Planar measurements of the full threedimensional scalar dissipation rate in gasphase turbulent flows
Abstract
A simultaneous planar Rayleigh scattering and planar laserinduced fluorescence (PLIF) technique is described which allows planar measurement of the full threedimensional scalar gradient, ∇C (x, t), and scalar energy dissipation rate, χ≡D ∇C.∇C, in gasphase turbulent flows. The conserved scalar used is the jet fluid concentration, where the jet consists of propane and seeded acetone. The propane serves as the primary Rayleigh scattering medium, while the acetone is used for fluorescence. For a given amount of available laser energy, this planar Rayleigh scattering/PLIF technique yields much higher signals levels than would, for example, a twoplane Rayleigh scattering technique. By applying the current technique to a single spatial plane, the errors incurred in measuring a spatial derivative across distinct planes are quantified. The errors are found to be well described by a random distribution, and the magnitude of these errors is found to be smaller than the magnitude of significant events in the true scalar gradient fields. Sample results for the fields of the threedimensional scalar gradient and scalar energy dissipation in a planar turbulent jet, with outer scale Reynolds numbers between 3200 and 8400, are shown, demonstrating the applicability of these measurements to analyses of the fine scale mixing in turbulent flows. The application of these measurements to determination of the scaling properties of the dissipation rate is also discussed.
 Publication:

Experiments in Fluids
 Pub Date:
 1999
 Bibcode:
 1999ExFl...27..507S