Measurements of the three-dimensional scalar dissipation rate field in gas-phase planar turbulent jets

Simultaneous, planar Rayleigh scattering and laser induced fluorescence yields 3D scalar and scalar dissipation rate field information in a planar turbulent jet. The conserved scalar used here is the jet fluid concentration, where the jet consists of propane, which serves as the Rayleigh scattering medium, seeded with acetone for fluorescence. The use of different imaging techniques for the two distinct spatial planes leads to higher signal levels than would, e.g., a two-plane Rayleigh scattering technique. Particular care must be taken to ensure pixel-to-pixel correspondence of the imaged planes. An important issue addressed is the degree to which the Rayleigh scattering and the acetone fluorescence individually and simultaneously mark the jet fluid concentration. Calculated values of the propane-air and acetone-air mass diffusivity suggest a negligible differential diffusion effect, borne out by measurements of the Rayleigh scattering and acetone fluorescence signals in a single spatial plane. This indicates that both techniques accurately measure the concentration of jet fluid. (Author)