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1
Takagi, Emiko, Yasuhiko Saito e Angelique W. M. Chan. "A Longitudinal Study of the Impact of Loneliness on Personal Mastery Among Older Adults in Singapore". Innovation in Aging 4, Supplement_1 (1 dicembre 2020): 318. http://dx.doi.org/10.1093/geroni/igaa057.1017.
Testo completoAbstract (sommario):
Abstract This study uses longitudinal data to examine the association between older adults’ sense of mastery and loneliness. We examined the data of a nationally representative sample of adults 60 years and older in Singapore (Wave1, n=4,990) from the Panel of Health and Aging among Older Singaporeans Survey. The initial participants were followed up in 2011 (Wave2, n=3,103) and in 2015 (Wave3, n=1,572). At each wave, emotional loneliness was assessed using the UCLA three-item loneliness scale and sense of mastery was measured with the five items from the Pearlin Mastery Scale. We conducted cross-lagged regression analyses where loneliness and personal mastery scores in each wave were treated as endogenous variables along with covariates including demographic characteristics, health conditions, and the overall strength of social network measured by Lubben Social Network Scale. The results showed that loneliness in wave 1 and wave 2 respectively predicted a lower level of personal sense of mastery in subsequent waves. However, the other direction, the influence of personal mastery in wave 1 and wave 2 on loneliness at subsequent waves, was not significant. Furthermore, the analysis showed that older adults’ relatively strong social network was related to a lower level of loneliness and a higher sense of mastery at Wave 3. The finding suggests that loneliness plays a critical role in influencing older adults’ personal sense of mastery and that the strength of social network is an important mediator of loneliness and personal sense of mastery amongst older adults and a potential area for intervention.
2
Verao Fernandez, Gael, Vasiliki Stratigaki, Panagiotis Vasarmidis, Philip Balitsky e Peter Troch. "Wake Effect Assessment in Long- and Short-Crested Seas of Heaving-Point Absorber and Oscillating Wave Surge WEC Arrays". Water 11, n. 6 (29 maggio 2019): 1126. http://dx.doi.org/10.3390/w11061126.
Testo completoAbstract (sommario):
In the recent years, the potential impact of wave energy converter (WEC) arrays on the surrounding wave field has been studied using both phase-averaging and phase-resolving wave propagation models. Obtaining understanding of this impact is important because it may affect other users in the sea or on the coastline. However, in these models a parametrization of the WEC power absorption is often adopted. This may lead to an overestimation or underestimation of the overall WEC array power absorption, and thus to an unrealistic estimation of the potential WEC array impact. WEC array power absorption is a result of energy extraction from the incoming waves, and thus wave height decrease is generally observed downwave at large distances (the so-called “wake” or “far-field” effects). Moreover, the power absorption depends on the mutual interactions between the WECs of an array (the so-called “near field” effects). To deal with the limitations posed by wave propagation models, coupled models of recent years, which are nesting wave-structure interaction solvers into wave propagation models, have been used. Wave-structure interaction solvers can generally provide detailed hydrodynamic information around the WECs and a more realistic representation of wave power absorption. Coupled models have shown a lower WEC array impact in terms of wake effects compared to wave propagation models. However, all studies to date in which coupled models are employed have been performed using idealized long-crested waves. Ocean waves propagate with a certain directional spreading that affects the redistribution of wave energy in the lee of WEC arrays, and thus gaining insight wake effect for irregular short-crested sea states is crucial. In our research, a new methodology is introduced for the assessment of WEC array wake effects for realistic sea states. A coupled model is developed between the wave-structure interaction solver NEMOH and the wave propagation model MILDwave. A parametric study is performed showing a comparison between WEC array wake effects for regular, long-crested irregular, and short-crested irregular waves. For this investigation, a nine heaving-point absorber array is used for which the wave height reduction is found to be up to 8% lower at 1.0 km downwave the WEC array when changing from long-crested to short-crested irregular waves. Also, an oscillating wave surge WEC array is simulated and the overestimation of the wake effects in this case is up to 5%. These differences in wake effects between different wave types indicates the need to consider short-crested irregular waves to avoid overestimating the WEC array potential impacts. The MILDwave-NEMOH coupled model has proven to be a reliable numerical tool, with an efficient computational effort for simulating the wake effects of two different WEC arrays under the action of a range of different sea states.
3
Grilli, Stephan T., Jeffrey C. Harris, Fengyan Shi, James T. Kirby, Tayebeh S. Tajalli Bakhsh, Elise Estibals e Babak Tehranirad. "NUMERICAL MODELING OF COASTAL TSUNAMI IMPACT DISSIPATION AND IMPACT". Coastal Engineering Proceedings 1, n. 33 (15 dicembre 2012): 9. http://dx.doi.org/10.9753/icce.v33.currents.9.
Testo completoAbstract (sommario):
Recent observations of the coastal impact of large tsunamis (e.g., Indian Ocean 2004; Tohoku 2011) and related numerical and theoretical works have made it increasingly clear that tsunami waves arrive nearshore as a series of long waves (so-called N-waves) with, often, the superposition of undular bores around each crest. Such wave trains are much more complex and very much in contrast with the solitary wave paradigm which for a long time was the accepted idealization of tsunami waves in both experimental and numerical work. The dissipation associated with these breaking bores can be very large, particularly over a wide and shallow continental shelf such as along the east coast of North America, particularly for the shorter waves associated with tsunamis generated by Submarine Mass Failures (SMFs). In this paper, we perform numerical simulations of tsunami coastal impact in the context of both idealized laboratory experiments and several tsunami case studies. We attempt to clarify the key physical processes at play in such cases, and discuss the parameterization of long wave dissipation and implications for models of coastal tsunami hazard assessment.
4
Li, Zhisong, Kirti Ghia, Ye Li, Zhun Fan e Lian Shen. "Unsteady Reynolds-averaged Navier–Stokes investigation of free surface wave impact on tidal turbine wake". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 477, n. 2246 (febbraio 2021): 20200703. http://dx.doi.org/10.1098/rspa.2020.0703.
Testo completoAbstract (sommario):
Tidal current is a promising renewable energy source. Previous studies have investigated the influence of surface waves on tidal turbines in many aspects. However, the turbine wake development in a surface wave environment, which is crucial for power extraction in a turbine array, remains elusive. In this study, we focus on the wake evolution behind a single turbine and its interaction with surface waves. A numerical solver is developed to study the effects of surface waves on an industrial-size turbine. A case without surface wave and two cases with waves and different rotor depths are investigated. We obtain three-dimensional flow field descriptions near the free surface, around the rotor, and in the near- and far-wake. In a comparative analysis, the time-averaged and instantaneous flow fields are examined for various flow characteristics, including momentum restoration, power output, free surface elevation and vorticity dynamics. A model reduction technique is employed to identify the coherent flow structures and investigate the spatial and temporal characteristics of the wave–wake interactions. The results indicate the effect of surface waves in augmenting wake restoration and reveal the interactions between the surface waves and the wake structure, through a series of dynamic processes and the Kelvin–Helmholtz instability.
5
Gonzalez-Santamaria, Raul, Qingping Zou, Shunqi Pan e Roberto Padilla-Hernandez. "MODELLING WAVE-TIDE INTERACTIONS AT A WAVE FARM". Coastal Engineering Proceedings 1, n. 32 (27 gennaio 2011): 34. http://dx.doi.org/10.9753/icce.v32.waves.34.
