NUMERICAL-SIMULATION OF VORTEX-SHEDDING PHENOMENON IN A CHANNEL WITH FLOW-INDUCED THROUGH POROUS WALL

Segmented solid propellant rocket motors tend to develop unpredicted p ressure and thrust oscillations that could be attributed to a periodic phenomenon. An experimental and numerical assessment of the stability of a solid propellant motor was conducted. This numerical computation was based on an experimental study carried out on a cold-flow, reduce d-scale, bidimensional duct with a complex internal geometry (obstacle s, outflowing cavities, submerged nozzle). The objectives of our study are to characterize the internal flow (mean, fluctuating induced by i njection through a porous wall and the shear layer created at the top of the second obstacle. The code employed solves the unsteady, compres sible two-dimensional (2-D) Navier-Stokes equations in a laminar regim e by a predictor-corrector MacCormack scheme. Three grids are develope d for the evaluation while respecting the complexity of the internal g eometry. The results obtained allow us to separate the flow into two z ones: one, laminar, upstream of the obstacle; the other, disturbed, do wnstream, in which vortex structures develop. The phenomena of instabi lities (vortex-shedding, pairing) are in accordance with the first two acoustic longitudinal modes of the chamber. Last, the numerical compu tations are discussed and systematically compared with the experimenta l results. (C) 1997 by Elsevier Science Inc.