VORTEX-SCALAR ELEMENT CALCULATIONS OF A CONFINED CHEMICALLY REACTING MIXING LAYER

THIS PROPOSAL DESCRIBES A COMPUTATIONAL EFFORT, BASED ON A LAGRANGIAN "VORTEX-SCALAR ELEMENT" METHOD, FOR THE SIMULATION OF A TIME-DEPENDENT MIXING LAYER UNDER BOTH NONREACTING AND NONPREMIXED REACTING CONDITIONS. THE METHOD REPRESENTS VORTICITY AND SCALARS (CONCENTRATIONS AND TEMPERATURE) BY "VORTEX" AND "SCALAR" ELEMENTS, RESPECTIVELY, AND HAS THE ADVANTAGE THAT HIGH REYNOLDS NUMBER FLOWS CAN BE SIMULATED ACCURATELY. IN PHASE I, SIMULATIONS WILL BE PERFORMED FOR A TWO-DIMENSIONAL, SPATIALLY DEVELOPING MIXING LAYER. THE FOLLOWING PHYSICAL PHENOMENA WILL BE CONSIDERED: (1) THE ASYMMETRIC MIXING MECHANISM IN A NONREACTING MIXING LAYER; (2) INTERACTIONS BETWEEN LARGE COHERENT STRUCTURES AND FINITE RATE CHEMICAL REACTIONS IN A DILUTE REACTING MIXING LAYER; AND (3) THE NONEQUILIBRIUM EFFECTS OF VARIABLE-TEMPERATURE CHEMICAL REACTIONS ON THE IGNITION AND EXTINCTION CHARACTERISTICS OF A DIFFUSION FLAME. IN PHASE II, A NEW SCHEME WILL BE IMPLEMENTED TO SOLVE THE SCALAR TRANSPORT EQUATIONS, AND THE THREE-DIMENSIONAL PROBLEM WILL BE STUDIED. THE SCALAR ELEMENTS WILL BE REPLACED BY "SCALAR GRADIENT ELEMENTS" FOR THE SOLUTION OF THE SCALAR TRANSPORT EQUATIONS. THIS WILL IMPROVE THE EFFICIENCY AND THE SPATIAL RESOLUTION OF THE NUMERICAL PROCEDURES SUBSTANTIALLY. NEXT, THREE-DIMENSIONAL CALCULATIONS BY TRACING "VORTEX FILAMENTS" WILL BE PERFORMED. SUCH SIMULATIONS WILL EXHIBIT THE EFFECTS OF THREE-DIMENSIONAL TURBULENCE MOTION ON THE CHEMICAL REACTIONS AND ALSO WILL DETERMINE THE RANGE OF VALIDITY OF RECENTLY DEVELOPED ADVANCED TURBULENCE MODELS FOR THE PREDICTION OF SUCH FLOWS.