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 characteristics of modulated wall turbulence and turbulent drag reduction. In the simulations, the effect of surfactant solution was represented by the modified Bird-Carreau model for shear viscosity. Our simulations reproduced experimental features of turbulent flow of surfactant solution. One result was a drag reduction rate of 37%, which is in the range of low drag reduction. Considering instantaneous structures and turbulence statistics, our scale analysis found that modulation of turbulent flow of surfactant solution for the Newtonian fluid could be generally normalized with the local variable viscosity. Some additional corrections are, however, needed to apply this to predicting the dissipation rate, which the local viscosity affects directly in turbulent flow.

Keywords

• surfactant solution
• wall turbulence
• drag reduction
• non-newtonian fluid
• direct numerical simulation