Experimental and Computational Investigation of Supersonic Impinging Jets

The results of an experimental and computational study of a moderately underexpanded axisymmetric supersonicjetissuingfroma convergingnozzleand impingingonagroundplanearepresented.Thegoalofthisworkisto develop a better understanding oftheimpinging jet e owe eld, which is of signie cantpracticalinterestbecause of its presence in short takeoff and vertical landing (STOVL)aircraft during hover as well as in other aerospace-related and industrial applications. Theexperimental measurementsinclude e ow visualization, surface-pressuredistributions,and velocitye elddataobtained using particleimagevelocimetry (PIV).Theexperimentaldata,especially the velocity e eld measurements, were used to verify theaccuracy of computational predictions. Computational results obtained using two differentturbulencemodels produced almost identical results. Comparisons with experimental results reveal that both models capture the signie cant features of this complex e ow and were in remarkably good agreement with the experimental data for the primary test case. The experiments and computations both revealed the presence of the impingement zone stagnation bubble, which contains low velocity recirculating e ow. Other features, including the complex shock structure and the high-speed radial wall jet, were also found to be very similar. The ability to measure and predictaccurately theimpinging jetbehavior, especially neartheground plane, is critical because these are regions with very high mean shear, thermal loads, and unsteady pressure forces, which contribute directly to the problem of ground erosion in STOVL applications.