Capillary-gravity wave resistance in ordinary and magnetic fluids

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 aero 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.