Experiments on the Stability of Stratified Shear Flows

Abstract

Some experiments are described in which a shear flow is developed in a stratified brine solution contained in a long, closed tube of rectangular cross section. The fluid motion is produced by tilting the tube from an initial horizontal position, and the flow thus generated is found to be uniformly accelerating and easily expressed in terms of the initial density profile in the tube until disrupted by instability. (The details of the method are given in an earlier paper.) The particular case of a diffuse interface between two homogeneous layers of different densities that move with equal and opposite speeds is discussed in some detail, and the transition to turbulence is described. The transition is characterized by the formation of waves that develop into rolls of a very beautiful form. Measurements at the onset of the wave motion are compared with theoretical predictions.