Accession Number : ADA259934


Title :   Mixing in Gas Phase Turbulent Jets


Descriptive Note : Doctoral thesis


Corporate Author : CALIFORNIA INST OF TECH PASADENA


Personal Author(s) : Dowling, David R


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a259934.pdf


Report Date : Jan 1988


Pagination or Media Count : 269


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 Reynold's number while the local mixing rate in the inner part of the jet is not. The usual assumptions concerning isotropy and correlation of derivatives are found to lead to erroneous results for the probability density function of the scalar dissipation rate.


Descriptors :   *TURBULENT FLOW , *PHOTODETECTORS , *ARGON LASERS , *NOZZLE GAS FLOW , *JET MIXING FLOW , *JET FLOW , VELOCITY , DENSITY , DIAMETERS , LIGHT SCATTERING , MEASUREMENT , LASERS , TIME , RAYLEIGH SCATTERING , RESERVOIRS , EXITS , ANALOG TO DIGITAL CONVERTERS , MEAN , FLOW , MIXING , FLUIDS , DATA ACQUISITION , SPECTRA , PROBABILITY DENSITY FUNCTIONS , POWER SPECTRA , TEMPERATURE , SCATTERING , THESES , DISSIPATION


Subject Categories : Electrical and Electronic Equipment
      Statistics and Probability
      Optical Detection and Detectors
      Fluid Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE