The conformal-mapping method for surface gravity waves in the presence of variable bathymetry and mean current

The conformal mapping formulation for the free-surface Euler equations in the presence of non homogeneous, yet stationary bathymetry is here derived and numerically implemented. The differences arising with respect to the more familiar flat-bottom and deep-water versions of the method are examined in detail. It is also shown how the loss of translational invariance due to the variable bottom profile naturally leads to consider a further extension of the method, which accounts for the superposition-otherwise immaterial-of an irrotational mean stream. As it is illustrated by numerical examples, the formulation presented is suitable for the study of fully nonlinear wave-topography and wave-current interactions realized by combining mean current and variable bathymetry.