Experiments on the transition to turbulence of the flow between a stationary and a rotating disk

Abstract

The goal of this experimental study is to describe the transition to turbulence of the flow between a rotating and a stationary disk. Our experimental apparatus consists of a rotating disk set in a cylindrical housing full of water. Visualizations that use a small amount of anisotropic reflective particles permit the description of the different instabilities which occur in the flow. Circular and spiral waves are observed when the layer of water is larger than the boundary layers of the disks (Batchelor velocity profiles). At higher rotation speed, turbulence arises by a complex mixing of these waves. On the contrary, when the boundary layers are merged, the basic flow is close to a torsionnal Couette flow. In this case, isolated spots or solitary waves are visualized. When the Reynolds number is further increased, turbulence occurs in this case by the progressive invasion of the whole flow by these structures. Finally, these observations are compiled in a transition diagram which gives for the first time a global and detailed view of the transition to turbulence of the flow between a rotating and a stationary disk.