Control of near-wall streamwise vortices using an electromagnetic force in a conducting fluid

Effects of electromagnetic forcing on the near-wall vortices are investigated by applying a uniform magnetic flux in a turbulent channel flow in the streamwise and spanwise directions, respectively. The electromagnetic force induced from the magnetic fluxes inhibits the motion induced by the streamwise vortices and reduces their strength, and thus drag is significantly reduced. The wall-normal and spanwise turbulence intensities and the Reynolds shear stress decrease with the increased magnetic flux in both directions. The streamwise turbulence intensity increases with the streamwise magnetic flux, whereas it decreases with the spanwise magnetic flux. It is also shown that the spanwise magnetic flux is much more effective than the streamwise magnetic flux in reducing the skin-friction drag in the turbulent channel flow.