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Tom E Baldock - One of the best experts on this subject based on the ideXlab platform.
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dissipation of incident forced Long Waves in the surf zone implications for the concept of bound wave release at short wave breaking
Coastal Engineering, 2012Co-Authors: Tom E BaldockAbstract:A review of laboratory data sets on surf beat is presented, with a focus on the dissipation of Long wave energy in the surf zone. It is frequently assumed that incident forced Long Waves, or "bound" Long Waves, are released from short wave groups when the short Waves break, subsequently propagating to the shore as a free wave. Free Long Waves may additionally be generated by the moving short wave breakpoint Convincing evidence of the release of forced Long Waves as a result of short wave breaking is lacking, while there appears to be strong evidence to the contrary from a range of recent laboratory experiments. The data from the laboratory experiments are also consistent with field observations of strong nearshore dissipation of Long Waves. These data are also consistent with Longuet-Higgins and Stewart (1962), who suggest that the forced Long wave may reduce in amplitude following short wave breaking, not that it might be released as a free wave. In contrast, forced Long Waves can be progressively "released" from the groups when the short Waves are in shallow water, since these conditions correspond to those where the forced Long wave satisfies the free wave dispersion relationship. This frequently occurs prior to short wave breaking for mild wave conditions, but here it is shown that these conditions are not usually satisfied at the short wave breakpoint for storm conditions. Energy transfers between free and forced Waves are also discussed with regard the data. A surf beat similarity parameter that incorporates both relative beach slope and short wave steepness is suggested, which distinguishes between different Long wave forcing regimes inside the surf zone. (C) 2011 Elsevier B.V. All rights reserved.
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large scale experiments on beach profile evolution and surf and swash zone sediment transport induced by Long Waves wave groups and random Waves
Coastal Engineering, 2011Co-Authors: Tom E Baldock, Ivan Caceres, J A Alsina, Diego Vicinanza, Pasquale Contestabile, Hannah E Power, A SanchezarcillaAbstract:New large-scale laboratory data are presented on the influence of Long Waves, bichromatic wave groups and random Waves on sediment transport in the surf and swash zones. Physical model testing was performed in the large-scale CIEM wave flume at UPC, Barcelona, as part of the SUSCO (swash zone response under grouping storm conditions) experiment in the Hydralab III program (Vicinanza et al., 2010). Fourteen different wave conditions were used, encompassing monochromatic Waves, bichromatic wave groups and random Waves. The experiments were designed specifically to compare variations in beach profile evolution between monochromatic Waves and unsteady Waves with the same mean energy flux. Each test commenced with approximately the same initial profile. The monochromatic conditions were perturbed with free Long Waves, and then subsequently substituted with bichromatic wave groups with different bandwidth and with random Waves with varying groupiness. Beach profile measurements were made at half-hourly and hourly intervals, from which net cross-shore transport rates were calculated for the different wave conditions. Pairs of experiments with slightly different bandwidth or wave grouping show very similar net cross-shore sediment transport patterns, giving high confidence to the data set. Consistent with recent small-scale experiments, the data clearly show that in comparison to monochromatic conditions the bichromatic wave groups reduce onshore transport during accretive conditions and increase offshore transport during erosive conditions. The random Waves have a similar influence to the bichromatic wave groups, promoting offshore transport, in comparison to the monochromatic conditions. The data also indicate that the free Long Waves promote onshore transport, but the conclusions are more tentative as a result of a few errors in the test schedule and modifications to the setup which reduced testing time. The experiments suggest that the inclusion of Long wave and wave group sediment transport is important for improved near-shore morphological modeling of cross-shore beach profile evolution, and they provide a very comprehensive and controlled series of tests for evaluating numerical models. It is suggested that the large change in the beach response between monochromatic conditions and wave group conditions is a result of the increased significant and maximum wave heights in the wave groups, as much as the presence of the forced and free Long Waves induced by the groupiness. The equilibrium state model concept can provide a heuristic explanation of the influence of the wave groups on the bulk beach profile response if their effective relative fall velocity is larger than that of monochromatic Waves with the same incident energy flux.
