Drag Reduction in Turbulent Compressible Channel Flows Using Spanwise Velocity Waves

Numerical simulations in compressible turbulent channel flows are carried out by applying the active control technique of spanwise velocity waves traveling in streamwise direction. The sinusoidal waves traveling in upstream direction are selected for the present study. For Mach number \(Ma = 1.5\) and bulk Reynolds number \(Re_b = 3000\) , the effects of varying the amplitude of control velocity while keeping other parameters constant are analyzed with the aim to achieve maximum turbulent drag reduction. The application of this active control technique for all the amplitudes studied successfully modifies the near-wall structures by reducing high-speed streaks and vortical structures. The maximum turbulent drag reduction, \(\texttt {DR = 37.01}\) % is observed at threshold amplitude \(Amp = 1.5\) for a selected wave number \(\kappa \) and oscillation frequency \(\omega \) . The spanwise vorticity near the walls is suppressed and hence, the turbulent drag produced by eddies is reduced as well.