Predicting Drag-Reducing Wall Turbulence of Surfactant Solution by Direct Numerical Simulation

Abstract

We performed direct numerical simulations (DNS) of turbulent channel flow of surfactant solution to investigate the characteristics of the modulated wall turbulence and the drag-reduction. In the simulations, the effect of the surfactant solution was represented by the modified Bird-Carreau model for the shear viscosity. By comparing with the experimental results, we confirmed that the features of turbulent flow of surfactant solution were reproduced. In fact, one of the results showed the drag reduction rate of 37% and is in the range of low drag reduction. Due to the scale analysis from a viewpoint of instantaneous structures as well as turbulence statistics, we found that the modulation of turbulent flow of surfactant solution from the case of the Newtonian fluid could be generally normalized with the local variable viscosity. Some additional corrections are, however, needed to apply to the prediction of the dissipation rate, which the local viscosity affects directly in turbulent flow. © 2012 The Japan Society of Mechanical Engineers.