Computed and experimental interactions between eddy structure and dispersed particles in developing free shear layers

The interactive process between turbulent flow and dispersed phase particles is investigated, focusing on the mechanisms that appear to result in a reduction of local turbulent intensity and a corresponding reduction in wall heat transfer and subsequent wall erosion in turbulent solid propellant combustion flow. Computational simulations are applied and physical experiments specialized to a developing free shear layer over a rearward facing step and over a parallel splitter plate. The flow configuration evolves in a two-dimensional, steady, combustion and noncombustion turbulent free shear mixing region, with and without particle additives. The computational simulations combine three basic components: gas phase Navier-Stokes solutions, Lagrange particle field solutions and a Monte Carlo technique for the random encounters, forces and accelerations between the two fields. Attention is concentrated here on relatively large sized additive particles (of the order of tens of microns to 100 microns mean diameter). Their apparent influence in breaking up the larger, energy bearing eddy structures into smaller structures which are more readily dissipated is examined.