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sediment transport and beach morphodynamics induced by free Long Waves bound Long Waves and wave groups
Coastal Engineering, 2010Co-Authors: Tom E Baldock, P Manoonvoravong, Kim Son PhamAbstract:New laboratory data are presented on the influence of free Long Waves, bound Long Waves and wave groups on sediment transport in the surf and swash zones. As a result of the very significant difficulties in isolating and identifying the morphodynamic influences of Long Waves and wave groups in field conditions, a laboratory study was designed specifically to enable measurements of sediment transport that resolve these influences. The evolution of model sand beaches, each with the same initial plane slope, was measured for a range of wave conditions, firstly using monochromatic short Waves. Subsequently, the monochromatic conditions were perturbed with free Long Waves and then substituted with bichromatic wave groups with the same mean energy flux. The beach profile changes and net cross-shore transport rates were extracted and compared for the different wave conditions, with and without Long Waves and wave groups. The experiments include a range of wave conditions, e.g. high-energy, moderate-energy, low-energy Waves, which induce both spilling and plunging breakers and different turbulent intensities, and the beaches evolve to form classical accretive, erosive, and intermediate beach states. The data clearly demonstrate that free Long Waves influence surf zone morphodynamics and promote increased onshore sediment transport during accretive conditions and decreased offshore transport under erosive conditions. In contrast, wave groups, which can generate both forced and free Long Waves, generally reduce onshore transport during accretive conditions and increase offshore transport under erosive conditions. The influence of the free Long Waves and wave groups is consistent with the concept of the relative fall velocity, H/wsT, as a dominant parameter controlling net beach erosion or accretion. Free Long Waves tend to reduce H/wsT, promoting accretion, while wave groups tend to increase the effective H/wsT, promoting erosion.
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Long wave generation by the shoaling and breaking of transient wave groups on a beach
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2006Co-Authors: Tom E BaldockAbstract:This paper presents new laboratory data on the generation of Long Waves by the shoaling and breaking of transient-focused short-wave groups. Direct offshore radiation of Long Waves from the breakpoint is shown experimentally for the first time. High spatial resolution enables identification of the relationship between the spatial gradients of the short-wave envelope and the Long-wave surface. This relationship is consistent with radiation stress theory even well inside the surf zone and appears as a result of the strong nonlinear forcing associated with the transient group. In shallow water, the change in depth across the group leads to asymmetry in the forcing which generates significant dynamic setup in front of the group during shoaling. Strong amplification of the incident dynamic setup occurs after short-wave breaking. The data show the radiation of a transient Long wave dominated by a pulse of positive elevation, preceded and followed by weaker trailing Waves with negative elevation. The instantaneous cross-shore structure of the Long wave shows the mechanics of the reflection process and the formation of a transient node in the inner surf zone. The wave run-up and relative amplitude of the radiated and incident Long Waves suggests significant modification of the incident bound wave in the inner surf zone and the dominance of Long Waves generated by the breaking process. It is proposed that these conditions occur when the primary short Waves and bound wave are not shallow water Waves at the breakpoint. A simple criterion is given to determine these conditions, which generally occur for the important case of storm Waves.
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Long wave forcing by the breaking of random gravity Waves on a beach
Proceedings of The Royal Society A: Mathematical Physical and Engineering Sciences, 2002Co-Authors: Tom E Baldock, D A HuntleyAbstract:This paper presents new laboratory data on Long-wave (surf-beat) forcing by the random breaking of shorter gravity water Waves on a plane beach. The data include incident and outgoing wave amplitudes, together with shoreline oscillation amplitudes at Long-wave frequencies, from which the correlation between forced Long Waves and short-wave groups is examined. A detailed analysis of the cross-shore structure of the Long-wave motion is presented, and the observations are critically compared with existing theories for two-dimensional surf-beat generation. The surf beat shows a strong dependency on normalized surf-zone width, consistent with Long-wave forcing by a time-varying breakpoint, with little evidence of the release and reflection of incident bound Long Waves for the random-wave simulations considered. The seaward-propagating Long Waves show a positive correlation with incident short-wave groups and are linearly dependent on short-wave amplitude. The phase relationship between the incident bound Long Waves and radiated free Long Waves is also consistent with breakpoint forcing. In combination with previous work, the present data suggest that the breakpoint variability may be the dominant forcing mechanism during conditions with steep incident short Waves.
