Flexible Boundary Conditions for a Boussinesq-Type Wave Model

A procedure is presented for the dynamic handling of the boundaries of Boussinesq-type wave models that enables to control the reflection properties. The main purpose of the procedure is the reduction of spurious reflections at open boundaries. The procedure also allows, however, the modeling of partial reflection at closed boundaries. The approach chosen takes into account the effect of wave direction, wave period, and wave height, in order that irregular waves, waves at arbitrary angles, and steep waves can all be handled properly. An innovative aspect of the developed method is that it can equally well be used for strongly dispersive waves, since besides the angle of outgoing waves also the celerity is determined dynamically. The results presented demonstrate the feasibility of the approach; reflection coefficients of only about 1% are obtained for regular waves, varying angle, period, as well as steepness.