scholarly journals MODELING SHEET FLOW UNDER BREAKING WAVES ON A SURF ZONE SANDBAR

2018 ◽  
pp. 58
Author(s):  
Yeulwoo Kim ◽  
Ryan C. Mieras ◽  
Zhen Cheng ◽  
Tian-Jian Hsu ◽  
Jack A. Puleo
Keyword(s):  
Boundary Layer ◽  
Free Surface ◽  
Sediment Transport ◽  
Numerical Model ◽  
Wave Breaking ◽  
Surf Zone ◽  
Free Stream ◽  
Breaking Waves ◽  
Bottom Boundary Layer ◽  
Horizontal Pressure

Wave-driven sediment transport is one of the main drivers of beach morphodynamics. However, the creation of a comprehensive numerical model remains to be a challenging task due to complex mechanisms associated with unsteadiness and free-surface effects. Particularly for highly non-linear and skewed-asymmetric breaking waves, the boundary layer approximation (i.e., assuming horizontal pressure gradient is equal to local free-stream acceleration) is questionable. Moreover, wave-breaking-induced turbulence may approach the bed and further enhance sediment transport. Thus, a numerical model that can resolve the entire water column from the bottom boundary layer to the free-surface can be a powerful tool to understand wave-driven sediment transport.

scholarly journals Explosive ripple instability due to incipient wave breaking

2019 ◽  
Vol 863 ◽  
pp. 876-892
Author(s):  
Alexei A. Mailybaev ◽  
André Nachbin
Keyword(s):  
Free Surface ◽  
Wave Breaking ◽  
Surf Zone ◽  
Asymptotic Expression ◽  
Nonlinear Effects ◽  
Finite Depth ◽  
Breaking Waves ◽  
Theory Model ◽  
Intrinsic Frequency ◽  
Strong Compression

Considering two-dimensional potential ideal flow with a free surface and finite depth, we study the dynamics of small-amplitude and short-wavelength wavetrains propagating in the background of a steepening nonlinear wave. This can be seen as a model for small ripples developing on the slopes of breaking waves in the surf zone. Using the concept of wave action as an adiabatic invariant, we derive an explicit asymptotic expression for the change of ripple steepness. Through this expression, nonlinear effects are described using the intrinsic frequency and intrinsic gravity along Lagrangian (material) trajectories on a free surface. We show that strong compression near the tip on the wave leads to an explosive ripple instability. This instability may play an important role in the understanding of fragmentation and whitecapping at the surface of breaking waves. Analytical results are confirmed by numerical simulations using a potential theory model.

A numerical study of breaking waves in the surf zone

1998 ◽  
Vol 359 ◽  
pp. 239-264 ◽  
Author(s):  
PENGZHI LIN ◽  
PHILIP L.-F. LIU
Keyword(s):  
Experimental Data ◽  
Free Surface ◽  
Numerical Model ◽  
Kinetic Energy ◽  
Turbulent Kinetic Energy ◽  
Surf Zone ◽  
Breaking Waves ◽  
Numerical Results ◽  
Long Distance ◽  
The Mean

This paper describes the development of a numerical model for studying the evolution of a wave train, shoaling and breaking in the surf zone. The model solves the Reynolds equations for the mean (ensemble average) flow field and the k–ε equations for the turbulent kinetic energy, k, and the turbulence dissipation rate, ε. A nonlinear Reynolds stress model (Shih, Zhu & Lumley 1996) is employed to relate the Reynolds stresses and the strain rates of the mean flow. To track free-surface movements, the volume of fluid (VOF) method is employed. To ensure the accuracy of each component of the numerical model, several steps have been taken to verify numerical solutions with either analytical solutions or experimental data. For non-breaking waves, very accurate results are obtained for a solitary wave propagating over a long distance in a constant depth. Good agreement between numerical results and experimental data has also been observed for shoaling and breaking cnoidal waves on a sloping beach in terms of free-surface profiles, mean velocities, and turbulent kinetic energy. Based on the numerical results, turbulence transport mechanisms under breaking waves are discussed.

scholarly journals LABORATORY EXPERIMENTS ON THE INFLUENCE OF WIND ON NEARSHORE WAVE BREAKING

1988 ◽  
Vol 1 (21) ◽  
pp. 46
Author(s):  
Scott L. Douglass ◽  
J. Richard Weggel
Keyword(s):  
Wind Direction ◽  
Wave Breaking ◽  
Laboratory Experiments ◽  
Surf Zone ◽  
Breaking Waves ◽  
Wave Tank ◽  
Zone Width

The influence of wind on nearshore breaking waves was investigated in a laboratory wave tank. Breaker location, geometry, and type depended upon the wind acting on the wave as it broke. Onshore winds tended to cause waves to break earlier, in deeper water, and to spill: offshore winds tended to cause waves to break later, in shallower water, and to plunge. A change in wind direction from offshore to onshore increased the surf zone width by up to 100%. Wind's effect was greatest for waves which were near the transition between breaker types in the absence of wind. For onshore winds, it was observed that microscale breaking can initiate spilling breaking by providing a perturbation on the crest of the underlying wave as it shoals.

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