Experimental investigations of taylor-couette flow using PIV and electrochemical techniques

Abstract

The Taylor-Couette flow is an axisymmetric, sheared, and azimuthal flow. It holds a primary site in the history of fluid dynamics. Several works have been devoted to study this problem. Despite the fact that it is very, old, the problem of Taylor-Couette flow has received renewed interests in the past years. This renaissance is due to its high instability and the fact that it is particularly favorable to the rigorous mathematical analysis due to infinitesimal disturbances. The goal of this work is to provide an experimental study characterizing the Taylor-Couette instabilities in terms of interactions between vortices and wall. An experimental setup with a rotating inner cylinder and a fixed external cylinder was performed to study the flow at the gap between these two latters. Different types of movements imposed on mobile inner cylinder are available: cylinder oscillating, abrupt, or gradual disturbance. An axial flow was superimposed on the main flow of the Couette-Taylor. A qualitative study is firstly presented consisting of the visualization of the flow with the aim to draw the topology of the developed instabilities. Thus the different flow regimes conditioned by the dimensionless Taylor number are defined. The effect of superposition of an axial flow is shown. Experimental PIV measurements are then devoted to characterize the unsteady dynamics of the Taylor-Couette flow. Velocity and vorticity are investigated, and Γ2 criterion is used to locate the vortex. In the other hand, electrochemical method is used and synchronized with PIV technique to determine the velocity parietal gradient. This technique allowed studying the vortex-wall interaction using response of single and triple probe and PIV.