30 pubblicazioni classificate nel seguente modo:

Cardiac and vascular modeling in sport
The Bioengineering of sport
Autore/i: Zitti, Gianluca; Mousavi, SEYYED MAHMOUD; Brocchini, Maurizio; Pedrizzetti, Gianni
Editore: Pàtron editore
Luogo di pubblicazione: Bologna
Classificazione: 2 Contributo in Volume
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/325294

Particle dynamics due to interaction between a breaking-induced vortex and a nearbed vortex
PHYSICS OF FLUIDS
Autore/i: Brocchini, Maurizio; Marini, Francesco; Falchi, Massimo; Postacchini, Matteo; Zitti, Gianluca
Classificazione: 1 Contributo su Rivista
Abstract: A single regular wave, travelling over a submerged abrupt discontinuity, is able to generate a pair of counter-rotating vortices. A nearbed vortex is generated by the flow separation that occurs at the bed, while a surface vortex can be generated by either a direct (co-rotating vortex) or a backward (counter-rotating vortex) breaking. Starting from recent laboratory test results, which showed the influence of the wave nonlinearity on the interaction between the counter-rotating vortices and led to the identification of three different regimes, the present work illustrates the main findings obtained from the optical analysis of the flow field induced by three waves, each belonging to a specific nonlinear regime. Specifically, for each test, synthetic particles have been seeded within the domain, with the aim to obtain long-lasting trajectories driven by the Eulerian flow field obtained through the Particle Tracking Velocimetry (PTV) analysis, to be studied by means of single-particle and multi-particle statistics. Both absolute and relative statistics confirm that a ballistic regime exist just after the particle release at each location of the domain. At larger times, the absolute statistics suggest a subdiffusive regime both within the vortices and between such areas (in correspondence of the breaking-induced jet), followed by a superdiffusive regime, dominated by rotation and particle release. Differently, the relative diffusivity suggests the occurrence of a superdiffusive regime at t>TL, corresponding to enstrophy cascade and exponential growth, followed by a Richardson regime and then by an oscillatory behavior, during which particles are periodically trapped and released by vortices.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/309956

Dynamics of a pile-moored fish cages in current and waves: A numerical study
OCEAN ENGINEERING
Autore/i: Zitti, G.; Novelli, N.; Brocchini, M.
Classificazione: 1 Contributo su Rivista
Abstract: We propose a numerical study of the dynamics of a double-constrained cylindrical pile-moored fish-farm cage, to be possibly installed at the foundations of dismissed offshore structures. Our model, derived from the net-truss model of Kristiansen and Faltinsen (2012), takes into account the elasticity of the net material, the real size of the net and is applied with and without mesh-grouping approaches, this allowing us to evaluate the range of validity of mesh-grouping techniques. First, cage dynamics have been studied with small-scale tests, in which the numerical model accurately reproduces the behaviour of the cage in both sea currents (velocity in the range 0.5−1m/s) and waves of small amplitude (with height of 1 m and period in the range 4−32 s). Use of the net real size for the computation grid of small-scale tests allows for identification of the main phenomena influencing the load distribution and the volume loss, which are: the dominant sail-shape deformation in the streamwise direction, the flattened deformations in the cross flow direction, and high-frequency oscillations in the vertical direction in long waves. Subsequently, a prototype-scale test is run to simulate the dynamics of a realistic installation of a double-constrained cylindrical pile-moored fish-farm cage in the Adriatic sea (considering both 1m/s sea current and storm sea state characterized by a peak period Tp=4 s and significant wave height Hs=1.5 m), showing that the major loads are a compression load on the pile up to 1 kN and a bending moment at the pile base up to 9.1 kNm. The proposed configuration always showed a small net relative volume loss VL<5%.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/309955

