Experimental study on the evolution of traveling waves over an undulated incline

Abstract

We present experimental results on the evolution of traveling waves over a strongly undulated incline. In order to investigate the difference between waves in the linearly stable and unstable region, we set the Reynolds number near the neutral curve. That way, we were able to cross the neutral curve by increasing the frequency of excitation, without changing the velocity field of the basic flow. The amplitude of excitation was also varied, to analyze the evolution of both linear and nonlinear waves. We report on a rich variety of phenomena, including: (a) energy transfer from the excitation frequency to its higher harmonics, (b) the growth rate of the traveling waves, (c) the stability of traveling waves depending on its amplitude, and (d) the amplitude of saturation depending on the excitation frequency. We compare our results to those so far available in the literature. To our knowledge, this is the first experimental work on the development of traveling waves over strongly undulated substrate geometries.