UC Davis

This paper reports on computations related to a turbulent jet impinging on a flat surface. The goal was to assess the efficiency of alternative methods for enhancing the heat-transfer rates at the target wall. Three methods were considered, all of which involved the manipulation of the jet flow at exit. These were the imposition of a tangential component of motion simulating the generation of swirl by guide vanes, the forced excitation of the mean flow at predetermined amplitude and frequency, and by the placement of a cylinder across the flow from which vortex shedding occurred. The computations were performed using Large-Eddy Simulations and the results compared with experimental data wherever available. It was found that the selection of active excitation frequency plays an important role in terms of enhancement of heat transfer. On the other hand, the passive excitation of the jet by introducing inserts in the flow causes high pressure drop while the introduction of swirl does not always bring about an appreciable enhancement in the heat transfer rates.