E-Thesis 142 views 94 downloads
Parallel computational strategies for modelling transient Stokes fluid flow. / Wei Liu
Swansea University Author: Wei Liu
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Abstract
The present work is centred on two main research areas; the development of finite element techniques for the modelling of transient Stokes flow and implementation of an effective parallel system on distributed memory platforms for solving realistic large-scale Lagrangian flow problems. The first par...
| Published: |
2006
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa42737 |
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| Abstract: |
The present work is centred on two main research areas; the development of finite element techniques for the modelling of transient Stokes flow and implementation of an effective parallel system on distributed memory platforms for solving realistic large-scale Lagrangian flow problems. The first part of the dissertation presents the space-time Galerkin / least-square finite element implicit formulation for solving incompressible or slightly compressible transient Stokes flow with moving boundaries. The formulation involves a time discontinuous Galerkin method and includes least-square terms in the variational formulation. Since the additional terms involve the residual of the Euler- Lagrangian equations evaluated over element interiors, it prevents numerical oscillation on the pressure field when equal lower order interpolation functions for velocity and pressure fields are used, without violating the Babuska-Brezzi stability condition. The space-time Galerkin / least-square formulation has been successfully extended into the finite element explicit analysis, in which the penalty based discrete element contact algorithm is adopted to simulate fiuid-structure or fluid-fluid particle contact. The second part of the dissertation focuses on the development of an effective parallel processing technique, using the natural algorithm concurrency of finite element formulations. A hybrid iterative direct parallel solver is implemented into the ELFEN/implicit commercial code. The solver is based on a non-overlapping domain decomposition and sub-structure approach. The modified Cholesky factorisation is used to eliminate the unknown variables of the internal nodes at each subdomain and the resulting interfacial equations are solved by a Krylov subspace iterative method. The parallelization of explicit fluid dynamics is based on overlapping domain decomposition and a Schwarz alternating procedure. Due to the dual nature of the overlapping domain decomposition a buffer zone between any two adjacent subdomains is introduced for handling the inter-processor communication. Both solvers are tested on a PC based interconnected network system and its performances are judged by the parallel speed-up and efficiency. |
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| Keywords: |
Computer engineering.;Fluid mechanics. |
| College: |
Faculty of Science and Engineering |