Observations d'une instabilité convective apparaissant sous la forme de rouleaux sinueux dans un écoulement de Poiseuille–Rayleigh–Bénard

Abstract

A both experimental and numerical study of a mixed convective flow in a rectangular channel heated at the bottom and cooled at the top is reported. In such configuration, it is well known that for a Rayleigh number above a critical value and for sufficiently high Reynolds number, longitudinal counter-rotating rolls develop. A linear temporal stability analysis conducted in 1991 detected the onset of a wavy instability of the longitudinal rolls. In our study, experimental results and 3D direct simulations clearly show the development of the wavy pattern and point out the convective behaviour of this instability. To the knowledge of the authors, it is the first time that this instability is observed.