PARAMETRIC-INSTABILITY OF A LIQUID-VAPOR INTERFACE CLOSE TO THE CRITICAL-POINT

An experimental study of the parametric instability of a liquid-vapor interface close to the critical point is presented. A cell containing carbon dioxide at the critical density is vertically vibrated sinusoidally; the acceleration amplitude a0 and the instability wavelength lambda-0 at the instability onset are measured with respect to the excitation frequency and the critical temperature difference T(c)-T. These measurements provide a simple way to determine the surface tension and the density difference between the two phases. When T(c)-T diminishes lambda-0 decreases and reaches a finite value whereas a0 diverges. The shape of the wave pattern appears to depend on T(c)-T.