A study of flows behind bluff bodies immersed in a sheared flow

This study includes three experiments. In the first experiment, a cylinder, three triangular rods, and a cylinder with a splitter plate were observed in a water tunnel under both sheared and uniform flow conditions. The tests illustrated the flows behind the bluff bodies. In the second experiment, three trace gases and three models were used in a wind tunnel under sheared flow conditions. The trace gas tests were conducted to deter mine the cause for the decrease of percent concentration in the spanwise direction as the Mach number increased. The third experiment was also conducted in the wind tunnel. Its objective was to observe the presence (or absence) of negative entropy spots behind bodies other than the previously tested cylinder.

The water tunnel experiments showed spanwise flow behind the cylinder. At the same water speeds, spanwise flow was found behind neither the triangular model nor the cylinder with the splitter plate. The trace gas experiments showed that the decrease of gas concentration was due to diffusion of the gases in the streamwise direction. No spanwise flow was observed behind the triangular model in the trace gas experiments. In the entropy tests, the triangular model produced no negative entropy data. From the three experiments, it was concluded that the local negative entropies behind a bluff body are related to the spanwise transport.