Testo completoAbstract (sommario):
The Wave Hub project will create the world’s largest wave farm off the coast of Cornwall, Southwest England. This study is to investigate wave and tide interactions, in particular their effects on bottom friction and sediment transport at the wave-farm coast. This is an ambitious project research which includes the use of a very complex numerical modelling system. The main question to answer is how waves, tidal currents and winds affect the bottom friction at the Wave Hub site and the near-shore zone, as well as their impact on the sediment transport. Results show that tidal elevation and tidal currents have a significant effect on the wave height predictions, tidal forcing and wind waves have a significant effect on the bed shear-stress, relevant to sediment transport, waves via radiation stresses have an important effect on the long-shore and cross-shore velocity components, particularly during the spring tides, waves can impact on bottom boundary layer and the mixing in the water column. Interactions between waves and tides at the Wave Hub site is important when modelling coastal morphology influenced by wave energy devices, this open-source modelling system tool will help the study of physical impacts on the Wave Hub farm area.
6
Kerpen, Nils, Talia Schoonees e Torsten Schlurmann. "Wave Impact Pressures on Stepped Revetments". Journal of Marine Science and Engineering 6, n. 4 (13 dicembre 2018): 156. http://dx.doi.org/10.3390/jmse6040156.
Testo completoAbstract (sommario):
The wave impacts on horizontal and vertical step fronts of stepped revetments is investigated by means of hydraulic model tests conducted with wave spectra in a wave flume. Wave impacts on revetments with relative step heights of 0.3 < Hm0/Sh < 3.5 and a constant slope of 1:2 are analyzed with respect to (1) the probability distribution of the impacts, (2) the time evolution of impacts including a classification of load cases, and (3) a special distribution of the position of the maximum impact. The validity of the approved log-normal probability distribution for the largest wave impacts is experimentally verified for stepped revetments. The wave impact properties for stepped revetments are compared with those of vertical seawalls, showing that their impact rising times are within the same range. The impact duration for stepped revetments is shorter and decreases with increasing step height. Maximum horizontal wave impact loads are about two times larger than the corresponding maximum vertical wave impact loads. Horizontal and vertical impact loads increase with a decreasing step height. Data are compared with findings from literature for stepped revetments and vertical walls. A prediction formula is provided to calculate the maximum horizontal wave impact at stepped revetments along its vertical axis.
7
Rodriguez Gandara, Ruben, e John Harris. "NEARSHORE WAVE DAMPING DUE TO THE EFFECT ON WINDS IN RESPONSE TO OFFSHORE WIND FARMS". Coastal Engineering Proceedings 1, n. 33 (25 ottobre 2012): 55. http://dx.doi.org/10.9753/icce.v33.waves.55.
Testo completoAbstract (sommario):
Despite the progress that has been made in modeling wind wake interaction between turbines in offshore wind farms, only a handful of studies have quantified the impact of wind turbines or wave farms upon surface waves, and there are even less articles about the wave blockage induced by the whole array of turbines upon wind waves. This hypothetical case study proposes a methodology that takes into account the combined effect of wind wake and wave blockage on wind waves when transforming offshore waves to nearshore in an offshore wind farm scenario.
8
Shimura, Tomoya, Nobuhito Mori, Tomohiro Yasuda e Hajime Mase. "WAVE DYNAMICS AND ITS IMPACT TO WAVE CLIMATE PROJECTION". Coastal Engineering Proceedings 1, n. 33 (25 ottobre 2012): 24. http://dx.doi.org/10.9753/icce.v33.management.24.
Testo completoAbstract (sommario):
Impacts and adaptations of climate change have been studied in various fields. In order to assess the impacts of climate change on coastal areas, it is necessary to evaluate how wave change due to climate changes. Projections of global wave climate have been carried out by some research groups for next IPCC report. Projection of wave climate contains uncertainties, such as scenario uncertainty, GCM uncertainty and wave model uncertainty. Impacts and adaptations of climate change have been studied in various fields. In order to assess the impacts of climate change on coastal areas, it is necessary to evaluate how wave change due to the climate changes. Projections of global wave climate have been carried out by some research groups for next IPCC report. Projection of wave climate contains uncertainties, such as scenario uncertainty, GCM uncertainty and wave model uncertainty. The uncertainties need to be estimated for reliable projections. In this study, wave model uncertainty was evaluated. Global wave hindcasts were conducted using SWAN with four different models of source terms and the impacts of different wave models on global long-term wave statistics were made clear. Furthermore, the global characteristics of differences in long-term wave statistics due to different models were compared with the result of global wave climate projection (Mori et al., 2010). Global long-term wave statistics are varied depending on choice of formula of Sin and Swc rather than that of Snl4. The uncertainty is larger in eastern lower latitude of ocean especially in the Pacific where swells dominate. On the other hand, the uncertainty of future wave climate change due to wave model is negligibly small in higher latitude where wind-waves dominate.
9
Mu, Ping, Pingyi Wang, Linfeng Han, Meili Wang, Caixia Meng, Zhiyou Cheng e Haiyong Xu. "The Propagation of Landslide-Generated Impulse Waves and Their Impacts on the Moored Ships: An Experimental Investigation". Advances in Civil Engineering 2020 (12 maggio 2020): 1–13. http://dx.doi.org/10.1155/2020/6396379.
Testo completoAbstract (sommario):
The effective prevention and reduction of the hazardous impact of landslide-generated impulse waves on the moored ships are crucial for the sustainable operation of the reservoirs. Although the investigations of landslide-generated impulse waves have been widely studied in the past decades, few efforts involved their impacts on the moored ships. The authors in this paper specifically examine the hazardous impact of the impulse waves on the moored ships by applying the physical experiments. Considering that the impulse wave was an external force acting on the mooring line, the impulse wave generation, propagation, and its impact on the moored ships are hence explored in detail. The results indicate that the impact of impulse waves on the moored ships was mainly due to the first wave amplitude and height, and an exponential function relationship between the relative wave height and wave crest amplitude was revealed. Furthermore, the attenuation of the maximum wave crest amplitude was approximated by a power exponential function. On this basis, the mooring tension could be calculated based on the linear relationship between the mooring tension and wave height. Ultimately, the safety of the moored ships in the port can be evaluated.
10
Lindt, John W. van de, Rakesh Gupta, Daniel T. Cox e Jebediah S. Wilson. "Wave Impact Study on a Residential Building". Journal of Disaster Research 4, n. 6 (1 dicembre 2009): 419–26. http://dx.doi.org/10.20965/jdr.2009.p0419.
Testo completoAbstract (sommario):
Recent natural disasters around the world including both tsunamis and hurricanes, have highlighted the inability of wood buildings to withstand wave and surge loading during these extreme events. Little is known about the interaction between coastal residential light-frame wood buildings and wave and surge loading because often little is left of the buildings. This leaves minimal opportunity for forensic investigations. This paper summarizes the results of a study whose objective was to begin to better understand the interaction between North American style residential structures and wave loading. To do this, one-sixth scale residential building models typical of North American coastal construction, were subjected to tsunami wave bores generated from waves of heights varying from 10 cm to 60 cm. The lateral force produced by the wave bores were, as expected, found to vary nonlinearly with parent wave height.
