Experiments have been performed in turbulent shear layers to measure the effects of Reynolds number on molecular mixing. The experiments extend the upper range of incompressible, chemically-reacting flow data from Re=1.6x10⁵ to 3.5x10⁵. This was recently extended to 7x10⁵, as part of a collaboration with M. Slessor (Slessor, Bond, and Dimotakis 1997). The experiments address an ambiguity in recent measurements of molecular mixing in compressible shear layers, whose difference from measurements in incompressible shear layers could have been due either to compressibility or Reynolds number effects. The current results, taken collectively with previous results, show that the decrease of mixing with increasing Reynolds number, first seen by Mungal, Hermanson, and Dimotakis (1985), continues to the Reynolds numbers studied, but suggest no further decrease in mixing. This conclusion must be tempered, however, by changes in initial boundary layers and acoustic environment with increasing flow velocity, and by possible compressibility effects at the highest Reynolds numbers (Re=7x10⁵) investigated.

References:

Bond, C. L., and Dimotakis, P. E., 1996 "Molecular mixing in high Reynolds number, subsonic, free shear layers," Fall Technical Meeting, Western States Section (Combustion Institute), 28--29 October 1996 (U. So. California), Paper 96F-099.

Mungal, M. G, Hermanson, J. C., and Dimotakis, P. E., 1985 "Reynolds Number Effects on Mixing and Combustion in a Reacting Shear Layer," AIAA J. 23(9), 1418--1423.

Slessor, M. D., Bond, C., and Dimotakis, P., 1997 "Chemical reaction studies in subsonic, low-compressibility free shear layers," GALCIT Technical Report FM97-12 (in preparation).