Turbulent shear-layer mixing at high Reynolds numbers: effects of inflow conditions

We report on the results from a set of incompressible, shear-layer flow exp eriments, at high Reynolds number (Re delta = rho Delta U delta(T)(x)/mu si milar or equal to 2 x 10(5)), in which the inflow conditions of shear-layer formation were varied (delta(T) is the temperature-rise thickness for chem ically-reacting shear layers). Both inert and chemically-reacting flows wer e investigated, the latter employing the (H-2+NO)/F-2 chemical system in th e kinetically-fast regime to measure molecular mixing. Inflow conditions we re varied by perturbing each, or both, boundary layers on the splitter plat e separating the two freestream flows, upstream of shear-layer formation. T he results of the chemically-reacting 'flip experiments' reveal that seemin gly small changes in inflow conditions can have a significant influence not only on the large-scale structure and shear-layer growth rate, as had been documented previously, but also on molecular mixing and chemical-product f ormation, far downstream of the inflow region.