GRADUATE AERONAUTICAL LABORATORIES CALIFORNIA INSTITUTE OFTECHNOLOGY Mixing in High Schmidt Number Turbulent Jets

Approved for public release; distribution is unlimited I3. ABSTRACT (aximum200 words) This thesis is an experimental investigation of the passive scalar (species concentration) field in the far-field of round, axisymmetric, high Schmidt- inmber (liquid phase), turbulent jets issuing into a quiescent reservoir, by means of a quantitative laser-induced fluorescence technique. Single-point concentration measurements are made on the jet centerline, at axial locations from 100 to 305 nozzle diameters downstream, and Reynolds numbers of 3,000 to 102,000, yielding data with a resolved temporal dynamic range up to 2.5 x 10', and capturing as many as 504 large-scale structure passages. Findings include the following. Long-time statistics of the jet concentration converge slowly. The behavior of the jet varies with Reynolds number. The spectral slopes are examined, arid no constant-1 (Batchelor) spectral slope range is present. Rather, in the viscous region, the power spectra exhibit log-normal behavior, over a range of scales exceeding a factor of 40, in some cases. Mixing in the far-field is found to be susceptible to initial conditions. The plenum/nozzle geometry also influences the variance. Mixing in these jets differs from gas-phase, order unity Sc,jet mixing. Experimental considerations such as buoyancy and resolution are shown not to influenc