Manipulation of a round jet with electromagnetic flap actuators

A novel axisymmetric jet nozzle equipped with a row of miniature electromagnetic flap actuators on its circular lip is developed for active flow control. Each of the flaps fabricated by photolithography is independently driven according to a control signal supplied by a PC. The spatio-temporal flow structures of the controlled jet are studied through flow visualization and laser Doppler velocimetry (LDV) measurement. It is found that artificial disturbances generated by the flaps can modify the formation and evolution of large scale vortical structures significantly. When each half cluster of these flaps are driven out of phase, the jet clearly bifurcates into two branches and its mixing is markedly enhanced in the plane of bifurcation.