Pulsed jets in cross-flow

Water tunnel flow visualization measurements and a simplified analysis of pulsed jet flow are described, and flow properties related to nonsteady pulsating jet in a uniform cross-flow are investigated. The jet was installed on a false floor which could be used to provide a known boundary layer at the jet location. The jet was issued perpendicular to the floor and the cross-flow, which was visualized using the common dye technique. The vortex rings, at low frequency, penetrate into the cross-flow to a height significantly greater than for the same jet pulsed at high frequencies or for the steady jet. The trajectory of the vortex rings that are formed as a result of full jet pulsation is found to depend on the ratio of the cross-flow velocity to the vortex ring's self-induced translational velocity and the pulsation frequency. With proper design of the pulsation mechanism, a technique to control the vortex rings' penetration in a cross-flow may be implemented.