PREDICTIONS OF IMPACTING SONIC AND SUPERSONIC JETS

A mathematical model of sonic and supersonic jets, validated previousl y by the present authors for the prediction of moderately and highly u nderexpanded free jets, is used to simulate the nearfield structure of jets which impact a flat surface orthogonally, and its accuracy asses sed by comparing model predictions with experimental data available in the literature. For impacting, moderately underexpanded jets, results derived from the model are found to be in close agreement with data o n the location of both free jet shocks, and the stand-off shock formed adjacent to the impacted surface. In addition, the model provides rea sonable estimates of density within the free jet and stagnation region s of such flows, with the existence, or otherwise, of stagnation bubbl es being successfully predicted. Measurements of pressure occurring on the surface of the impacted plate, produced by the impingement of bot h sonic and supersonic jets, are also predicted with reasonable accura cy, although the decaying amplitude of spatially periodic pressure osc illations within the wall jet region of these flows is slightly overpr edicted in some cases.