
Accession Number : ADA300740
Title : Direct Numerical Simulations of Separated and SeparatedReattaching Flows on Massively Parallel Processing Computers.
Descriptive Note : Master's thesis,
Corporate Author : ILLINOIS UNIV AT URBANA
Personal Author(s) : Najjar, Fady M.
PDF Url : ADA300740
Report Date : APR 1994
Pagination or Media Count : 323
Abstract : Direct numerical simulations of separatedreattaching and separated flows have been performed on massively parallel processing computers. Two basic geometrical configurations have been studied: the separatedreattaching flow past a normal flat plate with an attached downstream splitter plate and the separated flow past a flat plate held normal to a uniform stream. A highorder finitedifference formulation on collocated grids has been developed to perform unsteady fluid flow simulations in rectangular geometries. The numerical procedure is based on a fifthorder upwindbiased scheme for the convective terms and a fourthorder accurate stencil for the diffusive terms. A direct solver based on eigenvalue decomposition has been developed for the pressurePoisson equation. A mixed Fourier spectral /finite difference formulation is used for the spanwise discretization, and a dataparallel algorithm has been developed for the CM5. The performance of the algorithm has been evaluated on various grid sizes in model flow problems and for different partition sizes. The characteristics of the separatedreattaching flow have been investigated through twodimensional simulations in the steady and unsteady regimes. The shedding mechanism is characterized by two major modes at Re = 250 and a single mode at Re = 375 and 500. Further, the instability of the separated shear layer is found to be consistent with inviscid theory. For the twodimensional study of the separated flow past a normal flat plate, the timemean flow quantities are observed to be overestimated compared to the experiments. The timemean drag coefficient is also overpredicted by a factor of up to 2. This is attributed to the high coherence of the vortices predicted by the twodimensional simulations
Descriptors : *MATHEMATICAL MODELS, *PARALLEL PROCESSING, *FLOW SEPARATION, SHEAR PROPERTIES, ALGORITHMS, COMPUTERIZED SIMULATION, COMPUTATIONS, SIZES(DIMENSIONS), INTERACTIONS, COMPUTERS, LAYERS, FORMULATIONS, GRIDS, NUMERICAL ANALYSIS, COHERENCE, CONVECTION, VORTICES, FINITE DIFFERENCE THEORY, PLATES, RECTANGULAR BODIES, WAKE, TWO DIMENSIONAL FLOW, UNSTEADY FLOW, NUMERICAL METHODS AND PROCEDURES, INVISCID FLOW, FLUID FLOW.
Subject Categories : Operations Research
Fluid Mechanics
Distribution Statement : APPROVED FOR PUBLIC RELEASE