Christensen et al. (2002)
reviewed the recent advances of numerical modeling and measurement techniques in the surf zone. Three major classes of numerical models in the surf zone were identified, namely, wave-averaged models, phase-resolving Boussinesq-type models, and Navier -Stokes solvers. When the Reynolds Averaged Navier Stokes (RANS) equations are solved, the corresponding computational models are usually referred to as the RANS models. The first RANS model for solving flows in the surf zone was attempted by Lemos (1992). The approach was later refined by Lin and Liu (1998a,b) to simulate both spilling and plunging waves in the surf zone. The computational results were compared to the experimental data by Ting and Kirby (1995, 1996). Since then, a number of studies were made to model waves in the surf zone by using the similar approach but different turbulence closure models (e.g., Bradford, 2000;Mayer and Madsen, 2000). Most of the reported simulations were terminated before waves reach the quasi-steady state to avoid the generation of re-reflected waves from the inflow boundary. This caused the underestimation of undertows (e.g., Lin and Liu, 1998a andBradford, 2000), especially for spilling breakers that need longer time for reaching the quasi-steady state. Based on these observations, Christensen et al. (2002) con