Improved Fire Modelling

Mahmoud Assad

    Research output: ThesisDoctoral Thesis

    Abstract

    This thesis describes the development and validation of a modified eddy viscosity model to take into account the misalignment between stress aij and strain Sij fields for reacting flow. The stress-strain misalignment is quantified by introducing a Cas=-aijSij/√2SijSij parameter. A new transport equation for Cas was derived from a full Reynolds stress model (RSM). The Cas transport equation was coupled to a standard EVM model (e.g. k-ω SST) to form three equations model. This model is a new version of the SST-Cas 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-Cas 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-Cas 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.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Awarding Institution
    Supervisors/Advisors
    • Prosser, Robert, Supervisor
    • Revell, Alistair, Supervisor
    Thesis sponsors
    Publication statusPublished - 2014

    Keywords

    • Fire engineering
    • Combustion
    • Turbulence
    • Buoyancy
    • RANS Modelling

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