A wave-current model is presented for the simulation of wave characteristics in presence of preexisting current field. A new dispersion relation is derived for the wave-current combined phenomenon and wave-current interactions are simulated by considering Madsen eta/. (1991, 1992) extended Boussinesq equations. The model is applied to a variable water depths for both following and adverse currents, and numerical results are compared with direct experiments and analytical wave-current theory. Concept of equivalent uniform current (Hedges and Lee, 1992) is adopted for the simulation of real current field.
Waves propagation in presence of currents bear considerable importance in coastal or ocean engineering. River discharges, tidal current and near shore current greatly influence wave propagation characteristics in the near shore region. Wave propagation velocity and wave length corresponding to a specific wave frequency will be changed in presence of current field. Amplitude of progressive wave, water particle velocity and acceleration are affected by the presence of currents. Moreover, strong currents change the direction of waves propagation. Recently Sumer and FredsØe (1997) investigated the effect of superimposed currents on scour depth around the head of a vertical-wall breakwater. They found that co-directional currents with regular waves increased scour depth considerably. Longuet-Higgins and Stewart (1961) clarified the mechanism of wave-current interactions by using the concept of radiation stress. They showed that alteration of wave lengths and wave heights relied upon the magnitude of currents in the direction of waves propagation, and energy transfer took place between waves and currents. Later Jonsson et al. (1970) introduced the concept of mean energy level for a wavecurrent field and explained how it affected conservation equations for waves propagation (in presence of currents) over a gently sloping sea bed. Hedges and Lee (1992) presented the concept of equivalent uniform current in wave-cunent computations.
