Mechanism of drag reduction by spanwise oscillating lorentz force in turbulent channel flow

Numerical simulations and experiment research are bothcarried out to investigate the control of spanwise oscillating Lorentzforces on a turbulent channel flow. The variation of the streaks and theskin friction drag are obtained through the PIV system and the dragmeasurement system, respectively. The flow field in the near-wall region isshown through direct numerical simulations utilizing spectral method. Theexperiment results are consistent with the numerical simulation onesqualitatively, and both indicate that the streaks are tilted into thespanwise direction and the darg reduction utilizing spanwise oscillatingLorentz forces can be realized. The numerical simulation results reveal moredetails of the drag reduction mechanism which can be explained as thespanwise fluctuating vortices generated, from interaction between the induced longitudinal vortices and intrinsicturbulent flow in the near-wall region can make the longitudinalvortices tilted and oscillated to suppress the turbulent intensity andlead to drag reduction.