Mixing in Gas Phase Turbulent Jets

Citation

Dowling, David Russell (1988) Mixing in Gas Phase Turbulent Jets. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/9233-5476. https://resolver.caltech.edu/CaltechETD:etd-06132005-160404

Abstract

This work is an experimental investigation of the mixing of the nozzle fluid of a round, turbulent jet with the entrained reservoir fluid, using laser-Rayleigh scattering methods. The measurements, at Reynolds numbers of 5,000 and 16,000, cover the axial range from 20 to 90 jet exit diameters and resolve the full range of temporal and spatial concentration scales. The measured mean and rms values of the concentration, and the mean scalar dissipation rate, when estimated from the time derivative of concentration, are consistent with jet similarity laws. Concentration fluctuation power spectra are found to be self-similar along rays emanating from the virtual origin of the jet, and are consistent with the universal form of scalar spectra proposed by Gibson (1968 II). The probability density functions for the concentration, the time derivative of concentration, and the square of the time derivative of concentration, are compiled and are also found to be self-similar along rays. Features of the measured distributions and spectra are consistent with the existence of large-scale structures within the flow that span the local diameter of the jet's turbulent cone. On the centerline of the jet, the scaled probability density function of jet gas concentration is found to be almost independent of the Reynolds number while the local mixing rate in the inner part of jet is not. The usual assumptions concerning isotropy and correlation of derivatives are found to lead to erroneous results for the probablility density function of the scalar dissipation rate.

Thesis Files