Control mechanism of turbulent channel flow by spatially spanwise oscillating Lorentz force

Abstract

Turbulent channel flow control by using a spanwise oscillating Lorentz force with steady distributions has been investigated numerically via the pseudo-spectral method. The turbulent control and the drag reduction can be achieved by spanwise oscillating Lorentz forces with proper control parameters. The vortex generation is impacted in the controlled turbulent channel flow, and that only periodically well-organized streamwise vortexes are observed in the near-wall region of the turbulent channel flow. If the turbulent control is regarded as a process in which the turbulence flow is modulated by the induced flow, it has been shown that the induced flow dominants the modulated flow field when the turbulent flow is effectively controlled by the Lorentz force. Therefore, basic features of streamwise vortices in the controlled flow, such as configurations, distributions and its formations and annihilations, are related with the induced flow field and the Lorentz force distributions closely, based on which the mechanism of the turbulent control is elucidated finally.