Frozen wave induced by high frequency horizontal vibrations on aCO2liquid-gas interface near the critical point

We used the liquid-vapor equilibrium of CO2 near its critical point (T(C)-T=1 to 150 mK) in order to study the stability of an interface between a gas and a liquid having close densities rho(L) approximately rho(V) when submitted to high frequency f (3-57.5 Hz) horizontal vibrations (of amplitude a from 0.1 to 2.5 mm). Above a given velocity threshold (2piaf )(0) we observed a "frozen wave," corresponding to an interface profile of sinelike shape which is stationary in the reference frame of the vibrated sample cell. By varying the vibration parameters, the surface tension, and the density difference between the two phases via the temperature, it was found that the wavelength and the amplitude of the stationary profile are both increasing functions of the frequency and of the amplitude of the vibration and that they are proportional to the capillary length. Our measurements are consistent with a model of inviscid and incompressible flow averaging the effect of the vibration over a period and leading to a Kelvin-Helmholtz-like instability mechanism due to the relative motion of the two fluids.