Influence de l'acoustic streaming sur les instabilités affectant une couche de fluide chauffée latéralement

Abstract: The effect of acoustic streaming (more precisely the Eckart streaming) on the linear stability of a laterally heated fluid layer confined between two horizontal infinite walls (Hadley flow) has been studied. In the considered range of Prandtl number (), three types of instabilities prevail in the absence of acoustic streaming: two-dimensional stationary instabilities for low Prandtl numbers, and three-dimensional oscillatory and then stationary instabilities for higher Prandtl numbers. When an acoustic beam of width (normalized by the layer depth) is applied, the thresholds of the two-dimensional modes, which become oscillatory, increase with the acoustic intensity (monitored through the parameter A) before strongly decreasing to reach the pure acoustic streaming instability threshold. Concerning the three-dimensional instabilities, the thresholds of the oscillatory modes increase while those of the stationary modes strongly decrease. For , these evolutions induce the crossing of the critical curves of these two modes when A is increased, so that the oscillatory modes which are dominant for small values of A are replaced by the stationary modes for larger values of A. The position of the crossing depends on the width of the acoustic beam. To cite this article: W. Dridi et al., C. R. Mecanique 337 (2009). [Copyright &y& Elsevier]