Mass fluxes over(ρ^′ u^′, -) and over(ρ^′ υ^′, -) measured in a turbulentnonpremixed flame

Turbulent axial and radial mass fluxes over(ρ^′ u^′, -) and over(ρ^′ υ^′, -) have been measured throughout a high Reynolds number (Re_d=24,000) turbulent nonpremixed flame. In addition, the probability distributions of density and velocity have been measured, from which the means, higher moments and spatial gradients are generated. These measurements were made with a novel apparatus which combines laser velocimetry with laser Rayleigh scattering. Results indicate that the gradient diffusion assumption that is commonly made to model over(ρ^′ u^′, -) in first order closure theories is seldom obeyed throughout the flow. This is direct evidence of countergradient diffusion of density in a nonpremixed flame. The radial fluxes over(ρ^′ υ^′, -) are found to follow a gradient diffusion relation throughout the flow.