Capillary-gravity wave resistance in ordinary and magnetic fluids

¹ Groupe Ferrofluide associé à l'Université Denis Diderot, Laboratoire des Milieux Désordonnés et Hétérogènes, UMR CNRS 7603 Université Pierre et Marie Curie case 86, 4 place Jussieu, 75231 Paris Cedex 05, France
² Department of Mechanical Engineering, Ben-Gurion University of the Negev P.O.B. 653, Beer-Sheva 84105, Israel

Corresponding author: browaeys@ccr.jussieu.fr

Received: 8 March 2000
Accepted: 8 November 2000

Abstract

Wave resistance is the drag force associated to the emission of waves by a moving disturbance at a free fluid surface. In the case of capillary-gravity waves it undergoes a transition from zero to a finite value as the speed of the disturbance reaches a certain critical value. For the first time an experiment is designed in order to obtain the capillary-gravity wave resistance as a function of speed. The effect of viscosity is explored, and a magnetic fluid is used to extend the available range of critical speeds. The threshold values are in good agreement with the proposed theory. Contrary to the theoretical model, however, the measured wave resistance reveals a non-monotonic speed dependence after the threshold.