L. V. Cherkesov - One of the best experts on this subject based on the ideXlab platform.
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the influence of stratification on the field of wave disturbances generated by a barotropic tide in the vicinity of the mid atlantic ridge
Physical Oceanography, 1997Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:In the framework of the linear theory for the Long Waves occurring in a fluid with a density gradient, the paper concentrates on the field of wave disturbances generated by a barotropic tide in the vicinity of the Mid-Atlantic ridge. Dependences of the wave amplitudes and velocities on the stratification parameters, the angle of onrunning and the period of the barotropic tide have been obtained. A similar study for a model ridge relief of paraboloidal shape has been conducted in ref. 1.
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The effect of currents on the generation of internal Waves by a barotropic tide near an underwater ridge
Physical Oceanography, 1997Co-Authors: E. M. Kolomoitseva, L. V. CherkesovAbstract:In the frame of the linear theory for Long Waves, the paper studies Long Waves generated by a barotropic tide running at an arbitrary angle over a bottom ridge. The ocean is assumed to be two-layered. In the area of a ridge with a rectangular cross section, geostrophic flows are considered, coupled with the inclinations of the free surface and interface. Wave amplitudes are shown to depend on the angle of an onrunning tide and this allows us to reach a conclusion about the influence of a geostrophic current on the generation of internal Waves.
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the impact of stratification on the wave velocity field generated by a barotropic tide impinging upon an oceanic ridge
Physical Oceanography, 1993Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:The horizontal wave velocity field generated by a barotropic tide impinging upon a subwater ridge is considered in the linear theory assumptions for Long Waves. The ocean is assumed to be twolayered, with the tidal wave on-running at an arbitrary angle to the ridge axis. The dependence of the horizontal velocity amplitudes on stratification, the angle of barotropic tide impinging, and the bottom feature geometry is studied.
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the generation of internal Waves by the barotropic tide at an oceanic ridge
Soviet Journal of Physical Oceanography, 1992Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:The generation of internal Waves by the barotropic tide in a two-layer ocean of variable depth is studied within the framework of the linear theory of Long Waves in view of the Coriolis force. The relationships between the internal wave amplitude, the angle of climb of the barotropic tide, and the bottom elevation geometry are studied.
Philip L F Liu - One of the best experts on this subject based on the ideXlab platform.
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Long Waves dissipation and harmonic generation by coastal vegetation
Applied Ocean Research, 2019Co-Authors: Chewei Chang, Philip L F LiuAbstract:Abstract In this paper, we study the harmonic generation and energy dissipation as water Waves propagating through coastal vegetation. Applying the homogenization theory, linear wave models have been developed for a heterogeneous coastal forest in previous works (e.g. [17] , [10] , [11] ). In this study, the weakly nonlinear effects are investigated. The coastal forest is modeled by an array of rigid and vertically surface-piercing cylinders. Assuming monochromatic Waves with weak nonlinearity incident upon the forest, higher harmonic Waves are expected to be generated and radiated into open water. Using the multi-scale perturbation theory, micro-scale flows in the vicinity of cylinders and macro-scale wave dynamics are separated. Expressing the unknown variables (e.g. velocity, free surface elevation) as a superposition of different harmonic components, the governing equations for each mode are derived while different harmonics are interacting with each other because of nonlinearity in the cell problem. Different from the linear models, the leading-order cell problem for micro-scale flow motion, driven by the macro-scale pressure gradient, is now a nonlinear boundary-value-problem, while the wavelength-scale problem for wave dynamics remains linear. A modified pressure correction method is employed to solve the nonlinear cell problem. An iterative scheme is introduced to connect the micro-scale and macro-scale problems. To demonstrate the theoretical results, we consider incident Waves scattered by a homogeneous forest belt in a constant shallow depth. Higher harmonic Waves are generated within the cylinder array and radiated out to the open water region. The comparisons of numerical results obtained by linear and nonlinear models are presented and the behavior of different harmonic components is discussed. The effects of different physical parameters on wave solutions are discussed as well.
