Finite Element Modeling of Nearshore Currents

A finite element model is developed to compute the nearshore currents induced by breaking waves in the surf zone. The normal incident wave system is employed so as to study the effects of beach topography on the current circulation patterns. The beach topography considered here is of linear plane beach shape with minor undulations in the longshore direction. Ignoring the lateral turbulent diffusion, the finite element representation of the governing equations of mean currents is obtained by the method of weighted residuals. It is shown that, due to the flexible grid discretization, this model can be used to study problems containing more complex beach topography within a large area of interest. Two types of alongshore beach undulations are investigated: rhythmic topography and localized irregular topography. The locations of rip currents depend on the surf zone width and the on-offshore variation of beach profile.