NUMERICAL INVESTIGATION ON WAKE OF CYLINDER COVERED WITH ELECTRO-MAGNETIC ACTUATOR
包覆电磁场激活板的圆柱尾迹的数值研究

It is possible to control the flow in the electrolyte solution by Lorentz force generated by the suitably chosen magnetic and electric fields. Based on the vorticity/stream function formulation of the Navier-Stokes equations considering the electro-magnetic body force, i.e. Lorentz force, in the exponential-polar coordinates, the numerical investigations on the wake of a cylinder, covered with electro-magnetic actuators, in weak electrolyte solution in Re=150 were performed by means of an Alternative-Direction Implicit algorithm for the vorticity transport equation and a Fast Fourier Transform algorithm for the stream function equation with the accuracy of second order in space and first order in time.The interaction parameter N is defined as the ratio of the electro-magnetic force to the inertia force. The control of cylinder wake by actuators with the constant N is called open loop control. It has been shown from the calculated results in this case, that the efficiency of the localized Lorentz force in controlling the flow is similar to that of the Lorentz force distributed over the whole surface. The vortex shedding will completely disappears, when the actuators only are set on areas centered around separation points in the rear surface of the cylinder.The interaction parameter N can be varied with some partial flow information on the cylinder surface in the control procedures, called closed loop control. For example, N can be modified to make either zero pressure drag, CP_(d) = 0, or zero total drag, C_(d) = 0. According to calculated results, the closed loop control strategy has a significant effect on the control of a cylinder wake. The values of N oscillates at the beginning stage and then tends to steady.It is obvious that closed and localized open loop electro-magnetic control not only are able to manipulate wake flow, but also offer the advantage of requiring a significantly reduced amount of control power.