NUMERICAL MODELLING OF KINEMATICS AND DYNAMICS OF SPILLING AND PLUNGING BREAKERS IN SHALLOW WATERS
AbstractWave breaking is a complex two-phase flow process that strongly influences the air-water interaction. A number of physical processes are involved in the exchange of mass, momentum and energy between air and water interaction during the wave breaking process. In shallow waters, waves undergo different transformation processes such as shoaling, refraction, diffraction and breaking due to their non-linear interaction with the seabed. Thus, the associated hydrodynamics are rather complicated to understand when compared to wave breaking in deep water (Lin, 2008). In the present numerical study, a two phase flow CFD model REEF3D (Bihs et al. 2016) is used to model and investigate the hydrodynamics of spilling and plunging breakers over a slope. An accurate modeling of the wave breaking process is still highly demanding due to the strong non-linear air-water interaction and turbulent production at the free surface. The numerical wave tank is based on the incompressible Reynolds Averaged Navier-Stokes (RANS) equations together with the level set method for free surface and the k-Ï‰ model for turbulence (Alagan Chella et al. 2015). The model uses the 5th-order Weighted Essentially Non- Oscillatory (WENO) scheme for the convective discretization and the 3rd-order TVD Runge Kutta Scheme for the time discretization. A staggered grid method is employed in the model in order to achieve a stronger coupling between the pressure and velocity. The model is fully parallelized with the domain decomposition method and MPI (Message passing interface).
Bihs, H., Kamath, A., Alagan Chella, M., Aggarwal, A., Arntsen, Ã˜.A., 2016. A new level set numerical wave tank with improved density interpolation for complex wave hydrodynamics. Computers and Fluids 140, 191-208.
Alagan Chella, M., Bihs, H., Myrhaug, D. and Muskulus, M. (2016), Hydrodynamic characteristics and geometric properties of plunging and spilling breakers over impermeable slopes, Ocean Modelling, 103, 53-72.
Lin, P. (2008), Numerical modeling of water waves, CRC Press.
Ting, F.C., Kirby, J.T., 1994. Observation of undertow and turbulence in a laboratory surf zone. Coastal Engineering, 24, 51-80
Kjeldsen, S.P., Myrhaug, D., 1978. Kinematics and Dynamics of Breaking Waves. Technical Report. River and Harbour Laboratory (NHL), The Norwegian Institute of Technology.