Numerical evaluation of the action on a pile-moored fish cage forced by a storm sea state in different configurations
Proceedings of the 39th IAHR World Congress
Autore/i: Zitti, Gianluca; Novelli, Nico; Brocchini, Maurizio
Editore: International association of hydro-environment engineering and research
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: The conservation and reuse of the foundation of offshore platforms, at times, can be more ecologically sustainable than their complete removal, which can result in the loss of biodiversity. In our work we consider fish-farming as possible reuse of offshore depleted oil and gas mono-pile infrastructures, being the role of aquaculture in fish-food supply continuously increasing in the last decades. Offshore fish-farm cages are exposed to strong actions and knowing the dynamical response of the cage to different marine forcing is fundamental for the design of the structure. Hence, the dynamics of cylindrical pile-moored fish cages has been studied numerically with a net-truss model, including the screen model for the viscous forces proposed by Kristiansen and Faltinsen (2012) and the elasticity of the net trusses (Zitti et al.,2020, 2022). The model simulates a cylindrical cage fixed to a top ring and a bottom ring, which are moored to the central tubular pillar, whose net is characterized by solidity ratio Sn=0.087, material density pnet=1140 kg/m3, and Young modulus E =81Ί06 N/m2. The grouping method with G=10 is included in the model, for the reduction of the computational cost of the simulations. The cage net is forced with a flow derived by a linear superposition of the flows associated to linear waves, based on a JONSWAP spectrum representative a storm sea state typical of the Adriatic sea, on the Italian East coast, where a number of mono-pile oil and gas infrastructures are located. Different configurations of the cage are simulated and the resulting actions on the support system are compared.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/308027

Fluid-Structure Interaction of a Partially Submerged Body: an Analytical Model for the Human Stability in Floodwaters
Proceedings of the 39th IAHR World Congress
Autore/i: Postacchini, Matteo; Zitti, Gianluca
Editore: International association of hydro-environment engineering and research
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: Climate change is increasing the number of extreme events, like floods or long-lasting rainfalls, in densely inhabited area, this focusing the attention on the safety of human being in flooded urban areas. The stability of people subjected to floodwaters is an important aspect to evaluate people’s safety. To this aim, many theoretical and experimental works analyze human stability using simplified and conservative approaches, although the role of body articulation and posture on human stability in floodwaters is relevant. We here propose simple analytical models to evaluate the effect of flood impact on a human body with different postures, composed by a two-dimensional frame of three beams, which represent different parts of the human body with variable orientation. The body stability is described by means of a dynamic equilibrium of the system, which accounts for a tilting moment generated by the toppling mechanism induced by floodwater conditions, and a resisting moment that changes with the body posture and the inertial characteristics of each beam. The model results are compared with recent laboratory experiments, where a human body at a quasi-natural scale was reproduced and subjected to several floodwater scenarios. Results show how the posture of the human body can provide a significant contribution to the stabilizing moment in the case of backward toppling.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/308105

Interaction between breaking-induced vortices and near-bed structures. Part 1. Experimental and theoretical investigation
JOURNAL OF FLUID MECHANICS
Autore/i: Brocchini, M.; Marini, F.; Postacchini, M.; Zitti, G.; Falchi, M.; Xie, Z.
Classificazione: 1 Contributo su Rivista
Abstract: The present work describes the vortex-vortex interactions observed during laboratory experiments, where a single regular water wave is allowed to travel over a discontinuous rigid bed promoting the generation of both near-bed and surface vortices. While near-bed vortices are generated by the flow separation occurring at the bed discontinuity, surface vortices are induced by the wave breaking in conjunction with a breaking-induced jet. A 'backward breaking' (previously observed in the case of solitary waves) occurs at the air-water interface downstream of the discontinuity and generates a surface anticlockwise vortex that interacts with the near-bed clockwise vortex. With the vortex-vortex interaction influenced by many physical mechanisms, a point-vortex model, by which vortices evolve under both self-advection (in relation to both free surface and seabed) and mutual interaction, has been implemented to separately investigate the vortex- and wave-induced dynamics. The available data indicate that both self-advection and mutual interaction are the governing mechanisms for the downward motion of the surface vortex, with the effect of the breaking-induced jet being negligible. The same two mechanisms, combined with the mean flow, are responsible for the almost horizontal and oscillating path of the near-bed vortex. The investigation of the vortex paths allow us to group the performed tests into three distinct classes, each characterized by a specific range of wave nonlinearity. The time evolution of the main variables characterizing the vortices (e.g. circulation, kinetic energy, enstrophy, radius) and their maximum values increase with the wave nonlinearity, such dependences being described by synthetic best-fit formulas.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/302022

