Dynamics and Control of an Isolated Jet in Crossflow

Abstract

Experimental results from a systematic exploration of the dynamics and control of large-scale, organized structures in an isolated, circular jet issuing into a uniform crosse ow with a jet-to-crosse ow velocity (or blowing) ratio of 6 are presented. Surveys of the unsteady e owe eld were conducted using a single sensor hot-e lm probe, and the instantaneous and time-averaged scalar e elds were explored using Mie scattering-based e ow visualization. A spinning mechanical valve was used to modulate the jet e ow with a single frequency. The forced e ow response illustrates the e ow receptivity to high frequencies near the jet exit (associated with the jet instabilities) and to low frequencies farther downstream (where the counter-rotating vortex pair dynamics are dominant). Open-loop forcing in a jet Strouhal number around SrD =0.1 was recognized and demonstrated to be effective in organizing unsteadiness and enhancing mixing and entrainment in the e owe eld. Measurements of the time-averaged velocity and scalare eldsareusedtodemonstrateincreasedmassentrainmentandmixingasaresultoftheunsteady forcing.