Reverse Steady Streaming Induced by a Freely Moving Wavy Wall

Recently, Figueroa et al. demonstrated that steady streaming can be generated by the oscillatory motion of a floating magnet driven by electromagnetic forcing in a shallow electrolytic layer. They also found that the rotation direction of the resulting steady vortices is opposite to that of classical streaming flows. In this work, we present a theoretical and experimental investigation of the fluid–structure interaction between a freely moving wall and an oscillatory flow. Our objective is to elucidate the coupling mechanism between the fluid and the oscillating body that gives rise to reverse streaming and to apply this analysis to the case of a freely moving wavy wall. The flow is analyzed theoretically and an analytical solution is obtained using a perturbation method. Experimental results based on Particle Image Velocimetry are also presented, where an oscillatory flow generated by an electromagnetic force in an electrolyte layer drives a wavy wall floating on the surface. The results confirm the occurrence of reverse streaming and demonstrate that the flow dynamics depend on the density ratio between the freely moving solid and the fluid. The analytical solution qualitatively captures the behavior observed in the experiments.