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Temperature and smoke spread in the early stage of a fire were modeled, using computational fluid dynamic techniques, and compared with data obtained from field tests conducted in an operating roadway tunnel in the City of Montreal, Canada. Fire characteristics, including temperatures and smoke spread over the tunnel were measured during these tests. Two types of fire scenarios were simulated: gasoline pool fires under vehicles and gasoline pool fires behind vehicles. The estimated fire size used in the simulations was 650 kW. The initial and boundary conditions of each simulation were set to mimic the conditions of the corresponding test. Comparisons were made to temperature and smoke optical density measurements. In general, favourable comparisons between the numerical predictions and the experimental data were observed. The ceiling temperature downstream of the fire decreased with an increase in the distance from the fire source, which is also the case for smoke optical density. The ceiling temperatures produced by the fire behind the vehicle were higher than those produced by the fire under the vehicle. The temperature variation along the central cross section of the tunnel shows that the highest ceiling temperature occurs 3~5 m downstream of the fire because the plume was tilted by the airflow inside the tunnel. Fire location had a significant impact on ceiling temperature development in the tunnel. The airflow conditions at the fire location significantly affect smoke and temperature distributions in the tunnel which will also affect the performance of detection systems. [ABSTRACT FROM AUTHOR]

A research project has been conducted at the National Research Council of Canada (NRC) to evaluate the effectiveness of in-place emergency ventilation strategies to control smoke spread in the event of a fire in a road tunnel. Some of these strategies date back to the design of the tunnel (1964). Following a recent fire, the operating instructions were revised. A scientific based evaluation of these operation instructions is the main objective of the research study. The research includes both numerical and experimental studies. The numerical study uses the Computational Fluid Dynamics (CFD) model Fire Dynamic Simulator (FDS) to investigate smoke ventilation in tunnels. The experimental study is used to provide the necessary initial and boundary conditions for the CFD model. In-situ fire tests were conducted in an operating road tunnel using a fire source of 2 MW (1.9 x 103 BTU/s). Temperature, airflow velocity, pressure and smoke optical density (SOD) values were measured. These data was used to validate the numerical model against small fires. CFD simulations were conducted to compare with measured field data. Comparisons were made, at the near and the far field of the fire source, of several parameters included: volumetric airflow, temperature, and SOD values The CFD simulations were able to replicate field tests trends. They provided insight into phenomena observed during the in-situ fire tests. This understanding had been used as the basis to improve the performance of tunnel ventilation system to control smoke spread. The comparison studies showed that both numerical predictions and experimental measurements were, in general, comparable. As such, the validated CFD model can be used to complement the experiments to analyze different fire and ventilation scenarios. They offer a predictive tool for the situations where the actual fire tests prove to be cumbersome to conduct. [ABSTRACT FROM AUTHOR]

A research project is being conducted at the National Research Council of Canada (NRC) to evaluate the effectiveness of current emergency ventilation strategies to control smoke spread in the event of a fire in two road tunnels. The research study includes numerical and experimental phases. The numerical phase uses computational fluid dynamics (CFD) models to study smoke ventilation in the tunnels. The experimental phase is used to calibrate and to partially validate the chosen CFD models and to provide the necessary initial and boundary conditions. SOLVENT, a CFD model, was used to model ventilation scenarios using existing data. The current paper presents the efforts to validate the CFD model against on-site flow and fire test measurements conducted in a 1.8 km road tunnel. The CFD model includes aerodynamically significant physical features of the tunnel and is customized to provide general roughness replicating the actual roughness in the tunnel. [ABSTRACT FROM AUTHOR]