An Experimental Investigation of Synthetic Jet in a Coflow Wake

A round synthetic jet issuing into a coow wake is investigated experimentally in this paper. The ow eld of the jet is measured using hot-wire anemometry. The spreading and decaying of the synthetic jet is studied after taking into account the eect of the wake velocities. The evolution of the synthetic jet is modeled much like a continuous turbulent jet in a co-ow. The model employs an integral formulation where the excess momentum ux is conserved, along with a spreading hypothesis that assumes that the rate of growth of the shear layer is proportional to the relative velocity between the dominant eddies in the jet and the surroundings. The characteristic velocity and length scales are derived from an equivalent top hat velocity prole. The jet in the far eld is observed to exhibit selfsimilar behavior as distinguished by the collapse of the excess mean velocity proles. The streamwise variation of centerline velocity show good agreement with the semi-empirical integral model. By verifying the theoretical model, it can be concluded that the jet decay is not aected by the presence of ambient coow. Additionally, the spreading of a synthetic jet would be decreased as the coow velocity increases. Finally, a stronger jet would be responsible for a faster velocity decay and an enhanced spreading for synthetic jet in coow wake.