Experimental and Numerical Simulation of Heat Transfer in an Impact Synthetic Jet

Local heat transfer in an synthetic impact jet on a flat plate has been experimentally and numerically studied with a varying Reynolds number and pulse frequency. The thermal characteristics at the stagnation point on the surface of an obstacle have been studied: instantaneous and fluctuation values of the heat flux rate and the spectrum of heat flux fluctuations. Measurements and numerical calculations of the local heat transfer coefficient are carried out under varying the distance to the plate and the amplitude and frequency of synthetic jet fluctuations. Regions with maximum instantaneous values of the heat flux and heat transfer coefficient are determined for local heat transfer values. The maximum value of the time-averaged Nusselt number is observed at the stagnation point of the synthetic impact jet for all considered distances to the obstacle surface. A qualitatively similar distribution of the Nusselt number over the radial coordinate corresponds to those for nonsteady and steady impact jets. The largest and smallest values of the averaged heat flux at the stagnation point were obtained at H/d = 4 and 1, respectively.