Instabilities at the interface between miscible fluids under a horizontal oscillating forcing

Experiments were performed in order to study the instability at the interface between miscible fluids placed in a closed tank when submitted to a horizontal and sinusoidal oscillating forcing. For a given amplitude a, the frequency f was progressively increased untill a threshold frequency above which a stationnary relief can be observed in the reference frame of the tank. The difference of density involves an oscillating shear which lead to a Kelvin-Helmholtz type instability. An experimental stability curve was determined and confirms the physical mecanism. The capillar effects which could be expected at the interface between such fluids can be neglicted. (C) 2003 Academie des sciences. Publie par Editions scientifiques et medicales Elsevier SAS. Tons droits reserves.