This thesis describes the development and validation of a modified eddy viscosity model to take into account the misalignment between stress a_{ij} and strain S_{ij} fields for reacting flow. The stress-strain misalignment is quantified by introducing a C_{as}=-a_{ij}S_{ij} /\sqrt{2S_{ij}S_{ij}} parameter. A new transport equation for C_{as} was derived from a full Reynolds stress model (RSM). The C_{as} transport equation was coupled to a standard EVM model (e.g. k-\omega SST) to form three equations model. This model is a new version of the SST-C_{as} model introduced by Revell (Revell2006), to incorporate buoyancy and combustion effects for buoyant reacting flow (e.g. fire). The performance of the proposed model was initially investigated via non-reacting buoyant plumes with different level of unsteadiness. The buoyant plumes were also simulated using different turbulence models and the results were compared to proposed model and experimental data. The model shows significant improvements for velocity and scalar profiles in region closed to plume centreline compared to the original SST model. The SST-C_{as} model was then applied for a real fire test case (Steckler room), and the results were compared to experimental data and results of RSM models. The SST-C_{as} model generally yields better than classical EVM models and reduces the gap between the RSM and EVM prediction with 25-30\% additional computational expenses. This work is still under development and validation for reacting flows, further work is going on to include the turbulence combustion interaction and validate it with DNS data.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:626926 |
| Date | January 2014 |
| Creators | Assad, Mahmoud Abdulatif |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/improved-fire-modelling(b5bf15d8-890b-4201-a800-f1c810a88ba1).html |
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