11
Lavroff, J., M. R. Davis, D. S. Holloway, G. A. Thomas e J. J. McVicar. "Wave impact loads on wave-piercing catamarans". Ocean Engineering 131 (febbraio 2017): 263–71. http://dx.doi.org/10.1016/j.oceaneng.2016.11.015.
Testo completo
12
Didenkulova, I., e A. Rodin. "A typical wave wake from high-speed vessels: its group structure and run-up". Nonlinear Processes in Geophysics 20, n. 1 (26 febbraio 2013): 179–88. http://dx.doi.org/10.5194/npg-20-179-2013.
Testo completoAbstract (sommario):
Abstract. High-amplitude water waves induced by high-speed vessels are regularly observed in Tallinn Bay, the Baltic Sea, causing intense beach erosion and disturbing marine habitants in the coastal zone. Such a strong impact on the coast may be a result of a certain group structure of the wave wake. In order to understand it, here we present an experimental study of the group structure of these wakes at Pikakari beach, Tallinn Bay. The most energetic vessel waves at this location (100 m from the coast at the water depth 2.7 m) have amplitudes of about 1 m and periods of 8–10 s and cause maximum run-up heights on a beach up to 1.4 m. These waves represent frequency modulated packets where the largest and longest waves propagate ahead of other smaller amplitude and period waves. Sometimes the groups of different heights and periods can be separated even within one wave wake event. The wave heights within a wake are well described by the Weibull distribution, which has different parameters for wakes from different vessels. Wave run-up heights can also be described by Weibull distribution and its parameters can be connected to the parameters of the distribution of wave heights 100 m from the coast. Finally, the run-up of individual waves within a packet is studied. It is shown that the specific structure of frequency modulated wave packets, induced by high-speed vessels, leads to a sequence of high wave run-ups at the coast, even when the original wave heights are rather moderate. This feature can be a key to understanding the significant impact on coasts caused by fast vessels.
13
Wu, Lichuan, David Sproson, Erik Sahlée e Anna Rutgersson. "Surface Wave Impact When Simulating Midlatitude Storm Development". Journal of Atmospheric and Oceanic Technology 34, n. 1 (gennaio 2017): 233–48. http://dx.doi.org/10.1175/jtech-d-16-0070.1.
Testo completoAbstract (sommario):
AbstractSurface gravity waves, present at the air–sea interface, can affect the momentum flux and heat fluxes by modifying turbulence in the lower layers of the atmosphere. How to incorporate wave impacts into model parameterizations is still an open issue. In this study, the influence of a dynamic roughness length (considering instantaneous wave-induced stress), horizontal resolution, and the coupling time resolution between waves and the atmosphere on storm simulations are investigated using sensitivity experiments. Based on the simulations of six midlatitude storms using both an atmosphere–wave coupled model and an atmospheric stand-alone model, the impacts are investigated. Adding the wave-induced stress weakens the storm intensity. Applying a roughness length tuned to an average friction velocity is not enough to capture the simulation results from “true” wave-related roughness length. High-horizontal-resolution models intensify the simulation of storms, which is valid for both coupled and uncoupled models. Compared with the atmospheric stand-alone model, the coupled model (considering the influence of dynamic roughness length) is more sensitive to the model horizontal resolution. During reasonable ranges, the coupling time resolution does not have a significant impact on the storm intensity based on the limited experiments used in this study. It is concluded that the dynamic wave influence (instantaneous wave influence) and the model resolution should be taken into account during the development of forecast and climate models.
14
Kida, S., e H. Kakishima. "IMPACT WAVE AND STRESS". Experimental Techniques 16, n. 2 (marzo 1992): 32–35. http://dx.doi.org/10.1111/j.1747-1567.1992.tb01254.x.
Testo completo
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Wünnemann, K., e R. Weiss. "The meteorite impact-induced tsunami hazard". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 373, n. 2053 (28 ottobre 2015): 20140381. http://dx.doi.org/10.1098/rsta.2014.0381.
Testo completoAbstract (sommario):
When a cosmic object strikes the Earth, it most probably falls into an ocean. Depending on the impact energy and the depth of the ocean, a large amount of water is displaced, forming a temporary crater in the water column. Large tsunami-like waves originate from the collapse of the cavity in the water and the ejecta splash. Because of the far-reaching destructive consequences of such waves, an oceanic impact has been suggested to be more severe than a similar-sized impact on land; in other words, oceanic impacts may punch over their weight. This review paper summarizes the process of impact-induced wave generation and subsequent propagation, whether the wave characteristic differs from tsunamis generated by other classical mechanisms, and what methods have been applied to quantify the consequences of an oceanic impact. Finally, the impact-induced tsunami hazard will be evaluated by means of the Eltanin impact event.
16
Jiang, Qingfang, e Shouping Wang. "Impact of Gravity Waves on Marine Stratocumulus Variability". Journal of the Atmospheric Sciences 69, n. 12 (1 dicembre 2012): 3633–51. http://dx.doi.org/10.1175/jas-d-12-0135.1.
Testo completoAbstract (sommario):
Abstract The impact of gravity waves on marine stratocumulus is investigated using a large-eddy simulation model initialized with sounding profiles composited from the Variability of American Monsoon Systems (VAMOS) Ocean–Cloud–Atmosphere–Land Study Regional Experiment (VOCALS-Rex) aircraft measurements and forced by convergence or divergence that mimics mesoscale diurnal, semidiurnal, and quarter-diurnal waves. These simulations suggest that wave-induced vertical motion can dramatically modify the cloud albedo and morphology through nonlinear cloud–aerosol–precipitation–circulation–turbulence feedback. In general, wave-induced ascent tends to increase the liquid water path (LWP) and the cloud albedo. With a proper aerosol number concentration, the increase in the LWP leads to enhanced precipitation, which triggers or strengthens mesoscale circulations in the boundary layer and accelerates cloud cellularization. Precipitation also tends to create a decoupling structure by weakening the turbulence in the subcloud layer. Wave-induced descent decreases the cloud albedo by dissipating clouds and forcing a transition from overcast to scattered clouds or from closed to open cells. The overall effect of gravity waves on the cloud variability and morphology depends on the cloud property, aerosol concentration, and wave characteristics. In several simulations, a transition from closed to open cells occurs under the influence of gravity waves, implying that some of the pockets of clouds (POCs) observed over open oceans may be related to gravity wave activities.
17
Schellin, Thomas E., e Ould el Moctar. "Numerical Prediction of Impact-Related Wave Loads on Ships". Journal of Offshore Mechanics and Arctic Engineering 129, n. 1 (8 novembre 2006): 39–47. http://dx.doi.org/10.1115/1.2429695.
