Abstract
The stability of the hyperbolic flow obtained in Taylor's four rolls mill is investigated experimentally. The dimensionless parameter characterising the flow appears to be the internal Reynolds number based on the velocity gradient and on the gap between the rollers. Below a threshold value of Rec = 17 the hyperbolic flow is found to be stable. At the threshold it destabilises (by a supercritical bifurcation) to form an array of counter-rotating vortices aligned along the stretching direction. Near the threshold, the transverse velocity profiles of these vortices are in excellent agreement with those predicted by the theory of Kerr and Dold (1994) in the case of an infinite hyperbolic flow. Finally, in the high Reynolds number regime, it turns out that the velocity gradient (the stretching) is systematically weaker inside the vortices than elsewhere. This shows experimentally the existence of a negative feedback of rotation on stretching.