Surface wave propagation over slowly varying media of topography and non-uniform three-dimensional currents

摘要

The influence of ambient current fields on the mild-slope approximation is reassessed using the Hamiltonian variational principle. Considering the slowly modulated non-uniform currents which may possess both verti- Cal and horizontal variations, the extended mild-slope equation for surface waves propagating over slowly varying topogra- phy is derived. It is found that for large current velocities comparable to the wave celerity and the group velocity, the ex- Tended mild-slope equation is valid. For the validity of the geometric optics-approximation, additional conditions con- Cerning current fields should be satisfied.