Testo completoAbstract (sommario):
We present a numerical procedure to predict impact-related wave-induced (slamming) loads on ships. The procedure was applied to predict slamming loads on two ships that feature a flared bow with a pronounced bulb, hull shapes typical of modern offshore supply vessels. The procedure used a chain of seakeeping codes. First, a linear Green function panel code computed ship responses in unit amplitude regular waves. Ship speed, wave frequency, and wave heading were systematically varied to cover all possible combinations likely to cause slamming. Regular design waves were selected on the basis of maximum magnitudes of relative normal velocity between ship critical areas and wave, averaged over the critical areas. Second, a nonlinear strip theory seakeeping code determined ship motions under design wave conditions, thereby accounting for the nonlinear pressure distribution up to the wave contour and the frequency dependence of the radiation forces (memory effect). Third, these nonlinearly computed ship motions constituted part of the input for a Reynolds-averaged Navier–Stokes equations code that was used to obtain slamming loads. Favorable comparison with available model test data validated the procedure and demonstrated its capability to predict slamming loads suitable for design of ship structures.
18
Buravova, S. N., I. S. Gordopolova e E. V. Petrov. "FEATURES STRAIN LOCALISATION UNDER IMPACT LOADS". IZVESTIA VOLGOGRAD STATE TECHNICAL UNIVERSITY, n. 11(246) (26 novembre 2020): 64–68. http://dx.doi.org/10.35211/1990-5297-2020-11-246-64-68.
Testo completoAbstract (sommario):
The localization of plastic strain under impulse loads is determined by the sample geometry and is practically independent on the material properties. Deformation bands are a consequence of ultrasonic oscillations, which occurs when waves are reflected (compression and unloading) on the sample faces, and when the reflected waves interact with each other, and flows in the form of standing waves. Localized strain bands originate and develop at the nodes of standing waves under conditions of alternating deformation and are accompanied by mass transfer of particles from the matrix material (interstitial and substitutional atoms, impurity atoms, ultrafine particles of the hardening phase) to the sites of spall damage. The absence of energy transfer through the nodal points of the standing wave increases the duration of the sample deformation after the passage of the shock wave.
19
LIU, ZHANFANG, XIAOYONG SUN e YUAN GUO. "ON ELASTIC STRESS WAVES IN AN IMPACTED PLATE". International Journal of Applied Mechanics 06, n. 04 (9 luglio 2014): 1450047. http://dx.doi.org/10.1142/s1758825114500471.
Testo completoAbstract (sommario):
Elastic stress wave theory is developed and the stress waves in the impacted plate are examined in the paper. Generalized linear elasticity is adopted where the couple stress and curvature tensor are both deviatoric tensors and they meet a linear constitutive relation. It is found that there exist volumetric, rotational, and deviatoric waves in the generalized elastic solids. However, for macro-scale elastic solids only two wave modes, namely a volumetric wave and a deviatoric wave should be taken into account. Wave motion in plate impact tests is studied that a volumetric wave and a deviatoric wave are proposed. A set of exact solutions is attained for elastic stress waves in an impact plate. Excitation of stress waves at impact surface and reflection at free surface are formulated. Propagation of stress waves in the plate is analyzed in the waveforms. The predicted stress history in a ceramic plate under impact is agreed very well with the experiment measurement.
20
Aartsen, M. W. "MODEL STUDY ON THE IMPACT OF WAVES". Coastal Engineering Proceedings 1, n. 6 (29 gennaio 2011): 45. http://dx.doi.org/10.9753/icce.v6.45.
Testo completoAbstract (sommario):
The problem to be investigated is the structural strength of a sluice gate under the influence of wave attack. The gate was designed in view of the hydraulic forces in quasi permanent conditions The fact, however, that the gate is exposed to wave attack, necessitates an investigation of:
1) the transient forces due to impact,
2) the possibilities of modificating the shape of the gate in order to avoid, or at least to diminish, the chance on the occurrence of impacts.
As the mechanism of wave attack is influenced by the hydrodynamic properties of the oncoming waves, the tests are being carried out in a flume in which the waves are generated by wind in order to simulate the expected extreme natural conditions as close as possible.
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Freeman, Elizabeth, Kristen Splinter e Ron Cox. "FLOATING BREAKWATERS AS PUBLIC PLATFORMS – IMPACT ON POSTURAL STABILITY". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 63. http://dx.doi.org/10.9753/icce.v36.structures.63.
Testo completoAbstract (sommario):
Floating Breakwaters are used extensively to provide cost effective protection from wind and vessel waves. Floating breakwaters are commonly multitasked, being used as a point of mooring for vessels or simply an access way to other pontoons in a small boat harbour, as well as their main function as wave dissipators. A floating breakwater does not completely stop the incident wave; rather it partially transmits, partially reflects and partially dissipates the wave energy. Cox et al (2007) completed wave flume testing of a number of floating breakwaters and reported on performance in irregular waves with particular emphasis on wave transmission and reflection, energy dissipation and restraining forces. Motion measurements were limited by the instrumentation. This paper discusses the results from a further series of laboratory experiments on the dynamic motions of an active floating breakwater system. The performance is related to wave attenuation, wave reflection and energy dissipation as well as safety considerations for standing persons based on high resolution measurements of accelerations in all six degrees of freedom.
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Moideen, Rameeza, Manasa Ranjan Behera, Arun Kamath e Hans Bihs. "NUMERICAL MODELLING OF SOLITARY AND FOCUSED WAVE FORCES ON COASTAL-BRIDGE DECK". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 12. http://dx.doi.org/10.9753/icce.v36.structures.12.
Testo completoAbstract (sommario):
In the recent past, coastal bridges have been subjected to critical damage due to extreme wave attacks during natural calamities like storm surge and tsunami. Various numerical and experimental studies have suggested different empirical equations for wave impact on deck. However, they do not account the velocities of the wave type properly, which requires a detailed investigation to study the impact of extreme waves on decks. Solitary wave assumption is more suitable for shallow water waves, while the focused wave has been used widely to represent extreme waves. The present study aims to investigate the focused wave impact on coastal bridge deck using REEF3D (Bihs et al., 2016).
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Radecki, Rafal, Wieslaw Jerzy Staszewski e Tadeusz Uhl. "Impact of Changing Temperature on Lamb Wave Propagation for Damage Detection". Key Engineering Materials 588 (ottobre 2013): 140–48. http://dx.doi.org/10.4028/www.scientific.net/kem.588.140.
Testo completoAbstract (sommario):
Lamb waves are the most widely used guided ultrasonic waves for structural damage detection. One of the major problems associate with Lamb wave propagation is the effect of temperature on wave propagation parameters. It is important that these parameters are more sensitive to damage than to varying temperature. The paper demonstrates how amplitude and arrival time of Lamb waves are affected by temperature. The analysis is performed for the experimental data gathered from Lamb wave propagation in a damaged aluminium plate. A simple clustering algorithm is used to distinguish between "undamaged" and "damaged" conditions in the presence of changing temperature.
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Dao, M. H., H. Xu, E. S. Chan e P. Tkalich. "Modelling of tsunami wave run-up, breaking and impact on vertical wall by SPH method". Natural Hazards and Earth System Sciences Discussions 1, n. 3 (22 giugno 2013): 2831–57. http://dx.doi.org/10.5194/nhessd-1-2831-2013.
