Accession Number : ADA259952


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


Descriptive Note : Annual rept. 1 Oct 1991-31 Sep 1992


Corporate Author : MICHIGAN UNIV ANN ARBOR GAS DYNAMICS LABS


Personal Author(s) : Dahm, Werner J


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a259952.pdf


Report Date : 10 Nov 1992


Pagination or Media Count : 34


Abstract : High resolution multi-dimensional imaging measurements were reported of the detailed structure of mixing and combustion processes in turbulent flows. These measurements are unique because they provide the first fully-resolved quantitative data on scalar dissipation rate field structure in turbulent reacting flows. These molecular mixing rate data were coupled with a two- parameter non-equilibrium reaction chemistry formulation to generate instantaneous maps of combustion species concentration and reaction rate fields in turbulent flames under varying degrees of chemical non-equilibrium. Results showed that the reaction zone structure transitioned smoothly from a thin layer- like structure to broad distributed reaction zones as the flame extinction limit was approached. Additionally, fully-resolved four-dimensional spatio-temporal imaging measurements were used to measure the larger scale topology of these scalar dissipation layers. Results showed that the distribution of layer separations is very nearly lognormal. This finding verified a recent analytical model of the multiplicative character of the repeated stretching and folding processes leading to this layer-like structure in the scalar dissipation fields in turbulent flows. This model, coupled with this two-parameter non-equilibrium reaction chemistry formulation, provides a simple approach for predicting the fine structure of molecular mixing and non-equilibrium reaction chemistry in turbulent combustion.


Descriptors :   *MEASUREMENT , *TURBULENT FLOW , *HIGH RESOLUTION , *MIXING , *CHEMICAL REACTIONS , EXTINCTION , MODELS , REACTION KINETICS , MOLECULAR STATES , DISTRIBUTION , CHEMICALS , FLAMES , MAPS , SEPARATION , IMAGES , SCALE , TOPOLOGY , COMBUSTION , CHEMISTRY , REGIONS , FINES , FOUR DIMENSIONAL , APPROACH , AIR BREATHING , FOLDING , LAYERS , PARAMETERS , FORMULATIONS , RESOLUTION , STRUCTURES , RATES , DISSIPATION


Subject Categories : Physical Chemistry
      Fluid Mechanics
      Air Breathing Engines(unconventional)
      Combustion and Ignition


Distribution Statement : APPROVED FOR PUBLIC RELEASE