A Conservative Interblock Communication Algorithm for Dynamically Discontinuous Block Boundary Grids

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Title: A Conservative Interblock Communication Algorithm for Dynamically Discontinuous Block Boundary Grids
Author: Bond, Ryan Bomar
Advisors: Dr. D. S. McRae, Chair
Dr. J. R. Edwards, Member
Dr. H. A. Hassan, Member
Dr. R. E. White, Member
Abstract: An algorithm is presented for the conservative communication between gridblocks where point connectivity is not maintained across across theinterface. The algorithm is specifically designed for dynamicdiscontinuities, e.g. those that arise when dynamic r-refinementadaptation is performed on two adjacent blocks without the constraint ofboundary point connectivity. r-Refinement adaptation involves moving thepoints in the computational mesh to better resolve features in thesolution field. Discontinuously connected multiblock boundaries arenecessary for problems where adjacent blocks have significantly differentadaptation requirements or problems where one block is to be adapted whilean adjacent block is left stationary. In programs where adaptation isbeing performed in parallel, discontinuously connected multiblockboundaries allow the adaptation to continue on different processorswithout the need for communication and subsequent agreement of where theboundary points should be located. The communication between two adjacent blocks must be conservative toallow the simulation of compressible flow problems. Simply interpolatingthe boundary data to transfer information from one block to the otherviolates conservation, so other means of transferring the information mustbe employed. A technique for generating ghost cells and setting theirdependent variable values is presented. The method is conservative,accurate, robust, and computationally efficient. Tests of the algorithm on both statically and dynamically discontinuousgrids are presented, and the computational efficiency of the algorithm isdiscussed. The algorithm was tested using the diffusion equation, linearwave equation, and the set of Euler equations. Since the algorithm isapplicable to any CFD problem where conservative communication isnecessary between discontinuous blocks, it can be used when adaptationcriteria are different between adjacent blocks, when an adapted block isadjacent to an unadapted block, or when enhanced parallelism can beachieved by relaxing boundary point connectivity.
Date: 2001-07-11
Degree: MS
Discipline: Aerospace Engineering
URI: http://www.lib.ncsu.edu/resolver/1840.16/804

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