The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
David Apsley - One of the best experts on this subject based on the ideXlab platform.
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Random Wave runup and overtopping a steep sea wall shallow water and boussinesq modelling with generalised breaking and wall impact algorithms validated against laboratory and field measurements
Coastal Engineering, 2013Co-Authors: Maurice Mccabe, Peter Stansby, David ApsleyAbstract:Abstract A semi-implicit shallow-water and Boussinesq model has been developed to account for Random Wave breaking, impact and overtopping of steep sea walls including recurves. At a given time breaking is said to occur if the Wave height to water depth ratio for each individual Wave exceeds a critical value of 0.6 and the Boussinesq terms are simply switched off. The example is presented of Waves breaking over an offshore reef and then ceasing to break as they propagate inshore into deeper water and finally break as they run up a slope. This is not possible with the conventional criterion of a single onset of breaking based on rate of change of surface elevation which was also found to be less effective generally. The runup distribution on the slope inshore of the reef was well predicted. The model is tested against field data for overtopping available for Anchorsholme, Blackpool and corresponding 1:15 scale Wave flume tests. Reflection of breaking Waves impacting a steep sea wall is represented as a partial reversal of momentum flux with an empirically defined coefficient. Offshore to nearshore significant Wave height variation was reasonably predicted although nearshore model spectra showed distinct differences from the experiments. The breaking Wave shape described by a shape parameter was also not well represented as might be expected for such a simple model. Overtopping agreement between model, field and flume was generally good although repeatability of two nominally identical flume experiments was only within 25%. Different distributions of Random phase between spectral components can cause overall overtopping rates to differ by up to a factor of two. Predictions of mean discharge by EurOtop methods were within a factor of two of experimental measurements.
Maurice Mccabe - One of the best experts on this subject based on the ideXlab platform.
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Random Wave runup and overtopping a steep sea wall shallow water and boussinesq modelling with generalised breaking and wall impact algorithms validated against laboratory and field measurements
Coastal Engineering, 2013Co-Authors: Maurice Mccabe, Peter Stansby, David ApsleyAbstract:Abstract A semi-implicit shallow-water and Boussinesq model has been developed to account for Random Wave breaking, impact and overtopping of steep sea walls including recurves. At a given time breaking is said to occur if the Wave height to water depth ratio for each individual Wave exceeds a critical value of 0.6 and the Boussinesq terms are simply switched off. The example is presented of Waves breaking over an offshore reef and then ceasing to break as they propagate inshore into deeper water and finally break as they run up a slope. This is not possible with the conventional criterion of a single onset of breaking based on rate of change of surface elevation which was also found to be less effective generally. The runup distribution on the slope inshore of the reef was well predicted. The model is tested against field data for overtopping available for Anchorsholme, Blackpool and corresponding 1:15 scale Wave flume tests. Reflection of breaking Waves impacting a steep sea wall is represented as a partial reversal of momentum flux with an empirically defined coefficient. Offshore to nearshore significant Wave height variation was reasonably predicted although nearshore model spectra showed distinct differences from the experiments. The breaking Wave shape described by a shape parameter was also not well represented as might be expected for such a simple model. Overtopping agreement between model, field and flume was generally good although repeatability of two nominally identical flume experiments was only within 25%. Different distributions of Random phase between spectral components can cause overall overtopping rates to differ by up to a factor of two. Predictions of mean discharge by EurOtop methods were within a factor of two of experimental measurements.
Dag Myrhaug - One of the best experts on this subject based on the ideXlab platform.
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Aspects of Random Wave Scour Around Structures
2020Co-Authors: Dag Myrhaug, Alf TørumAbstract:The stochastic properties of the scour characteristics below a fixed pipeline, around a single slender vertical pile with circular cross section as well as at the round head of rubble-mound breakwater in Random Waves are investigated. It is demonstrated how formulas valid for regular Waves can be used to find the cumulative distribution functions for the scour characteristics by assuming the free surface elevation to be a stationary Gaussian narrow-band Random process. The results are compared with data for Random Wave scour.