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on the runup of Long Waves on a plane beach
Journal of Geophysical Research, 2012Co-Authors: Ichi Chan, Philip L F LiuAbstract:[1] Using the records of free surface fluctuations at several locations during the 2011 Japan Tohoku tsunami, we first show that the leading tsunami Waves in both near-field and far-field regions are small amplitude Long Waves. These leading Waves are very different from solitary Waves. We then focus on investigating the evolution and runup of non-breaking Long Waves on a plane beach, which is connected to a constant depth region. For this purpose, we develop a Lagrangian numerical model to solve the nonlinear shallow water equations. The Lagrangian approach tracks the moving shoreline directly without invoking any additional approximation. We also adopt and extend the analytical solutions by Synolakis (1987) and Madsen and Schaffer (2010) for runup and rundown of cnoidal Waves and a train of multiple solitary Waves. The analytical solutions for cnoidal Waves compare well with the existing experimental data and the direct numerical results when wave amplitudes are small. However, large discrepancies appear when the incident amplitudes are finite. We also examine the relationship between the maximum runup height and the leading wave form. It is concluded that for a single wave the accelerating phase of the incident wave controls the maximum runup height. Finally, using the analytical solutions for the approximated wave forms of the leading tsunamis recorded at Iwate South station from the 2011 Tohoku Japan tsunami, we estimate the runup height.
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Long Waves through emergent coastal vegetation
Journal of Fluid Mechanics, 2011Co-Authors: Chiang C Mei, Philip L F Liu, Ichi Chan, Zhenhua Huang, Wenbin ZhangAbstract:We study the effects of emergent coastal forests on the propagation of Long surface Waves of small amplitude. The forest is idealized by an array of vertical cylinders. Simple models are employed to represent bed friction and to simulate turbulence generated by flow through the tree trunks. A multi-scale (homogenization) analysis similar to that for seepage flows is carried out to deduce the effective equations on the macro-scale. The effective coefficients are calculated by numerically solving the micro-scale problem in a unit cell surrounding one or several cylinders. Analytical and numerical solutions for wave attenuation on the macro-scale for different bathymetries and coastal forest configurations are presented. For a transient incident wave, analytical results are discussed for the damping of a leading tsunami. For comparison series of laboratory data for periodic and transient incident Waves are also presented. Good agreement is found even though some of the measured Waves are short or nonlinear.
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advanced numerical models for simulating tsunami Waves and runup
Advances in Coastal and Ocean Engineering, 2008Co-Authors: Philip L F Liu, Harry Yeh, Cosras SynolakisAbstract:Modeling Runup with Depth-Integrated Equation Models (G Pedersen) High-Resolution Finite Volume Methods for the Shallow Water Equations with Bathymetry and Dry States (R J LeVeque & D L George) SPH Modeling of Tsunami Waves (B D Rogers & R A Dalrymple) A Large Eddy Simulation Model for Tsunami and Runup Generated by Landslides (T-R Wu & P L-F Liu) Free-Surface Lattice Boltzmann Modeling (J B Frandsen) Description of Benchmark Problems (P L-F Liu et al.) Tsunami Runup onto a Plane Beach (Z Kowalik et al.) Nonlinear Evolution of Long Waves over a Sloping Beach (U Kanoglu) Amplitude Evolution and Runup of Long Waves, Comparison of Experimental and Numerical Data on a 3D Complex Topography (A C Yalciner et al.) Numerical Simulations of Tsunami Runup onto a Three-Dimensional Beach with Shallow Water Equations (X Wang et al.) 3D Numerical Simulation of Tsunami Runup onto a Complex Beach (T Kakinuma) Evaluating Wave Propagation and Inundation Characteristics of the Most Tsunami Model over a Complex 3D Beach (A Chawla et al.) Tsunami Propagation and Runup due to a 2D Landslide (Z Kowalik et al.) Boussinesq Modeling of Landslide-Generated Waves and Tsunami Runup (O Nwogu) Numerical Simulation of Tsunami Runup onto a Complex Beach with a Boundary-Fitting Cell System (H Yasuda) A 1D Lattice Boltzmann Model Applied to Tsunami Runup onto a Plane Beach (J B Frandsen).
