del fondale marino). L’accoppiamento delle NSWE con l’equazione di Exner e l'aggiornamento della soluzione vengono effettuati mediante uno schema di splitting sequenziale. Il modello è stato validato mediante la riproduzione sia di test numerici/analitici, presenti nella letteratura degli ultimi anni, sia delle esperienze di laboratorio eseguite nel Laboratorio di Idraulica dell’Università Politecnica delle Marche (AN). La simulazione delle soluzioni teoriche esistenti ha portato a risultati coerenti sia per quanto riguarda l'idrodinamica sia la morfodinamica, soprattutto nella previsione dell’evoluzione dei fondali marini dovuta al trasporto solido al fondo o a quello in sospensione, in seguito a eventi di dam-break e di swash. Il confronto tra risultati numerici del solutore e dati sperimentali è parzialmente soddisfacente. Infatti, il solutore riproduce abbastanza bene le caratteristiche principali del fondo in presenza di onde spettrali, ma fallisce quando vengono riprodotte onde regolari, a causa di “effetti di laboratorio”, verificatisi in canaletta.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/242267 Collegamento a IRIS

2011
Vortex generation in rigid-bed and mobile-bed compound channels
ATTI DEL XX CONGRESSO AIMETA DI MECCANICA TEORICA E APPLICATA
Autore/i: POSTACCHINI M.; BROCCHINI M.; MANCINELLI A.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: CD-ROM. In formato cartaceo solo i sommari
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/63790 Collegamento a IRIS

2011
Comparative analysis of sea wave dissipation induced by three flow mechanisms
JOURNAL OF HYDRAULIC RESEARCH
Autore/i: Postacchini M.; Brocchini M.; Corvaro S.; Lorenzoni C.; Mancinelli A.
Classificazione: 1 Contributo su Rivista
Abstract: A comparative analysis is performed on the wave energy dissipation efficiency on various coastal protection devices. In-house experimental data on the performance of two innovative coastal defence methods and of traditional submerged breakwaters have been used. The analysis provides a quantitative comparison of the efficiency of wave dissipators based on either wave-breaking turbulence, near-bed turbulence, or inside-seabed turbulence decay. The comparison is made on the basis of wave height decay patterns described as a function of suitable dimensionless parameters. The dimensionless volume of maximum turbulence decay is found to be a useful parameter for the analysis. Efficiencies in reducing the intensity of the incident waves are measured by the wave transmission coefficient, which is found to range between 0.4 and 1.0. Submerged breakwaters were found to be the most efficient wave dissipators, especially for large waves, while comparable efficiencies are provided by the three mechanisms under analysis if the flow is forced by moderate waves.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/57199 Collegamento a IRIS

2010
Esperimenti in larga scala sull'effetto del raggruppamento delle onde sulla morfodinamica della zona di battigia.
ATTI DEL XXXII CONVEGNO NAZIONALE DI IDRAULICA E COSTRUZIONI IDRAULICHE
Autore/i: Vicinanza D.; Contestabile P.; Postacchini M.; Brocchini M.
Editore: Walter Farina Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/59706 Collegamento a IRIS

2010
Some experimental results on the efficiency of different breakwater configuartions
ATTI DEL XXXII CONVEGNO NAZIONALE DI IDRAULICA E COSTRUZIONI IDRAULCIHE
Autore/i: POSTACCHINI M.; LORENZONI C.; MANCINELLI A.; BROCCHINI M.
Editore: Walter Farina Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/58299 Collegamento a IRIS