Testo completoAbstract (sommario):
Abstract. Accurate predictions of wave run-up and run-down are important for coastal impact assessment of relatively long waves such as tsunami or storm waves. Wave run-up is, however, a complex process involving nonlinear build-up of the wave front, intensive wave breaking and strong turbulent flow, making the numerical approximation challenging. Recent advanced modeling methodologies could help to overcome these numerical challenges. For a demonstration, we study run-up of non-breaking and breaking solitary waves on vertical wall using two methods, the enhanced Smoothed Particle Hydrodynamics (SPH) method and the traditional non-breaking nonlinear model Tunami-N2. The Tunami-N2 model fails to capture the evolution of steep waves at the proximity of breaking that observed in the experiments. Whereas, the SPH method successfully simulate the wave propagation, breaking, impact on structure and the reform and breaking processes of wave run-down. The study also indicates that inadequate approximation of the wave breaking could lead to significant under-predictions of wave height and impact pressure on structures. The SPH model shows potential applications for accurate impact assessments of wave run-up onto coastal structures.
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Butt, Hafiz Sana Ullah, e Pu Xue. "Wave Dispersion and Attenuation in Viscoelastic Split Hopkinson Pressure Bar". Key Engineering Materials 535-536 (gennaio 2013): 547–50. http://dx.doi.org/10.4028/www.scientific.net/kem.535-536.547.
Testo completoAbstract (sommario):
The Split Hopkinson Pressure Bar (SHPB) is most commonly used facility to obtain material properties at high strain rates. Testing of soft materials using this method requires that bars made of low impedance material should be used, in order to improve signal-to-noise ratio of transmitted stress. However, utilization of such bars poses some difficulties in data processing as the wave dispersion and attenuation becomes noticeable due to their viscoelastic nature. Wave propagation coefficients of a viscoelastic pressure bar are evaluated using incident and reflected strain waves generated through impact of two different length striker bars. Two approaches are proposed for propagation coefficient measurement in this study, namely direct and waves-overlap. Using two approaches, it is found that the calculated attenuation coefficients are same, while the wave numbers are different. The difference in wave number in the case of two approaches is due to the difference in calculated phase change of incident and reflected waves, which is found as integer multiple of 2Π. Moreover, propagation coefficients calculated through different striker impacts are found different. The propagation coefficient found through long striker impact, when used for propagation response prediction of waves generated by short striker impact, resulted in high oscillations in predicted waves.
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Rivolo, Simone, Lucas Hadjilucas, Matthew Sinclair, Pepijn van Horssen, Jeroen van den Wijngaard, Roman Wesolowski, Amedeo Chiribiri, Maria Siebes, Nicolas P. Smith e Jack Lee. "Impact of coronary bifurcation morphology on wave propagation". American Journal of Physiology-Heart and Circulatory Physiology 311, n. 4 (1 ottobre 2016): H855—H870. http://dx.doi.org/10.1152/ajpheart.00130.2016.
Testo completoAbstract (sommario):
The branching pattern of the coronary vasculature is a key determinant of its function and plays a crucial role in shaping the pressure and velocity wave forms measured for clinical diagnosis. However, although multiple scaling laws have been proposed to characterize the branching pattern, the implications they have on wave propagation remain unassessed to date. To bridge this gap, we have developed a new theoretical framework by combining the mathematical formulation of scaling laws with the wave propagation theory in the pulsatile flow regime. This framework was then validated in multiple species using high-resolution cryomicrotome images of porcine, canine, and human coronary networks. Results demonstrate that the forward well-matchedness (no reflection for pressure/flow waves traveling from the coronary stem toward the microcirculation) is a salient feature in the coronary vasculature, and this result remains robust under many scenarios of the underlying pulse wave speed distribution assumed in the network. This result also implies a significant damping of the backward traveling waves, especially for smaller vessels (radius, <0.3 mm). Furthermore, the theoretical prediction of increasing area ratios (ratio between the area of the mother and daughter vessels) in more symmetric bifurcations found in the distal circulation was confirmed by experimental measurements. No differences were observed by clustering the vessel segments in terms of transmurality (from epicardium to endocardium) or perfusion territories (left anterior descending, left circumflex, and right coronary artery).
27
Dao, M. H., H. Xu, E. S. Chan e P. Tkalich. "Modelling of tsunami-like wave run-up, breaking and impact on a vertical wall by SPH method". Natural Hazards and Earth System Sciences 13, n. 12 (23 dicembre 2013): 3457–67. http://dx.doi.org/10.5194/nhess-13-3457-2013.
Testo completoAbstract (sommario):
Abstract. Accurate predictions of wave run-up and run-down are important for coastal impact assessment of relatively long waves such as tsunami or storm waves. Wave run-up is, however, a complex process involving nonlinear build-up of the wave front, intensive wave breaking and strong turbulent flow, making the numerical approximation challenging. Recent advanced modelling methodologies could help to overcome these numerical challenges. For a demonstration, we study run-up of non-breaking and breaking solitary waves on a vertical wall using two methods, an enhanced smoothed particle hydrodynamics (SPH) method and the traditional non-breaking nonlinear model Tunami-N2. The Tunami-N2 model fails to capture the evolution of steep waves at the proximity of breaking that was observed in the experiments. Whereas the SPH method successfully simulates the wave propagation, breaking, impact on structure and the reform and breaking processes of wave run-down. The study also indicates that inadequate approximation of the wave breaking could lead to significant under-predictions of wave height and impact pressure on structures. The SPH model shows potential applications for accurate impact assessments of wave run-up on to coastal structures.
28
Sharova, Vera, Igor Kantarzhi e Tran Long Giang. "Impact Wave on Port Mole in during Construction". Applied Mechanics and Materials 725-726 (gennaio 2015): 299–305. http://dx.doi.org/10.4028/www.scientific.net/amm.725-726.299.
Testo completoAbstract (sommario):
During construction of port breakwater, especially if it is built from the sea, waves interact with the walls, having different finite lengths [3]. In this paper, tasks, connected with definition of wave loads on structure and scour near the structure on walls of finite length, are considered. To study these processes the special experiments have been carried [3, 8]. It were measured the wave loads on the walls of finite length and it was studied the formation of scour near the structure. A comparison was made of the experimental data with the existing analytical solutions and with experiments.
29
Duchemin, L., e N. Vandenberghe. "Impact dynamics for a floating elastic membrane". Journal of Fluid Mechanics 756 (3 settembre 2014): 544–54. http://dx.doi.org/10.1017/jfm.2014.471.
Testo completoAbstract (sommario):
AbstractWe study impacts of a rigid body on a thin elastic sheet floating on a liquid. When struck by a solid object of small size, the elastic sheet deforms and waves propagate in and on the membrane. The impact triggers a longitudinal elastic wave effectively stretching the membrane. The hydroelastic transverse wave that propagates in the stretched domain is similar to capillary waves on a free surface with an equivalent ‘surface tension’ that results from the stretching of the elastic membrane. Two limiting cases, for which a self-similar solution can be computed, corresponding to short and long times are identified. Surprisingly, our study reveals that the fluid–body system behaves as a regular liquid–gas interface, but with an effective surface tension coefficient that scales linearly with the impact velocity.
30
Gruwez, Vincent, Ine Vandebeek, Dogan Kisacik, Maximilian Streicher, Corrado Altomare, Tomohiro Suzuki, Toon Verwaest, Andreas Kortenhaus e Peter Troch. "2D OVERTOPPING AND IMPACT EXPERIMENTS IN SHALLOW FORESHORE CONDITIONS". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 67. http://dx.doi.org/10.9753/icce.v36.papers.67.
