| Boundary layer control on a circular cylindrical body through oscillating Lorentz forcing is studied by means of numerical simulation of the vorticity-stream function formulation of the Navier-Stokes equations. The model problem considers axisymmetric seawater flow along an infinite cylinder controlled by an idealized radially directed Lorentz force oscillating spatially and temporally. Under optimum forcing parameters, it is shown that sustainable Lorentz induced vortex rings can travel along the cylinder at a speed equivalent to the phase speed of forcing. Wall stress is shown to locally change sign in the region adjacent to the vortex, considerably decreasing net viscous drag. Adverse flow behaviors are revealed as a result of studying the effects of the Reynolds numbers, strength of the Lorentz force, and phase speed of forcing for boundary layer control. Adverse flow behaviors include complex vortex configurations found for suboptimal forcing resulting in a considerable increase in wall stress. |
