Nonlinear Effects in Resonantly Driven Surface Waves on Fluids
The results presented in this paper show that fluid surface waves, resonantly driven by spatially nonuniform, time periodic electric fields, exhibit nonlinear effects when the wave amplitude ξ exceeds a significant fraction of the distance D between the driver electrode and the fluid surface. The phase difference between the surface wave and the driving force, as well as the dependence of wave amplitude on the electric stress are computed and compared with experimental results. For ξ/D exceeding ~0.7 (dependent on electrode geometry) the surface waves excited are unstable (also confirmed experimentally). The experiments are performed on surface waves on mercury contained in a cylindrical microwave resonator. Shifts in the microwave resonant frequency (caused by the surface waves) monitor the displacement of the fluid surface.