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Random Wave-induced current on mild slopes
Ocean Modelling, 2015Co-Authors: Dag MyrhaugAbstract:Abstract This paper provides a simple analytical method for calculating the Wave-induced current due to long-crested Random Waves on mild slopes. The approach is based on assuming the Waves to be a stationary Random process, adopting the Battjes and Groenendijk (2000) Wave height distribution for mild slopes. An example is included to demonstrate the application of the analytical method for practical purposes using data typical for field conditions; the significant values of the surface Stokes drift and the volume Stokes transport are calculated. The present results can be used to make assessment of the Random Wave-induced current based on available Wave statistics.
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Long- and short-crested Random Wave-induced scour below pipelines
Proceedings of the Institution of Civil Engineers - Maritime Engineering, 2011Co-Authors: Dag Myrhaug, Ong Muk ChenAbstract:This paper provides a stochastic method by which the maximum scour depth and the maximum scour width below pipelines exposed to long-crested (2-D) and short-crested (3-D) non-linear Random Waves can be derived. The approach is based on assuming the Waves to be a stationary narrow-band Random process and adopting the Forristall Wave crest height distribution representing both 2-D and 3-D non-linear Random Waves, and by using the regular Wave formulae for scour depth and scour width derived in earlier research studies. An example calculation is provided. Tentative approaches to related Random Wave-induced scour cases are also suggested.
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Random Wave-induced scour at the trunk section of a breakwater
Coastal Engineering, 2009Co-Authors: Dag MyrhaugAbstract:Abstract This paper provides a stochastic method by which the Random Wave-induced scour depth at the trunk section of vertical-wall and rubble-mound breakwaters can be derived. Here the formulas for regular Wave-induced scour depth provided by Xie [Xie, S.L., 1981. Scouring patterns in front of vertical breakwaters and their influence on the stability of the foundations of the breakwaters. Report. Department of Civil Engineering, Delft University of Technology, Delft, The Netherlands, September, 61 pp.] for vertical-wall breakwater and Sumer and Fredsoe [Sumer, B.M., Fredsoe, J., 2000. Experimental study of 2D scour and its protection at a rubble-mound breakwater. Coast. Eng. 40, 59–87] for rubble-mound breakwater are used. These formulas are combined with describing the Waves as a stationary Gaussian narrow-band Random process to derive the Random Wave-induced scour depth. Comparisons are made between the present method and the Sumer and Fredsoe [Sumer, B.M., Fredsoe, J., 2000. Experimental study of 2D scour and its protection at a rubble-mound breakwater. Coast. Eng. 40, 59–87.] Random Wave scour data for rubble-mound breakwater, as well as the Hughes and Fowler [Hughes, S.A., Fowler, J.A., 1991. Wave-induced scour predictions at vertical walls. ASCE Proc. Conf. Coastal Sediments vol. 91, 1886–1899] Random Wave scour data and formula for vertical-wall breakwater. A tentative approach to Random Wave-induced scour at a vertical impermeable submerged breakwater is also suggested.
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Scour below pipelines and around vertical piles in Random Waves
Coastal Engineering, 2003Co-Authors: Dag MyrhaugAbstract:An approach by which the scour depth and scour width below a fixed pipeline and scour depth around a circular vertical pile in Random Waves can be derived is presented. Here, the scour depth formulas by Sumer and Fredsoe [ASCE J. Waterw., Port, Coastal Ocean Eng. 116 (1990) 307] for pipelines and Sumer et al. [ASCE J. Waterw., Port, Coastal Ocean Eng. 114 (1992) 599] for vertical piles as well as the scour width formula by Sumer and Fredsoe [The Mechanics of Scour in the Marine Environment, World Scientific, Singapore, 2002] for pipelines combined with describing the Waves as a stationary Gaussian narrow-band Random process are used to derive the cumulative distribution functions of the scour depths and width. Comparisons are made between the present approach and Random Wave scour data. Tentative approaches to related Random Wave scour cases are also suggested.
Felice Arena - One of the best experts on this subject based on the ideXlab platform.