Numerical simulation of coronary arteries blood flow: effects of the aortic valve and boundary conditions
Theoretical and Applied Mechanics - AIMETA 2022
Autore/i: Mousavi, S. M.; Zitti, G.; Pozzi, M.; Brocchini, M.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/313928

Interaction between wave breaking-induced vortices and nearbed structures: preliminary numerical results and laboratory-test design
Atti del 37° Convegno Nazionale di Idraulica e Costruzioni Idrauliche. Ingegneria delle acque: cambiamenti globali e sostenibilità.
Autore/i: Brocchini, M.; Marini, F.; Postacchini, M.; Zitti, G.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/299200

Initial investigation of athletes’ electrocardiograms acquired by wearable sensors during the pre-exercise phase
THE OPEN BIOMEDICAL ENGINEERING JOURNAL
Autore/i: Romagnoli, S.; Sbrollini, A.; Colaneri, M.; Marcantoni, I.; Morettini, M.; Zitti, G.; Brocchini, M.; Pozzi, M.; Burattini, L.
Classificazione: 1 Contributo su Rivista
Abstract: Aim: The aim of this study is to support large-scale prevention programs fighting sport-related sudden cardiac death by providing a set of electrocardiographic features representing a starting point in the development of normal reference values for the pre-exercise phase. Background: In people with underlying, often unknown, cardiovascular abnormalities, increased cardiovascular load during exercise can trigger sport-related sudden cardiac death. Prevention remains the only weapon to contrast sport-related sudden cardiac death. So far, no reference values have been proposed for electrocardiograms of athletes acquired with wearable sensors in the pre-exercise phase, consisting of the few minutes immediately before the beginning of the training session. Objective: To perform an initial investigation of athletes’ electrocardiograms acquired by wearable sensors during the pre-exercise phase. Methods: The analyzed electrocardiograms, acquired through BioHarness 3.0 by Zephyr, belong to 51 athletes (Sport Database and Cycling Database of the Cardiovascular Bioengineering Lab of the Università Politecnica delle Marche, Italy). Preliminary values consist of interquartile ranges of six electrocardiographic features which are heart rate, heart-rate variability, QRS duration, ST level, QT interval, and corrected QT interval. Results: For athletes 35 years old or younger, preliminary values were [72;91]bpm, [26;47]ms, [85;104]ms, [-0.08;0.08]mm, [326;364]ms and [378;422]ms, respectively. For athletes older than 35 years old, preliminary values were [71;94]bpm, [16;65]ms, [85;100]ms, [-0.11;0.07]mm, [330;368]ms and [394;414]ms, respectively. Conclusion: Availability of preliminary reference values could help identify those athletes who, due to electrocardiographic features out of normal ranges, are more likely to develop cardiac complications that may lead to sport-related sudden cardiac death.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/291630

