A series of CFD fire predictions of a 100 MW Memorial tunnel fire test are performed toinvestigate several factors that influence the outcome of CFD fire simulations of large scale tunnel firescenarios. This study shows that at the critical ventilation velocity, the occurrence of back-layering isvery sensitive to factors such as variation in ventilation velocity, tunnel surface condition, the width ofthe modelled fire source and the presence of relatively minor obstacles in the vicinity of the firesource. A serious question has also been raised over the suitability of the use of inlet boundaryconditions to represent the ventilation flow generated by jet fans. To a large extent, the success ofsimulating a tunnel fire test such as the Memorial Tunnel test relies on correct replication of the testconditions and setup. However, for most large scale tunnel tests, not all the information required tocorrectly specify a CFD fire simulation is available and hence sensitivity analyses over critical modelsetup parameters is essential to correctly interpret differences between predictions and experimentalmeasurements.
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