Electromagnetic Control Of Low Reynolds Number Flow Around A Cylinder

The control of flow past a circular cylinder with electrodes and magnetics mountedalternately on its forces had been investigated both experimentally and numerically.With the use of a circular cylinder covered with electrodes and magnetics in alow-conducting electrolytic flow, the control effect of Lorentz force on the cylinder hadbeen investigated experimentally, and based on the Maxwell equations in the electro-magnetic fields, the Lorentz forces induced by the actuator with cylindrical shape in amoving low-conducting electrolyte, were calculated numerically, the distribution ofLorentz force and its control effect on cylinder wake had also been simulated numericallyin a moving low-conducting electrolyte. The influences of actuator width to the distributionof electro-magnetic fields, Lorentz force, flow field, and the direct effect of the force of thecylinder, indirect effect of the force by changing the flow, and holistic effect of the forcemodified by the Lorentz force were simulated and discussed.After our experimental and numerical investigations, some useful conclusions wereobtained as follows:The distribution of the voltage, the electro-magnetic fields are periodic alongthespanwise direction, and the Lorentz forces attenuate exponentially along the normaldirection of cylinder surface. At the middle of every actuator, the Lorentz force gets itsminimum value, and is maximum at the boundary. On the other hand, the wider of theactuator, the smaller of average Lorentz force value, and also the slower of its attenuation,which results in a large penetration depth, and vice versa.The electromagnetic body forces, which caused by the electromagnetic field canchange the cylinder boundary layer structure and suppress the boundary layer separation.However, the control effect of electromagnetic force is different with different value anddifferent actuator width. When Lorentz force is small, the separation points on the cylindersurface will be moved rearward, but it cannot be suppressed completely, however, at thisvalue, a narrow actuator gets better suppression effect. When the Lorentz force becomelarge, the flow separation can be suppressed completely and no vortex street occurs behindthe cylinder. In this case, both the wide and narrow actuators can suppress the cylinderwake successfully.