Numerical study of frictional drag reduction using micro-bubbles in a vertical Couette-Taylor system

Abstract

In this work, we numerically study the reduction of frictional drag in a vertical Couette-Taylor system by using micro-bubbles. The silicon flow is in the annular gap between two concentric cylinders as the internal cylinder is rotating while the outer cylinder is stationary. Taylor vortices are formed between the cylinders and the rotational Reynolds number also varies from 700 to 4500. The carrier flow is silicone while air bubbles are constantly injected into the carrier phase at the bottom of cylinders and rise through the flow. By employing a discrete phase model and Euler-Lagrange approach, we investigate a two-phase turbulent flow. In this way, we study the distribution of the bubbles through the flow, which is acquired using numerical modeling. Our numerical results are in good agreement with the experimentally reported data for different values of Reynolds numbers. We also investigate the effect of injected air with a constant flow rate on the skin friction drag and on the drag coefficient ratio. Our numerical results illustrate a reduction of drag about 36% when microbubbles are injected into the system. This reduction can be achieved by the effect of the bubbles on the density of the fluid and transformed momentum.