Plasma actuators for cylinder flow control and noise reduction

In this paper, the results of flow-control experiments using single dielectric barrier discharge plasma actuators to control flow separation and unsteady vortex shedding from a circular cylinder in crossitow are reported.T his work is motivated by the need to reduce landing gear noise for commercial transport aircraft via an effective streamlining created by the actuators. The experiments are performed at Re-D = 3.3 x 10(4). Using either steady or unsteady actuation, Karman shedding is totally eliminated, turbulence levels in the wake decrease significantly, and near-field sound pressure levels associated with shedding are reduced by 13.3 dB. In the case of unsteady plasma actuation, an actuation frequency of St(D) = 1 is found to be most effective. The unsteady actuation has the advantage that total suppression of shedding isachieved for a duty cycle of only 25 %. However, because unsteady actuation is associated with an unsteady body forc-e and produces a tone at the actuation frequency, steady actuation is more suitable for noise-conlrol applications.