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field experiment on Random Wave forces acting on vertical cylinders
Probabilistic Engineering Mechanics, 2012Co-Authors: Paolo Boccotti, Felice Arena, Vincenzo Fiamma, Giuseppe BarbaroAbstract:Abstract The accuracy of the Morison equation for Wave forces acting on cylinders was tested by conducting a field experiment at the Natural Ocean Engineering Laboratory (NOEL) using a database of about 69,000 individual wind Waves. The test was conducted by comparing two stationary Random forces as a function of time: F a ( t ) , the measured Wave force, and F c ( t ) , the Wave force calculated using the Morison equation. The particle velocity and acceleration components of the Morison equation were obtained using the linear theory of wind-generated Waves from the directional Wave spectrum obtained by measuring the Wave elevation. The inertia coefficient C i n and drag coefficient C d g are given as a function of the Keulegan–Carpenter number K E and Reynolds number R E for K E in (0, 20) and R E in ( 2 ⋅ 10 4 , 2 ⋅ 10 5 ) . The trend of our data was compatible with the asymptotic values of C i n and C d g suggested by Sarpkaya for large values of R E .
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mechanics of nonlinear Random Wave groups interacting with a vertical wall
Physics of Fluids, 2008Co-Authors: Alessandra Romolo, Felice ArenaAbstract:Nonlinear Random Wave groups interacting with a vertical wall are investigated. The analytical solution for the second-order free surface displacement and velocity potential when a high crest occurs at some fixed point on, or close to, the vertical wall is obtained. The solution is exact for any water depth, and it is given as a function of the frequency spectrum of the incident Waves. It is obtained that the effects of nonlinearity strongly modify the linear structure of Wave groups both in the space and the time domain. The maximum effect of nonlinearity occurs when the high Wave hits the wall. Furthermore, it is shown that in finite water depth, the nonlinearity increases as the bottom depth decreases. Finally, a validation by means of Monte Carlo simulations of nonlinear Random Waves in reflection is given.
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Non-Linear Random Wave Groups With a Superimposed Current
Volume 3: Safety and Reliability; Materials Technology; Douglas Faulkner Symposium on Reliability and Ultimate Strength of Marine Structures, 2006Co-Authors: Vincenzo Nava, Felice Arena, Alessandra RomoloAbstract:In this paper a new solution for non-linear Random Wave groups in the presence of a uniform current is obtained, by extending to the second-order the Boccotti’s ‘Quasi-Determinism’ (QD) theory. The second formulation of the QD theory gives the mechanics of linear Random Wave groups when a large crest-to-trough Wave height occurs. Here the linear QD theory is firstly applied to the Wave-current interaction. Therefore the nonlinear expressions both of free surface displacement and velocity potential are obtained, to the second-order in a Stokes’ expansion. Finally some numerical applications are presented in order to analyze both the Wave profile and the Wave kinematics.Copyright © 2006 by ASME
Peter Stansby - One of the best experts on this subject based on the ideXlab platform.
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Random Wave runup and overtopping a steep sea wall shallow water and boussinesq modelling with generalised breaking and wall impact algorithms validated against laboratory and field measurements
Coastal Engineering, 2013Co-Authors: Maurice Mccabe, Peter Stansby, David ApsleyAbstract:Abstract A semi-implicit shallow-water and Boussinesq model has been developed to account for Random Wave breaking, impact and overtopping of steep sea walls including recurves. At a given time breaking is said to occur if the Wave height to water depth ratio for each individual Wave exceeds a critical value of 0.6 and the Boussinesq terms are simply switched off. The example is presented of Waves breaking over an offshore reef and then ceasing to break as they propagate inshore into deeper water and finally break as they run up a slope. This is not possible with the conventional criterion of a single onset of breaking based on rate of change of surface elevation which was also found to be less effective generally. The runup distribution on the slope inshore of the reef was well predicted. The model is tested against field data for overtopping available for Anchorsholme, Blackpool and corresponding 1:15 scale Wave flume tests. Reflection of breaking Waves impacting a steep sea wall is represented as a partial reversal of momentum flux with an empirically defined coefficient. Offshore to nearshore significant Wave height variation was reasonably predicted although nearshore model spectra showed distinct differences from the experiments. The breaking Wave shape described by a shape parameter was also not well represented as might be expected for such a simple model. Overtopping agreement between model, field and flume was generally good although repeatability of two nominally identical flume experiments was only within 25%. Different distributions of Random phase between spectral components can cause overall overtopping rates to differ by up to a factor of two. Predictions of mean discharge by EurOtop methods were within a factor of two of experimental measurements.
