Title: Buoyancy-generated turbulent flows in semi-enclosed regions: a computational fluid dynamics study

Authors: Marina K-A. Neophytou, Rex E. Britter

Addresses: Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK. ' Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK

Abstract: In recent years, fires in tunnels have occurred frequently, often with tragic outcomes. A recent example is the fire on the funicular train at the ski resort in Kaprun, Austria, which caused nearly 160 deaths. Design engineers and risk analysts need to know about the fluid dynamics of the fire and the smoke movement in order to answer questions such as: how much oxygen can access and feed the fire, and to what concentration of smoke people are exposed. In the Austrian accident, the geometry involved was that of a long, inclined tunnel with fire doors closed at one end, and with a fire initiated near the closed (lower) end. The hot smoke from the fire is a source of buoyancy; the smoke reaches the ceiling of the tunnel and then develops along the ceiling as a wall-bounded plume. The motion of the smoke is driven by a buoyancy force, but at the same time, a mechanism of turbulent mass and heat transfer acts as a brake to this motion. The present study investigates the dynamics of this class of flows and produces models for their qualitative and quantitative description. It concludes that the mean propagation velocity (U) scales with the released buoyancy flux per unit depth as F01/3 and determines the effects of tunnel inclination on the dynamics of the flow.

Keywords: ventilation; heat transfer; mixing; entrainment; smoke; fires; tunnels; modelling; confined flows; CFD; computational fluid dynamics; turbulent flows; buoyancy.

DOI: 10.1504/PCFD.2006.009491

Progress in Computational Fluid Dynamics, An International Journal, 2006 Vol.6 No.1/2/3, pp.137 - 145

Published online: 05 Apr 2006 *

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