Capillary-gravity waves on depth-dependent currents: Consequences for the wave resistance

We study theoretically the capillary-gravity waves created at the water-air interface by a small two-dimensional perturbation in the frequently encountered case where a depth-dependent current is present in the fluid. Assuming linear wave theory, we derive a general expression of the wave resistance experienced by the perturbation as a function of the current profile in the case of an inviscid fluid. We then illustrate the use of this expression in the case of constant vorticity