Testo completoAbstract (sommario):
This paper introduces the 2D experiments conducted for the CREST project in the wave flume of Ghent University. The experiments focus on wave interactions with low-crested sea dikes fronted by a shallow foreshore and mildly to steeply sloping beaches, which is a very typical situation along the Belgian coast. Foreshore slopes of 1/20, 1/35, 1/50 and 1/80 were tested for a range of low to high energy wave conditions, a variation in wave steepness and two water levels. The main goal was to obtain a dataset in which the effects of the infragravity waves on the wave-structure interactions (i.e. wave overtopping and impact forces) can be studied. The tests included high spatial resolution surface elevation measurement tests, which is new for beaches including a dike in the inner surf zone. From the first results it became clear that the foreshore slope influences the wave transformation up to the dike toe. The influence is apparent comparing to existing (semi-) empirical models for prediction of the spectral wave period at the dike toe and wave overtopping at the dike crest. The high spatial resolution data show a steep increase in infragravity significant wave height in the very shallow area in front of the dike.
31
KIM, Y. E., M. RABINOWITZ, Y. K. BAE, G. S. CHULICK e R. A. RICE. "CLUSTER–IMPACT NUCLEAR FUSION: SHOCK–WAVE STATISTICAL ANALYSIS". Modern Physics Letters B 05, n. 14n15 (giugno 1991): 941–59. http://dx.doi.org/10.1142/s0217984991001179.
Testo completoAbstract (sommario):
Cluster–impact nuclear fusion is analyzed via a shock–wave model. We show that shock waves can be generated by clusters. Energy loss mechanisms are considered, and the conditions when they are not negligible are determined. Our theoretical model indicates that shock–wave enhanced fusion temperatures are possible with molecular size clusters impacting upon hydrogen isotope targets, somewhat as envisioned by Winterberg and Harrison for macro–projectiles. Our theory explains and reproduces the yields from known target and cluster compositions, as a function of cluster size and energy. Predictions are made, and new tests proposed. We show that contaminants are an unlikely artifact in the experimental data.
32
Peregrine, D. H. "WATER-WAVE IMPACT ON WALLS". Annual Review of Fluid Mechanics 35, n. 1 (gennaio 2003): 23–43. http://dx.doi.org/10.1146/annurev.fluid.35.101101.161153.
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Doyle, J. F. "IMPACT AND LONGITUDINAL WAVE PROPAGATION". Experimental Techniques 12, n. 1 (gennaio 1988): 29–31. http://dx.doi.org/10.1111/j.1747-1567.1988.tb02091.x.
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34
Baarholm, Rolf, e Odd M. Faltinsen. "Wave impact underneath horizontal decks". Journal of Marine Science and Technology 9, n. 1 (1 maggio 2004): 1–13. http://dx.doi.org/10.1007/s00773-003-0164-4.
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35
Zhao, Enjin, Ke Qu, Lin Mu, Simon Kraatz e Bing Shi. "Numerical Study on the Hydrodynamic Characteristics of Submarine Pipelines under the Impact of Real-World Tsunami-Like Waves". Water 11, n. 2 (29 gennaio 2019): 221. http://dx.doi.org/10.3390/w11020221.
Testo completoAbstract (sommario):
Submarine pipelines have been extensively used for marine oil and gas extraction due to their high efficiency, safety, and low price. However, submarine pipelines are vulnerable to extreme waves (i.e., tsunami waves). Previous research has often used solitary waves as a basis for studying the impacts of tsunami waves on submarine pipelines, although the hydrodynamic characteristics and wave properties drastically differ from those of real-world tsunami waves. This paper numerically investigates the hydrodynamic characteristics of tsunami waves interacting with submarine pipelines, but instead uses an improved wave model to generate a tsunami-like wave that more closely resembles those encountered in the real-world. The tsunami-like wave generated based on a real-world tsunami wave profile recorded during a 2011 tsunami in Japan has been applied. Given the same wave height, simulation results show that peak hydrodynamic forces of the tsunami-like wave are greater than those of the solitary wave. Meanwhile, the duration of the acting force under the tsunami-like wave is much longer than that of the solitary wave. These findings underline the basic reasons for the destructive power of tsunamis. It is also noted that the hydrodynamic forces of the pipeline under the tsunami-like wave increase with wave height, but will decrease as water depth increases. In addition to the single pipeline, the complicated hydrodynamic characteristics of pipelines in tandem arrangement have been also numerically studied. It is believed that the findings drawn from this paper can enhance our understanding of the induced forces on submarine pipelines under extreme tsunami waves.
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McNatt, J. Cameron, Aaron Porter, Christopher Chartrand e Jesse Roberts. "The Performance of a Spectral Wave Model at Predicting Wave Farm Impacts". Energies 13, n. 21 (2 novembre 2020): 5728. http://dx.doi.org/10.3390/en13215728.
Testo completoAbstract (sommario):
For renewable ocean wave energy to support global energy demands, wave energy converters (WECs) will likely be deployed in large numbers (farms), which will necessarily change the nearshore environment. Wave farm induced changes can be both helpful (e.g., beneficial habitat and coastal protection) and potentially harmful (e.g., degraded habitat, recreational, and commercial use) to existing users of the coastal environment. It is essential to estimate this impact through modeling prior to the development of a farm, and to that end, many researchers have used spectral wave models, such as Simulating WAves Nearshore (SWAN), to assess wave farm impacts. However, the validity of the approaches used within SWAN have not been thoroughly verified or validated. Herein, a version of SWAN, called Sandia National Laboratories (SNL)-SWAN, which has a specialized WEC implementation, is verified by comparing its wave field outputs to those of linear wave interaction theory (LWIT), where LWIT is theoretically more appropriate for modeling wave-body interactions and wave field effects. The focus is on medium-sized arrays of 27 WECs, wave periods, and directional spreading representative of likely conditions, as well as the impact on the nearshore. A quantitative metric, the Mean Squared Skill Score, is used. Results show that the performance of SNL-SWAN as compared to LWIT is “Good” to “Excellent”.
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Hansen, P. Friis. "On Combination of Slamming-and Wave-Induced Responses". Journal of Ship Research 38, n. 02 (1 giugno 1994): 104–14. http://dx.doi.org/10.5957/jsr.1994.38.2.104.
Testo completoAbstract (sommario):
Attempts to solve the combination problem of the low-frequency wave-induced bending and the high frequency slamming induced bending moments in ships have so far been based on a Poisson pulse train model for the occurrence of the slamming impacts. Embedded in the Poisson pulse model is the assumption that the time of occurrence and the intensity of a slamming impact are independent of the corresponding quantities of the previous impact. This assumption is not valid because the periodic character of the ship motion tends to concentrate the slamming impacts in clusters. Further, the times of occurrence of the slamming impact and the wave-induced stress peaks are highly correlated. Slamming impact usually generates the first peak of a compressive (sagging) slamming stress in the deck, as the wave-induced stress passes from hogging to sagging. The magnitude of the wave-induced and slamming-induced stress peaks, however, tends to be slightly negatively correlated. The work in the present paper is based on the so-called Slepian model process. This is a non-Gaussian and nonstationary process that gives a complete description of the original ergodic Gaussian process after an arbitrary upcrossing into a critical interval. By use of the Slepian model process, the joint distribution of the wave amplitude and the frequency is established at the occurrence of maximum slamming response within a cluster of slamming impacts. Thereafter the response is calculated for regular sinusoidal waves at selected wave amplitudes and frequencies. Response statistics are obtained by weighing the calculated response by the probability densities of the various pairs of wave amplitude and frequency.
