Jet Interaction with a Primary Jet and an Array of Smaller Jets
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A combined experimental-numerical study of the jet interaction flowfield associated with sonic injection of a gas into a turbulent, high-speed crossflow (M = 4.0) was conducted with an innovative configuration for jet-thruster applications. This configuration consists of a sonic primary jet, flanked by arrays of smaller secondary sonic injectors that interact with the flowfield created by the primary jet. The mass flow from the small secondary jets ranged from 0.5-1% of that from the primary jet. Pressure sensitive paint was used to measure the pressure field acting on the surface. Forces and moments acting on the flat plate were quantified by integration of the pressure field. Schlieren photographs were used to analyze the main flow features generated by the jet interaction. The numerical solution used the Reynolds-averaged Navier-Stokes equations and Wilcox's k- turbulence model. The study showed that the main improvement of this configuration was a considerable reduction (by as much as 164%) in the generally undesirable nose-down pitching moment typical of jet-interaction flows. A secondary benefit was a small increase in the normal force by as much as 3%. These two effects were caused by reductions in both the size and intensity of the low-pressure region aft of the primary injector and, in some cases, by an increase in the extent and intensity of the separation region in front of the jet. The location of the secondary injector was not optimized here; it is believed that even larger improvements in the performance can be obtained by strategically locating the secondary injectors.
