Development of flow field when a symmetrical underexpanded sonic jet impinges on a flat plate

Abstract

A differencing scheme known as the ‘Fluid-in-Cell’ method has been used in the numerical simulation of a choked jet of air impinging on a flat plate. Before sonic conditions are applied at the nozzle exit, the field of interest is at rest at the ambient pressure and temperature. The instantaneous application of sonic conditions at the nozzle exit is tantamount to the sudden appearance of a normal shock wave whose strength is determined by the experimental conditions.The results of the simulation describe the decay of the initial shock wave and its reflection at the plate; the formation of a second shock wave and its merging with the reflected shock giving rise to a detached shock wave which oscillates; and the growth and subsequent motion of a toroidal vortex that is generated between this shock wave and the plate. The results show clearly how the flow field which has been observed in physical experiments under stable operating conditions is developed.

An experimental study of the oscillatory flow structure of tone-producing supersonic impinging jets

“…The studies by Donaldson & Snedeker (1971), Carling & Hunt (1974), Gummer & Hunt (1974) and Kalghatgi & Hunt (1976) reported the occurrence of recirculation zones for stable impinging jets, and the plate pressure measurements of Alvi & Iyer (1999) indicate the occurrence of recirculation zones for nozzle-to-plate spacings where Henderson (2002) found no tonal production. Recirculation zones were also observed in the unstable impinging jet experiments performed by Ginzburg et al (1970) and the numerical analysis of Iwamoto & Deckker (1981), although the numerical study was not carried to steady state so it was not possible to determine the final stability condition of the jet. Detailed digital particle image velocimetry (DPIV) studies and numerical models of the impinging region flow in the studies of Alvi, Ladd & Bower (2002) also reveal recirculation zones.…”

Studies on oblique impinging subsonic and sonic jets

“…They suggested an acoustics feedback mechanism, and a formula for the frequency of oscillations was derived. Iwamoto and Deckker (1981) applied the fluid-in-cell method to study the formation of the shock waves near the wall. Iwamoto (1990) presented experimental and numerical simulations on the flow pattern in the jet field on impingement.…”