Preliminary results on the dynamics of a pile-moored fish cage with elastic net in currents and waves
JOURNAL OF MARINE SCIENCE AND ENGINEERING
Autore/i: Zitti, G.; Novelli, N.; Brocchini, M.
Classificazione: 1 Contributo su Rivista
Abstract: Over the last decades, the aquaculture sector increased significantly and constantly, mov-ing fish-farm plants further from the coast, and exposing them to increasingly high forces due to currents and waves. The performances of cages in currents and waves have been widely studied in literature, by means of laboratory experiments and numerical models, but virtually all the research is focused on the global performances of the system, i.e., on the maximum displacement, the volume reduction or the mooring tension. In this work we propose a numerical model, derived from the net-truss model of Kristiansen and Faltinsen (2012), to study the dynamics of fish farm cages in current and waves. In this model the net is modeled with straight trusses connecting nodes, where the mass of the net is concentrated at the nodes. The deformation of the net is evaluated solving the equation of motion of the nodes, subjected to gravity, buoyancy, lift, and drag forces. With respect to the original model, the elasticity of the net is included. In this work the real size of the net is used for the computation mesh grid, this allowing the numerical model to reproduce the exact dynamics of the cage. The numerical model is used to simulate a cage with fixed rings, based on the concept of mooring the cage to the foundation of no longer functioning offshore structures. The defor-mations of the system subjected to currents and waves are studied.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/287981

A Preliminary Validation of a New Surgical Procedure for the Treatment of Primary Bladder Neck Obstruction Using a Computational Modeling Approach
BIOENGINEERING
Autore/i: Serpilli, Michele; Zitti, Gianluca; Dellabella, Marco; Castellani, Daniele; Maranesi, Elvira; Morettini, Micaela; Lenci, Stefano; Burattini, Laura
Classificazione: 1 Contributo su Rivista
Abstract: A new surgical procedure for the treatment of primary bladder neck obstruction with maintenance of anterograde ejaculation is proposed. In place of monolateral or bilateral bladder neck incision, associated with a loss of ejaculation rate of up to 30%, the new surgical procedure consists of laser drilling the bladder neck with a number of holes and without muscle fiber disrup- tion. The effect of this novel procedure has been studied numerically, with a simplified two-dimen- sional numerical model of the internal urethral sphincter, varying the position and the number of holes in the fibrotic region of the urethral tissue. Results show an improvement of the urethral sphincter opening by increasing the number of holes, ranging from about 6% to 16% of recovery. Moreover, a non-aligned position of holes positively influences the opening recovery. The concen- trations of maximum principal strain and stress have been registered in the proximity of the inter- face between the physiologic and diseased sphincter, and in those regions where the radial thick- ness is significantly thinner. The effects on the first five patients have been included in the study, showing improvement in micturition, lower urinary tract symptoms, sustained ejaculatory func- tion, and quality of life.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/290912

Fluid dynamics in the functional foregut of xylem-sap feeding insects: A comparative study of two Xylella fastidiosa vectors
JOURNAL OF INSECT PHYSIOLOGY
Autore/i: Ranieri, E.; Zitti, G.; Riolo, P.; Isidoro, N.; Ruschioni, S.; Brocchini, M.; Almeida, R. P. P.
Classificazione: 1 Contributo su Rivista
Abstract: Xylem sap sucking insects are adapted to ingest fluids under tension. Although much has been learned about such feeding strategy, this adaptation still poses several unresolved questions, including how these insects ingest against strong xylem sap tension. Xylem sap-feeding insects are vectors of the plant pathogenic xylem-limited bacterium Xylella fastidiosa. This bacterium colonizes the cuticular lining of the foregut of vectors in a persistent manner. We used micro-computed tomography and scanning electron microscopy to investigate the foregut morphometry of two X. fastidiosa vector species: Philaenus spumarius and Graphocephala atropunctata (Hemiptera: Aphrophoridae and Cicadellidae, respectively). On the basis of morphometric data, we built a hydrodynamic model of the foregut of these two insect species, focusing on the precibarium, a region previously shown to be colonized by X. fastidiosa and correlated with pathogen acquisition from and inoculation to plants. Our data show that space in the P. spumarius functional foregut could potentially harbor twice as many cells as similar space in G. atropunctata, although the opposite trend has been observed with biological samples. Average flow velocity of ingested fluid depended on the percentage of the cibarium volume exploited for suction: if the entire volume were used, velocities were in the range of meters per second. In contrast, velocities on the order of those found in the literature (about 10 cm/s) were attained if only 5% of the cibarium volume were exploited. Simulated bacterial colonization of the foregut was analyzed in relation to hydrodynamics and pressure needed for insects to ingest. Our model is designed to represent the diameter reduction of the food canal in both insect species when infected with X. fastidiosa. Results indicated that full bacterial colonization significantly increased the mean sap-sucking flow velocity. In particular, the colonization increased the maximum section-averaged velocity in the G. atropunctata more than two times and the net pressure needed to mantain the flow in the precibarium when colonized is relevant (about 0.151 MPa) if compared to a standard xylem sap tension (1 MPa). Bacterial colonization also influenced the sucking process of the G. atropunctata, by hindering the formation of a recirculation zone (or eddy), that characterizd the flow in the distal part of the precibarium when bacteria were absent. On the other hand, considering the pressure the insect must generate to feed, X. fastidiosa colonization probably influences fitness of the G. atropunctata more than that of P. spumarius.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273201

