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 experiments, at high Reynolds number (Reδ≡ρΔUδT(x)/ μ≃2×105), in which the inflow conditions of shear-layer formation were varied (δT is the temperature-rise thickness for chemically-reacting shear layers). Both inert and chemically-reacting flows were investigated, the latter employing the (H2+NO)/F2 chemical system in the kinetically-fast regime to measure molecular mixing. Inflow conditions were varied by perturbing each, or both, boundary layers on the splitter plate separating the two freestream flows, upstream of shear-layer formation. The results of the chemically-reacting ‘flip experiments’ reveal that seemingly 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 formation, far downstream of the inflow region.