Modares Mechanical Engineering

Modares Mechanical Engineering

Experimental drag reduction by injection of air bubbles in a Couette-Taylor system and in turbulent Taylor vortex flow

Authors
Sistan and Baluchestan, Zahedan
Abstract
The effect of bubbles on frictional drag reduction has been studied experimentally using a vertical Taylor-Couette system. Air bubbles are injected into water flow at the bottom of the system. The flow between cylinders is a fully turbulent flow and Taylor vortices are formed in annulus gap. In these experiments, the variations range of rotational Reynolds number is 5000<=Re_w<=70000 . The variations of drag reduction in the presence of bubbles have been investigated by measuring the exerted torque on the inner cylinder. The results show that increasing rotational Reynolds number up to a certain amount leads to enhancement of bubbles effects on drag reduction while the effects are inversed for higher rotational Reynolds number. In this work, the acquired maximum drag reduction is about 5%.
Keywords