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

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

Efficiency evaluation of a ductless Archimedes turbine: Laboratory experiments and numerical simulations
RENEWABLE ENERGY
Autore/i: Zitti, G.; Fattore, F.; Brunori, A.; Brunori, B.; Brocchini, M.
Classificazione: 1 Contributo su Rivista
Abstract: The aim of designing a new hydrokinetic turbine simple, cheap, environmentally friendly and suitable for installation in remote areas is pursued by studying the efficiency of an Archimedes turbine that exploits the kinetic energy of a water stream rather than an upstream-downstream difference in water head. First, the efficiency of a hydrokinetic Archimedes turbine has been studied using laboratory experiments for low TSR regimes. Subsequently, numerical simulations have been run to evaluate the performance coefficient of the turbine only (without frictional losses or blockage augmentation), and to extend the TSR range. Numerical simulations have allowed to produce the efficiency curve of the hydrokinetic Archimedes turbine in both aligned and inclined configurations. The obtained maximum performance coefficients have been compared with those of other hydrokinetic turbines currently in use and inspected through a parametric analysis dedicated to explore the practical applications of the proposed turbine.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/273202

Numerical investigation on the effects of the pitch angle on the efficiency of an Archimedean-type turbine
proceeding of the 13th European Wave and Tidal Energy Conference (EWTEC 2019)
Autore/i: Zitti, Gianluca; Fattore, F.; Brunori, A.; Brunori, B.; Brocchini, Maurizio
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292652

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

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

Monitoring for Coastal Resilience: Preliminary Data from Five Italian Sandy Beaches
SENSORS
Autore/i: Parlagreco, Luca; Melito, Lorenzo; Devoti, Saverio; Perugini, Eleonora; Soldini, Luciano; Zitti, Gianluca; Brocchini, Maurizio
Classificazione: 1 Contributo su Rivista
Abstract: Video-monitoring can be exploited as a valuable tool to acquire continuous, high-quality information on the evolution of beach morphology at a low cost and, on such basis, perform beach resilience analyses. This manuscript presents preliminary results of an ongoing, long-term monitoring programme of five sandy Italian beaches along the Adriatic and Tyrrhenian sea. The project aims at analyzing nearshore morphologic variabilities on a time period of several years, to link them to resilience indicators. The observations indicate that most of the beach width variations can be linked to discrete variations of sandbar systems, and most of all to an offshore migration and decay of the outermost bars. Further, the largest net shoreline displacements across the observation period are experienced by beaches with a clear NOM (Net Offshore Migration)-type evolution of the seabed.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/265226

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

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

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

EFFICIENCY EVALUATION OF AN ARCHIMEDEAN-TYPE HYDROKINETIC TURBINE IN A STEADY CURRENT
proceeding of the 13th International Conference on Hydrodynamics
Autore/i: Zitti, Gianluca; Brocchini, Maurizio; Fattore, F.; Brunori, A.; Brunori, B.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/292654