38
Danial, A. N., e J. F. Doyle. "Transverse Impact of a Damped Plate near a Straight Edge". Journal of Vibration and Acoustics 117, n. 1 (1 gennaio 1995): 103–8. http://dx.doi.org/10.1115/1.2873852.
Testo completoAbstract (sommario):
The effects of boundaries on flexural wave propagation in plates with viscous damping are studied through spectral and finite element analyses of incident and reflected waves. The incident wave is generated by point impact and therefore has the complication of being circularly crested. Results show excellent agreement between finite element and spectral solutions for waves—with high and low damping—reflected from simply supported, clamped and free edges. In addition, the possibility of Rayleigh-type free edge waves are investigated.
39
Carballo, R., e G. Iglesias. "Wave farm impact based on realistic wave-WEC interaction". Energy 51 (marzo 2013): 216–29. http://dx.doi.org/10.1016/j.energy.2012.12.040.
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Hu, Xiaozhou, Yiyao Jiang e Daojun Cai. "Numerical Modeling and Simulation of Wave Impact of a Circular Cylinder during the Submergence Process". Modelling and Simulation in Engineering 2017 (2017): 1–14. http://dx.doi.org/10.1155/2017/2197150.
Testo completoAbstract (sommario):
Wave slamming loads on a circular cylinder during water entry and the subsequence submergence process are predicted based on a numerical wave load model. The wave impact problems are analyzed by solving Reynolds-Averaged Navier-Stokes (RANS) equations and VOF equations. A finite volume approach (FV) is employed to implement the discretization of the RANS equations. A two-dimensional numerical wave tank is established to simulate regular ocean waves. The wave slamming problems are investigated by deploying a circular cylinder into waves with a constant vertical velocity. The present numerical method is validated using other numerical or theoretical results in accordance with varying free surface profiles when a circular cylinder sinks in calm water. A numerical example is given to show the submergence process of the circular cylinder in waves, and both free surface profiles and the pressure distributions on the cylinder of different time instants are obtained. Time histories of hydrodynamic load on the cylinder during the submergence process for different wave impact angles, wave heights, and wave periods are obtained, and results are analyzed in detail.
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Stokes, Christopher, e Daniel Conley. "Modelling Offshore Wave farms for Coastal Process Impact Assessment: Waves, Beach Morphology, and Water Users". Energies 11, n. 10 (21 settembre 2018): 2517. http://dx.doi.org/10.3390/en11102517.
Testo completoAbstract (sommario):
The emerging global wave energy industry has the potential to contribute to the world’s energy needs, but careful consideration of potential impacts to coastal processes in the form of an impact assessment is required for each new wave energy site. Methods for conducting a coastal processes impact assessment for wave energy arrays vary considerably in the scientific literature, particularly with respect to characterising the energy absorption of a wave energy converter (WEC) array in a wave model. In this paper, modelling methods used in the scientific literature to study wave farm impacts on coastal processes are reviewed, with the aim of determining modelling guidance for impact assessments. Effects on wave climate, beach morphology, and the surfing resource for coastal water users are considered. A novel parameterisation for the WEC array transmission coefficient is presented that, for the first time, uses the permitted power rating of the wave farm, which is usually well defined at the impact assessment stage, to estimate the maximum likely absorption of a permitted WEC array. A coastal processes impact assessment case study from a wave farm in south-west Ireland is used to illustrate the application of the reviewed methods, and demonstrates that using the new ‘rated power transmission coefficient’ rather than a WEC-derived transmission coefficient or complete energy absorption scenario can make the difference between significant and non-significant levels of coastal impacts being predicted.
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KIDA, SOTO AKI, KEITA FUKUSHIMA e MASAYA MATSUMOTO. "THE REDUCTION OF STRESS WAVE PROPAGATION THROUGH POROUS MATERIALS". International Journal of Modern Physics B 22, n. 09n11 (30 aprile 2008): 1215–20. http://dx.doi.org/10.1142/s0217979208046566.
Testo completoAbstract (sommario):
Impact stress wave propagating through porous materials is investigated in order to examine the ability of the shock absorbing effect. The specimens are modeled as the porous medium with different porous diameters made of the acrylic resin plate. When these models are impacted with different impact velocities, the impact stress waves propagating before and after the porous parts are measured using the strain gages in the experiments. As the reduction effect of the impact stress wave propagating in the porous medium, we pay attention to the maximum stresses and the duration times from the histories of the impact stress waves. One-dimensional wave theory and dynamic element method simulated this model are applied in order to explain these phenomena.
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Hasbrouck, W. P. "Four shallow‐depth, shear‐wave feasibility studies". GEOPHYSICS 56, n. 11 (novembre 1991): 1875–85. http://dx.doi.org/10.1190/1.1442999.
Testo completoAbstract (sommario):
Studies using a hammer‐impact source were made to evaluate the feasibility of using shallow‐depth, seismic shear‐wave methods to (1) detect earth fissures, (2) map an aguiclude, (3) locate a bedrock channel, and (4) study the fault and fracture system within a highly fractured welded tuff. For detecting earth fissures, a V/V (vertical‐impact, vertical‐geophone—recording both P-waves and vertically polarized shear waves, SV), 6-m common‐offset procedure was used; for mapping the aquiclude, an R/R (radial‐impact, radial‐geophone—recording predominantly SV), unbalanced‐split‐spread procedure; and for the bedrock channel search, a wide‐angle, T/T (transverse‐impact, transverse‐geophone—recording horizontally polarized shear waves, SH) reflection procedure. The principal result of these investigations is that it is technically feasible through use of shear‐wave methods to obtain reasonable solutions to the first three problems. For the tuff study, wave tests showed phase velocity differences between R/R and T/T recordings indicating shear‐wave splitting, and revealed a fault between blocks of seemingly similar lithology.
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Mayon, Robert Brian, Zoheir Sabeur, Mingyi Tan e Kamal Djidjeli. "ANALYSIS OF FLUID FLOW IMPACT OSCILLATORY PRESSURES WITH AIR ENTRAPMENT AT STRUCTURES". Coastal Engineering Proceedings, n. 35 (23 giugno 2017): 31. http://dx.doi.org/10.9753/icce.v35.structures.31.
Testo completoAbstract (sommario):
Hydrodynamic wave loading at coastal structures is a complex phenomenon to quantify. The chaotic nature of the fluid flow field as waves break against such structures has presented many challenges to Scientists and Engineers for the design of coastal defences. The provision of installations such as breakwaters to resist wave loading and protect coastal areas has evolved predominantly through empirical and experimental observations. This is due to the challenging understanding and quantification of wave impact energy transfer processes with air entrainment at these structures. This paper presents a numerical investigation on wave loading at porous formations including the effects of air entrapment. Porous morphologies generated from cubic packed spheres with varying characteristics representing a breakwater structure are incorporated into the numerical model at the impact interface and the effect on the pressure field is investigated as the wave breaks. We focus on analysing the impulse impact pressure as a surging flow front impacts a porous wall. Thereafter we investigate the multi-modal oscillatory wave impact pressure signals which result from a transient plunging breaker wave impinging upon a modelled porous coastal protective structure. The high frequency oscillatory pressure effects resulting from air entrapment are clearly observed in the simulations. A frequency domain analysis of the impact pressure responses is undertaken. We show that the structural morphology of the porous assembly influences the pressure response signal recorded during the impact event. The findings provide good confidence on the robustness of our numerical model particularly for investigating the air bubbles formation and their mechanics at impact with porous walls.
