AN EXPERIMENTAL-STUDY OF THE FLOW EMERGING FROM POROUS WALLS

The fluid mechanics of air flow exiting from porous materials is inves tigated. Porous walls with filter ratings differing by about three ord ers of magnitude are studied. The flow behavior is investigated for it s spatial and temporal stability. The measurements show that coalescen ce effects cause jet development which gives rise to a stable, spatial velocity nonuniformity termed pseudo-turbulence. Beyond a critical me an velocity, the pseudo-turbulence shows a leveling trend and the flow exhibits jets whose dimensions are independent of wall porosity and p rovide a unique length scale for this type of flow field (almost-equal -to 1 mm). A correlation is developed to predict the onset of fully de veloped jets. The impact of using porous wall materials in cold flow s olid rocket motor testing is addressed.