Date of Award

Fall 1989

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Mechanical & Aerospace Engineering

Program/Concentration

Mechanical Engineering

Committee Director

Oktay Baysal

Committee Member

Robert E. Smith

Committee Member

Surendra N. Tiwari

Call Number for Print

Special Collections; LD4331.E56L47

Abstract

Computing the flow fields about three-dimensional complex configurations accurately becomes a difficult task, if it is attempted to generate a single, body fitted grid with proper clustering. The domain decomposition methods, which divide the computational domain into less complex subdomains, are extensively used to decrease the grid generation workload. A domain decomposition technique also allows the use of different solution methods for different subdomains. The objective of this work is to develop a domain decomposition method via overlapping/embedding the component grids, which is to be used by upwind, multigrid, finite volume solution algorithms. A computer code, given the name MaGGiE, (Multi-Geometry Grid Embedder), is developed to meet this objective. MaGGiE takes independently generated component grids as input, and automatically constructs the composite mesh and interpolation data, which can be used by the finite volume solution methods with or without multigrid convergence acceleration. Six demonstrative examples, showing various aspects of the overlap technique are presented and discussed. These cases are: the grid of a blunt-nose cylinder, (BNC), embedded within a Cartesian farfield, with finest level and multi-level grid connections, where the flow Mach number is 1.6, and the angle of attack is 32o; the grid of BNC is overlapped within a farfield mesh of similar topology for the same flow conditions as the previous case; an ogive-nose cylinder, (ONC), in the proximity of a flat plate, where the flow Mach number is 2.86; a cylindrical store model connected to an L-shaped sting, embedded within a Cartesian farfield, where the flow Mach number is 1.65; a different cylindrical store model with fins and a curved sting in the proximity of a cavity. These cases are used for developing the procedure for overlapping grids of different topologies, and to evaluate the grid connection and interpolation data for finite volume calculations on a composite mesh. The flow solutions are obtained for all the cases, except the one which involves the cavity. Time fluxes are transferred between mesh interfaces using a trilinear interpolation procedure. Conservation losses are minimal at the interfaces using this method. The multigrid solution algorithm, using the coarser grid connections, improves the convergence time history as compared to the solution on composite mesh without multi-gridding. A 24% savings of computational time was accomplished with only two grid levels of the composite mesh, for the case of the blunt-nose cylinder grid embedded within a Cartesian mesh.

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DOI

10.25777/w1sf-wn06

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