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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/860

Title: Automated parallel mesh adaptation methods for transient flowfield analyses with fixed or moving boundaries
Authors: Cavallo, Peter Angelo
Keywords: Mechanical engineering;Fluid dynamics;Parallel computers
Issue Date: 27-Jul-2006
Abstract: Transient flowfields appear in many applications of interest and present numerous challenges to current simulation methods. Such problems include shock propagation and reflection, bluff body wakes with periodic shedding, and pulsatile flows generated by flow control devices. Also of interest are cases where boundaries are in relative motion, as found in weapons separation from aircraft, valve and piston motion in internal combustion engines, and rotor/stator interactions. The task of providing a computational mesh that is adequate to capture evolving flow structures as they change in time is an important and difficult aspect of this class of simulations. In moving body applications, the problem is compounded by the need to accommodate topology changes in the mesh. The issue of spatial resolution in transient flows has been addressed by various researchers using adaptive mesh refinement. However to date such strategies have largely been ad hoc and problem-dependent. The simulation of bodies undergoing relative motion has typically been performed using overset grid methods, which require considerable expertise and can be significantly labor intensive, particularly when generating overlapping grids for realistic geometries. This work presents new approaches for performing unstructured mesh adaptation for transient flows with fixed or moving boundaries. Notable advances in parallel mesh adaptation methods are made to facilitate the integration of mesh coarsening and refinement within the iteration loop, operating directly on the decomposed domains used by the parallel flow solver. A novel method is developed which modifies the mesh automatically at variable intervals according to how rapidly the solution is changing, rather than relying on a predefined, constant frequency. The new approach is founded on the concept of projecting refinement of solution errors ahead of their current location, and subsequently monitoring their accumulation. For moving boundary problems, a formal mesh deformation matrix analysis is employed to direct where corrective coarsening and refinement are required. Automation of mesh corrections for such problems is based on the deformation history of the mesh. These advances are demonstrated on controlled, unit problems as well as more complex problems of interest involving stationary and moving geometries.
URI: http://hdl.handle.net/1860/860
Appears in Collections:Drexel Theses and Dissertations

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