Direct Numerical Simulation of Turbulent Friction Drag Reduction by Traveling Wave-Like Blowing Using Plasma Actuators

Abstract

We numerically investigated the effects of friction drag reduction and energy gain by traveling wave-like blowing using plasma actuators arrayed on channel walls. Wall-normal flow is induced by opposed arrangement of plasma actuators. We used Shyy et al.’s model [1] to compute the body force of plasma actuators, which is added to the Navier-Stokes equation. With this model, the body force distribution is simplified as compared to the actual one, which is quite complicated. We perform direct numerical simulation under several parameter sets: the wavenumber, the amplitude, and the phasespeed of body forces. The obtained maximum friction drag reduction rate is 37% as compared to the uncontrolled case. Under the same phase speed and amplitude of body force, the friction drag is found to be reduced more with larger wavenumber. Under the same phase speed and wavenumber, the friction drag reduction is found to be larger with stronger body force. In the drag reducing cases, formation of spanwise vortices leads to reduction of the Reynolds sheer stress near the wall as well as the friction drag. Although net energy saving is acheived in some parameter sets, it is not achieved in most cases. This means that the reduced pumping power is generally smaller than the power input of plasma actuators.