Direct Numerical Simulation of Drag Reduction and Heat Transfer Enhancement by Wall Oscillation in Turbulent Concentric Annular Pipe Flow

Abstract

In fluid engineering, the reduction of the skin-friction drag and the enhancement of the heat transfer are of importance in turbulent flows. In the present study, we made direct numerical simulations of the concentric annular turbulent pipe flow controlled by the wall oscillation control technique for the skin-friction reduction and heat transfer enhancement. The concentric annular pipe is widely used, and we expected to obtain the control effect by using the different radius of the inner and outer cylinders. Two types of control methods are shown: the wall oscillation technique and the traveling wave-like wall oscillation. In the wall oscillation, the friction drag decreases at all the frequencies, and the similarity between momentum and heat transport is maintained. In the traveling wave, the wave speed significantly affects the friction drag and the heat transfer. In some cases, the dissimilarity between momentum and heat transport is also confirmed.