2010
Working of defence coastal structures dissipating by macro-roughness
JOURNAL OF WATERWAY PORT COASTAL AND OCEAN ENGINEERING-ASCE
Autore/i: Lorenzoni, Carlo; Soldini, Luciano; Brocchini, Maurizio; Mancinelli, Alessandro; Postacchini, Matteo; Seta, E; Corvaro, Sara
Editore: American Society of Civil Engineers / ASCE:1801 Alexander Bell Drive, # A776:Reston, VA 20191:(800)548-2723, (703)295-6210, EMAIL: marketing@asce.org, INTERNET: http://www.pubs.asce.org, Fax: (703)295-6211
Classificazione: 1 Contributo su Rivista
Abstract: The working features of innovative coastal defense structures that can dissipate the energy of incoming waves by the action of large-scale bottom unevennesses rigid blades covering the lower half of the water depth were investigated by means of a laboratory experimental campaign. The goal of the study was to characterize the ability of the structures to efficiently reduce the wave height with a minimal change in the mean water superelevations. Similar wave height reductions were achieved for both vertical and inclined blades; their efficiency was slightly superior to that of traditional submerged rubble-mound breakwaters of the same cross-shore extension. For the incident waves examined, very low mean water elevations were observed inshore of the structures, with the inclined blades producing the smallest values. These results suggest that the structures analyzed here could represent an alternative to submerged rubble-mound breakwaters from a hydrodynamic point of view to protect coastlines prone to erosion with minimal risk of dangerous rip currents.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/50310 Collegamento a IRIS

2009
Experimental tests on sandy beach model protected by low-crested structures
Proceedings of the 4th SCACR International Short Conference on Applied Coastal Research, IAHR
Autore/i: Lorenzoni C.; Mancinelli A.; Postacchini M.; Mattioli M.; Soldini L.; Corvaro S.
Editore: Nuova Bios
Luogo di pubblicazione: CASTROLIBERO (COSENZA)
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/65952 Collegamento a IRIS

2009
Some experimental studies on the sea wave disspation over different seabeds
AIMETA 2009 Atti del XIX Congresso dell'Associazione Italiana di Meccanica Teorica e Applicata
Autore/i: Corvaro, Sara; Lorenzoni, Carlo; Postacchini, Matteo; Seta, E; Soldini, Luciano; Brocchini, Maurizio; Mancinelli, Alessandro
Editore: Aras Edizioni
Luogo di pubblicazione: ANCONA
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/51350 Collegamento a IRIS

2009
An experimental analysis of the hydronamics of submerged structures dissipating by macro-roughness
Proceedings of the 2nd International Conference on the Application of Physical Modelling to Port and Coastal Protection - COASTLAB 08
Autore/i: C. LORENZONI; M. BROCCHINI; A. MANCINELLI; L. SOLDINI; E. SETA; M. POSTACCHINI
Editore: IAHR
Luogo di pubblicazione: MADRID
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/52314 Collegamento a IRIS

2009
Some experimental studies on the sea wave dissipation over different seabeds
Atti del XIX Congresso dell'Associazione di Meccanica Teorica e Applicata
Autore/i: Corvaro S.; Lorenzoni C.; Postacchini M.; Seta E.; Soldini L.; Brocchini M.; Mancinelli A.
Editore: Aras Edizioni
Luogo di pubblicazione: Ancona
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: CD_ROM, FL-02, Paper n.117
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/65951 Collegamento a IRIS

2009
Study of the wave damping due to a porous bed
Atti del 2nd International Conference on the Application of Physical Modeling to Port and Coastal Protection
Autore/i: Corvaro S.; Seta E.; Postacchini M.; Mancinelli A.; Lorenzoni C.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/65953 Collegamento a IRIS

2008
Prove sperimentali in canale per onde su fondo permeabile
Atti del XXXI Convegno Nazionale di Idraulica e Costruzioni Idrauliche
Autore/i: CORVARO S.; LORENZONI C.; MANCINELLI A.; POSTACCHINI M.; SETA E.
Editore: Morlacchi Editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: CD-ROM, Paper n.332
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/65954 Collegamento a IRIS

2008
Prove sperimentali in canale per onde di mare su fondo permeabile
Atti del 31° convegno nazionale di idraulica e costruzioni idrauliche, CD-ROM allegato,332.pdf
Autore/i: S. CORVARO; C. LORENZONI; A. MANCINELLI; M. POSTACCHINI; E. SETA
Editore: Morlacchi editore
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/48423 Collegamento a IRIS

2008
Hydrodynamic laboratory tests on a dissipative submerged structure for beach protection
Proceedings of the 5th International Conference on Marine Waste Water Discharges and Coastal Environment MWWD 2008, CD-ROM
Autore/i: LORENZONI C; MANCINELLI A; POSTACCHINI M; SETA E; L. SOLDINI; ZANELLA M
Editore: MWWD Organization
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: (CD-Rom, pp. 13)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/53130 Collegamento a IRIS




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