45
Imai, Yuki, Junichi Ninomiya e Nobuhito Mori. "IMPACT OF RANDOM WAVE SPECTRA ON STOKES DRIFT IN COASTAL CURRENT MODELING". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 1. http://dx.doi.org/10.9753/icce.v36.currents.1.
Testo completoAbstract (sommario):
The wave-induced velocity, known commonly as Stokes drift, plays an important role on upper ocean current system. However, in general, the depth profile tends to be estimated using a regular wave approximation like calculation from significant wave height in order to simplify the modeling. Breivik et al. (2014) proposed an improved Stokes drift profile to considering random waves but discussed limited to deep water. This study proposes a novel treatment of Stokes drift on random waves to consider full directional spectra and the approximated treatment is introduced into coupled ocean-wave model to apply for the depth-limited region. To validate the proposed treatment, Stokes drift velocity derived from the treatment is theoretically and empirically compared with some derived from regular wave approximation. Finally coastal current simulation is performed for Kii channel of Japan focusing on Tanabe bay by the coupled model with two-way-nesting scheme.
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Isaacson, Michael, Norman Allyn e Colleen Ackermann. "Design wave loads for a jetty at Plymouth, Montserrat". Canadian Journal of Civil Engineering 22, n. 6 (1 dicembre 1995): 1084–91. http://dx.doi.org/10.1139/l95-126.
Testo completoAbstract (sommario):
This paper describes the assessment of waves and wave effects with respect to the design of a jetty at Plymouth, Montserrat, in the eastern Caribbean Sea. A previous jetty was destroyed in 1989 by Hurricane Hugo, and a critical part of the new jetty's design relates to the effects of waves. Particular attention is given to the establishment of design wave conditions. This includes both hurricane and non-hurricane conditions and requires a consideration of wave shoaling and refraction, as well as wave breaking in the vicinity of the jetty. The prediction of design wave loads includes the calculation of drag and inertia forces and an assessment of impact loads due to waves on the underside of the jetty and waves breaking onto the deck. Key words: coastal engineering, coastal structures, hydrodynamics, wave forces, wave impact, waves.
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Mitchell, Jamie A., Philip E. Bett, Helen M. Hanlon e Andrew Saulter. "Investigating the impact of climate change on the UK wave power climate". Meteorologische Zeitschrift 26, n. 3 (14 giugno 2017): 291–306. http://dx.doi.org/10.1127/metz/2016/0757.
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Adams-Selin, Rebecca D. "Impact of Convectively Generated Low-Frequency Gravity Waves on Evolution of Mesoscale Convective Systems". Journal of the Atmospheric Sciences 77, n. 10 (1 ottobre 2020): 3441–60. http://dx.doi.org/10.1175/jas-d-19-0250.1.
Testo completoAbstract (sommario):
AbstractIdealized numerical simulations of mesoscale convective systems (MCSs) over a range of instabilities and shears were conducted to examine low-frequency gravity waves generated during initial and mature stages of convection. In all simulations, at initial updraft development a first-order wave was generated by heating extending through the depth of the troposphere. Additional first-order wave modes were generated each time the convective updraft reintensified. Each of these waves stabilized the environment in advance of the system. As precipitation descended below cloud base, and as a stratiform precipitation region developed, second-order wave modes were generated by cooling extending from the midlevels to the surface. These waves destabilized the environment ahead of the system but weakened the 0–5 km shear. Third-order wave modes could be generated by midlevel cooling caused by rear inflow intensification; these wave modes cooled the midlevels destabilizing the environment. The developing stage of each MCS was characterized by a cyclical process: developing updraft, generation of n = 1 wave, increase in precipitation, generation of n = 2 wave, and subsequent environmental destabilization reinvigorating the updraft. After rearward expansion of the stratiform region, the MCSs entered their mature stage and the method of updraft reinvigoration shifted to absorbing discrete convective cells produced in advance of each system. Higher-order wave modes destabilized the environment, making it more favorable to development of these cells and maintenance of the MCS. As initial simulation shear or instability increased, the transition from cyclical wave/updraft development to discrete cell/updraft development occurred more quickly.
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Guirguis, Kristen, Alexander Gershunov, Alexander Tardy e Rupa Basu. "The Impact of Recent Heat Waves on Human Health in California". Journal of Applied Meteorology and Climatology 53, n. 1 (gennaio 2014): 3–19. http://dx.doi.org/10.1175/jamc-d-13-0130.1.
Testo completoAbstract (sommario):
AbstractThis study examines the health impacts of recent heat waves statewide and for six subregions of California: the north and south coasts, the Central Valley, the Mojave Desert, southern deserts, and northern forests. By using canonical correlation analysis applied to daily maximum temperatures and morbidity data in the form of unscheduled hospitalizations from 1999 to 2009, 19 heat waves spanning 3–15 days in duration that had a significant impact on health were identified. On average, hospital admissions were found to increase by 7% on the peak heat-wave day, with a significant impact seen for several disease categories, including cardiovascular disease, respiratory disease, dehydration, acute renal failure, heat illness, and mental health. Statewide, there were 11 000 excess hospitalizations that were due to extreme heat over the period, yet the majority of impactful events were not accompanied by a heat advisory or warning from the National Weather Service. On a regional basis, the strongest health impacts are seen in the Central Valley and the north and south coasts. The north coast contributes disproportionately to the statewide health impact during heat waves, with a 10.5% increase in daily morbidity at heat-wave peak as compared with 8.1% for the Central Valley and 5.6% for the south coast. The temperature threshold at which an impact is seen varies by subregion and timing within the season. These results suggest that heat-warning criteria should consider local percentile thresholds to account for acclimation to local climatological conditions as well as the seasonal timing of a forecast heat wave.
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Kudryavtsev, Vladimir, e Bertrand Chapron. "On Growth Rate of Wind Waves: Impact of Short-Scale Breaking Modulations". Journal of Physical Oceanography 46, n. 1 (gennaio 2016): 349–60. http://dx.doi.org/10.1175/jpo-d-14-0216.1.
Testo completoAbstract (sommario):
AbstractThe wave generation model based on the rapid distortion concept significantly underestimates empirical values of the wave growth rate. As suggested before, inclusion of the aerodynamic roughness modulations effect on the amplitude of the slope-correlated surface pressure could potentially reconcile this model approach with observations. This study explores the role of short-scale breaking modulations to amplify the growth rate of modulating longer waves. As developed, airflow separations from modulated breaking waves result in strong modulations of the turbulent stress in the inner region of the modulating waves. In turn, this leads to amplifying the slope-correlated surface pressure anomalies. As evaluated, such a mechanism can be very efficient for enhancing the wind-wave growth rate by a factor of 2–3.