S. V. Dovgaya - One of the best experts on this subject based on the ideXlab platform.
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the influence of stratification on the field of wave disturbances generated by a barotropic tide in the vicinity of the mid atlantic ridge
Physical Oceanography, 1997Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:In the framework of the linear theory for the Long Waves occurring in a fluid with a density gradient, the paper concentrates on the field of wave disturbances generated by a barotropic tide in the vicinity of the Mid-Atlantic ridge. Dependences of the wave amplitudes and velocities on the stratification parameters, the angle of onrunning and the period of the barotropic tide have been obtained. A similar study for a model ridge relief of paraboloidal shape has been conducted in ref. 1.
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the impact of stratification on the wave velocity field generated by a barotropic tide impinging upon an oceanic ridge
Physical Oceanography, 1993Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:The horizontal wave velocity field generated by a barotropic tide impinging upon a subwater ridge is considered in the linear theory assumptions for Long Waves. The ocean is assumed to be twolayered, with the tidal wave on-running at an arbitrary angle to the ridge axis. The dependence of the horizontal velocity amplitudes on stratification, the angle of barotropic tide impinging, and the bottom feature geometry is studied.
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the generation of internal Waves by the barotropic tide at an oceanic ridge
Soviet Journal of Physical Oceanography, 1992Co-Authors: S. V. Dovgaya, L. V. CherkesovAbstract:The generation of internal Waves by the barotropic tide in a two-layer ocean of variable depth is studied within the framework of the linear theory of Long Waves in view of the Coriolis force. The relationships between the internal wave amplitude, the angle of climb of the barotropic tide, and the bottom elevation geometry are studied.
S Contardo - One of the best experts on this subject based on the ideXlab platform.
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free and forced components of shoaling Long Waves in the absence of short wave breaking
Journal of Physical Oceanography, 2021Co-Authors: S Contardo, Ryan J Lowe, Jeff E Hansen, Dirk P Rijnsdorp, Francois Dufois, Graham SymondsAbstract:Long Waves are generated and transform when short-wave groups propagate into shallow water, but the generation and transformation processes are not fully understood. In this study we develop an analytical solution to the linearized shallow-water equations at the wave-group scale, which decomposes the Long Waves into a forced solution (a bound Long wave) and free solutions (free Long Waves). The solution relies on the hypothesis that free Long Waves are continuously generated as short-wave groups propagate over a varying depth. We show that the superposition of free Long Waves and a bound Long wave results in a shift of the phase between the short-wave group and the total Long wave, as the depth decreases prior to short-wave breaking. While it is known that short-wave breaking leads to free-Long-wave generation, through breakpoint forcing and bound-wave release mechanisms, we highlight the importance of an additional free-Long-wave generation mechanism due to depth variations, in the absence of breaking. This mechanism is important because as free Long Waves of different origins combine, the total free-Long-wave amplitude is dependent on their phase relationship. Our free and forced solutions are verified against a linear numerical model, and we show how our solution is consistent with prior theory that does not explicitly decouple free and forced motions. We also validate the results with data from a nonlinear phase-resolving numerical wave model and experimental measurements, demonstrating that our analytical model can explain trends observed in more complete representations of the hydrodynamics.
