Accession Number : ADA309483

Title :   High Resolution Measurements of Mixing and Reaction Processes in Turbulent Flows.

Descriptive Note : Final rept. 1 Oct 91-31 Dec 94,

Corporate Author : MICHIGAN UNIV ANN ARBOR

Personal Author(s) : Dahm, Werner J.

PDF Url : ADA309483

Report Date : 25 JAN 1995

Pagination or Media Count : 148

Abstract : Fully-resolved, two-, three-, and four-dimensional, spatio-temporal imaging measurements of the fine structure of conserved scalar mixing in turbulent flows are being used to identify new insights into molecular mixing and develop practical models for turbulent combustion. During the past year, the high wavenumber part of the scalar mixing spectrum has been measured and appears to confirm the Batchelor model. However the cutoff wavenumber is found to lie significantly lower than classical theory suggests We have also obtained the first measurements of the distribution of dissipation layer separations in turbulent flows. These results show a surpnsingly simple and potentially insightful -3 power law scaling for scalar mixing that has not yet been explained. A new strained dissipation and reaction layer (SDRL) model has been developed that relates the chemical state of nonequilibrium reaction chemistry to the mixing state of one or more conserved scalar fields. We have coupled this model with our high resolution Rayleigh imaging measurements to predict combustion species concentration and reaction rate fields in turbulent reacting flows. Results from this model show striking agreement with direct species imaging measurements in turbulent combustion, and allow access to species that cannot be measured directly. This new physically-based formulation appears to unify the previous 'flamelet' and 'distributed' reaction models within a single model capable of treating even deep nonequilibrium combustion.

Descriptors :   *TURBULENT FLOW, *COMBUSTION STABILITY, *SHEAR FLOW, MATHEMATICAL MODELS, COMPUTERIZED SIMULATION, IMAGE PROCESSING, REACTION KINETICS, LASER INDUCED FLUORESCENCE, REACTION TIME, DISSIPATION, TURBULENCE, OPTICAL IMAGES, VORTICES, FLOW VISUALIZATION, HIGH RESOLUTION, PROBABILITY DENSITY FUNCTIONS, FLOW FIELDS, DATA ACQUISITION, MOLECULE MOLECULE INTERACTIONS, NONEQUILIBRIUM FLOW, FLAME PROPAGATION, FLOW SEPARATION, PRESSURE DISTRIBUTION, REYNOLDS NUMBER, CONCENTRATION(CHEMISTRY), BOUNDARY LAYER FLOW, HIGH SPEED PHOTOGRAPHY, JET MIXING FLOW, TURBULENT DIFFUSION.

Subject Categories : Fluid Mechanics
      Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE