Book Description

The interference phenomenon occurring when a subsonic turbulent jet exhausts normally from a large flat plate into a low speed crossflow was experimentally investigated in the Georgia Tech nine foot wind tunnel. Static pressures were measured on the surface around the jet. In the region off the surface, including the jet plume, wake and surrounding areas, the average total and static pressures and the average velocity magnitudes and directions were determined. Three jet exit configurations were studied, one circular and two slot-shaped with width to length ratios of 0.3 and 3.4. All have the same exit area. The effective jet to cross-flow velocity ratio was varied, for each of the exit configurations, over the range 4.0 to 12.0. Analysis of the data indicates that the pressure distributions induced on the surface are a combined result of the jet's blocking and entraining effects on the cross flow with entrainment becoming the more dominant of the two as the effective velocity ratio is increased. This relative dominance brings about an attenuation of total interference lift loss (when computed as a fraction of gross thrust) primarily by causing a rise in the low pressures in the wake region as the effective velocity ratio increases. When the effective velocity ratio is held fixed, the total interference lift loss increases with increasing width to length ratio of the jet exit. (Author).