Large-eddy and large-wave simulation of wave breaking over a constant slope beach using the immersed boundary method

Theofano Koutrouveli, Athanassios Dimas

Monday 29 june 2015

14:20 - 14:35h at Amazon (level 1)

Themes: (T) Water engineering, (ST) River and coastal engineering

Parallel session: 2C. Coastal engineering

Large-eddy and large-wave simulations (LES and LWS) of water wave propagation and breaking over a constant slope beach are presented using the immersed boundary (IB) method. The discretization of the Navier-Stokes equations is done in a Cartesian grid where the bed surface and the free surface are interfaces immersed in the numerical grid. As a result, the implementation of the boundary conditions is achieved through additional terms, which are introduced in the flow equations at the nodes closest to the boundaries (forcing points). Turbulence is modeled by an eddy-viscosity model. The flow is considered to be a two-phase one (water and air) due to the presence of the free surface. The level set method is implemented to treat the free surface evolution. The spatial discretization is based on the use of finite differences on a staggered grid, and a fractional-step method is employed for velocity-pressure coupling. The beach has a constant bed slope of 1/35. The numerical results for the breaking wave height and breaking depth, as well as the free-surface elevation compare well with corresponding experimental data in the literature. In addition, the undertow current is well captured. Vorticity and velocity distributions are presented in the surf zone. Finally, the behavior of the flow in the swash zone is presented.