Transient and steady drift currents in waves damped by surfactants

In this paper we study the Lagrangian mean drift induced by spatially damped capillary-gravity waves on a surface covered by an elastic film. The analysis is developed with regard to a typical laboratory setup, and explicit solutions for both transient and steady horizontal drift velocities are a given. We consider a situation where the film covers the entire surface and is prevented from drifting away, e.g., by a film barrier. The drift below an inextensible film resembles the drift under an ice cover, with a jetlike current in the wave propagation direction just below the surface. If the film is elastic the solution changes drastically. For certain values of the film elasticity parameter the mean flow is in the direction opposite to that of wave propagation in the upper part of the water column. (C) 2005 American Institute of Physics.