CFD simulation of flow fields associated with high speed jet impingement on deflectors

Computational Fluid Dynamics is used to analyze the formation of under-expanded jets and to investigate the three-dimensional flow field associated with the impingement of free jets onto stationary deflectors. This investigation was performed to develop a verified modeling ability for such problems. Predictions were compared with the experimental results obtained by Donaldson and Snedeker [1]. Computational models for free and impinging jets were created according to the data provided in Ref. 1. Numerical results for each of the experiments performed in this benchmark report are presented.

Three different turbulent free jets produced by a simple convergent nozzle were analyzed. These include a subsonic jet with p₁/pâ =1 and M₁=0.57, a moderately under-expanded jet with p₁/pâ =1.42 and M₁=1, and a highly under-expanded jet with p₁/pâ =3.57 and M₁=1. The reflecting shocks associated with the moderately under-expanded jet as well as the shock disk associated with the highly under-expanded jet were fully resolved. Velocity profile data predicted at locations downstream of the nozzle exit agreed very well with the experimental results.

The impingement of a moderately under-expanded jet with p₁/pâ =1.42 and M₁=1 was also investigated. The interaction of the high speed jet with circular flat plates at angles of 60° and 45° relative to the center axis of the jet are presented. Wall jet velocity profiles on the surface of the flat plate are fully resolved and compare well with experimental results. The CFD solver controls and method used to obtain these results are summarized and justified.