IV-2

M. Rabaud, L. Meignin and P. Gondret

F. A. S. T. Orsay

Abstract

We study the shape of an interface between a gas and a liquid in a Hele-Shaw. For large enough velocity of the gas flowing above the liquid, the interface becomes unstable and waves appear. We analyzed experimentally and theoretically this instability taking into account the strong viscous term imposed by the geometry. Close to threshold the instability is found to be of a convective type whereas it rapidly becomes absolute above a second threshold. For still larger flow rats localized structures interact and waves break and drops and a diphasic flow forms.