AN EXPERIMENTAL-STUDY OF THE ONSET OF PARAMETRICALLY PUMPED SURFACE-WAVES IN VISCOUS FLUIDS

We measure the threshold accelerations necessary to excite surface wav es in a vertically vibrated fluid container (the Faraday instability). Under the proper conditions, the thresholds and onset wavelengths agr ee with recent theoretical predictions for a laterally infinite, finit e-depth container filled with a viscous fluid. Experimentally, we show that by using a viscous, non-polar fluid, the finite-size effects of sidewalls and the effects of surface contamination can be made negligi ble. We also show that finite-size corrections are of order h/L, where h is the fluid depth and L the container size. Based on these measure ments, one can more easily interpret certain unexpected observations f rom previous experimental studies of the Faraday instability.