Intermittent Turbulence in Plane and Circular Couette Flow

Abstract

Intermittent turbulence, the coexistence of laminar and turbulent flow1, is well known to exist in circular Couette flow when the two cylinders counter-rotate2. In particular, the turbulent and laminar regions may organize into the Spiral Turbulence pattern (alternating regions of laminar and turbulent flow which wrap around the axis of the cylinders to form a rotating spiral) or a V-shaped pattern (local spiral patterns of opposite helicity which connect to form V shaped regions). Evidence for the subcritical nature of the transition to Spiral Turbulence and V-shaped patterns is given by the large hysteresis in parameter space and by perturbation experiments3,4. The role of centrifugal instabilities in this state is not so clear although the interpenetrating spirals appear to initiate turbulent spots under certain circumstances. It is also thought that the boundedness in the azimuthal direction in circular Couette flow leads to the spiral or V-shaped intermittent patterns3,4. Because centrifugal instabilities and boundedness are absent in plane Couette flow, a comparison of intermittent turbulence in this case to circular Couette flow may help to further understand these patterns. We have recently completed a plane Couette flow apparatus and will present some preliminary results of experiments in which we have also observed intermittent turbulence.