Experimental Setup for the Validation of the Bio-Inspired Thruster of an Ostraciiform Swimming Robot
2018 14th IEEE/ASME International Conference on Mechatronic and Embedded Systems and Applications, MESA 2018
Autore/i: Costa, D.; Callegari, M.; Palmieri, G.; Scaradozzi, D.; Brocchini, M.; Zitti, G.
Editore: Institute of Electrical and Electronics Engineers Inc.
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Abstract: In the last two decades, bio-inspired solutions have been thoroughly investigated as a source of efficiency and manoeuvrability improvement for underwater robots. The possibility to design a machine capable of propelling itself like a marine animal strongly depends on the understanding of the mechanics principles underlying biological swimming. The adoption of advanced simulation and measurement techniques is then fundamental to investigate the fluid-structure interaction phenomena characterizing the locomotion of aquatic animals. To address this very ambitious objective, the Authors designed an experimental setup devised to investigate the propulsive performances of an ostraciiform swimming robot. The numerical simulations performed on an oscillating foil led to the design of a dedicated force sensor, able to allow a complete characterization of the bio-inspired thruster and its actuation mechanism. The experimental test campaign is still under development but the results of the preliminary tests are hereby provided
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/261561

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

Avalanche-induced impact water waves
Autore/i: Zitti, Gianluca
Editore: Università Politecnica delle Marche
Classificazione: 8 Tesi di dottorato
Abstract: Questa tesi propone un primo studio, mediante un modello bidimensionale semplificato, della generazione di tsunami in bacini d’acqua a causa dell’impatto di valanghe di neve. Uno studio analitico è stato effettuato mediante l’applicazione delle equazioni di bilancio ad un volume di controllo che include la zona di impatto della valanga e di formazione dell’onda. Le equazioni ottenute evidenziano quali sono i parametri fisici coinvolti nel problema. Inoltre, riscrivendo l’equazione di bilancio in termini di moto del baricentro della massa solida sommersa, si ottiene l’equazione di un oscillatore armonico. Lo studio mediate approccio grafico mostra una forma della soluzione simile al caso a coefficienti costanti, confrontabile con i dati sperimentali ed utilizzabile per la determinazione di funzioni predittive del moto della massa solida dopo l’impatto. Lo studio sperimentale è stato condotto mediante prove in canaletta variando le caratteristiche adimensionali della slavina che influenzano la formazione dell’onda e rilevando l’elevazione della superficie libera e il moto della massa solida impattata. Le caratteristiche dell’onda generata e del moto della massa impattata sono state confrontate, mediante regressioni non lineari (NLR), alle caratteristiche della slavina, arrivando a definire due coefficienti che mostrano eccellenti capacità previsionali delle caratteristiche dell’onda generata in prossimità dell’impatto. Il moto del baricentro della massa sommersa può essere efficacemente approssimato con le equazioni del moto dell’oscillatore armonico smorzato a coefficienti costanti. Mediante NLR, i coefficienti di tali equazioni sono stati scritti in termini dei coefficienti predittivi della slavina. Infine, lo studio delle caratteristiche dell’onda nello spazio suggerisce la presenza di una zona in prossimità dell’impatto in cui il comportamento dell’onda è fortemente non lineare, ma le sue caratteristiche posso essere valutate mediante le relazioni fornite.
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/242980

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, Gianluca; Ancey, C.; Postacchini, Matteo; Brocchini, Maurizio
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

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

Rate-independent deformation patterning in crystal plasticity
Vols 651-653
Autore/i: Lancioni, Giovanni; Zitti, Gianluca; Yalcinkaya, Tuncay
Classificazione: 4 Contributo in Atti di Convegno (Proceeding)
Scheda della pubblicazione: https://iris.univpm.it/handle/11566/229789

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