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Large Eddy Simulations (LES) of smoke extraction duct system (SEDS) in single compartments of different volumes (i.e., 128 m 3 , 512 m 3 and 2400 m 3 ) with FDS 6.5.3 are presented. The required grid resolution for accurate flow inside the duct systems is discussed and the influence of different SEDS design parameters (i.e., shape and position of duct system, number and position of extraction openings) on the smoke extraction efficiency of the system is analysed. The extraction rates applied to the SEDS are determined a-priori based on simplified calculations with these estimates compared against the predicted CFD results (i.e., in terms of predicted smoke free heights inside the compartments). Overall, the numerical predictions are satisfactory (i.e., within less than 5 % errors) in most of the scenarios considered, apart from the 2400 m 3 compartments, where the smoke free heights are 20 % lower than expected. The analysis of the numerical simulation results reveals some important aspects, including that the use of multiple extraction openings is not efficient, in terms of smoke extraction, in the same duct of the same compartment and that the local velocities, at the level of the extraction openings, can potentially exceed the maximum allowed design values. Among the SEDS design parameters, the position and shape of the duct (i.e., rectangular or flat) as well as the position of the extraction opening(s) do not have a significant influence in terms of predicted smoke free heights. [ABSTRACT FROM AUTHOR]

Investigations of ventilation in an immersed tunnel have recently drawn greater research attentions; however, analyses on the influence of vent design and tunnel width on ventilation performance have rarely been addressed. For the sake of the security of evacuees in an immersed tunnel fire, the influence of three vent designs and two immersed tunnel widths on mechanical ventilation performance during tunnel fires were numerically investigated using large eddy simulation. The pollutant gas flow characteristics in the tunnel after a fire were analyzed, and the pollutant gas exhaust efficiency based on the mass conservation of carbon monoxide in the smoke was proposed in this study. By comparing the smoke propagation, smoke distribution, and exhaust efficiency between three different vent designs, it was determined that the Top Vent Design has the best smoke exhaust effect, and the Sidewall Vent Design (with an activated vertical smoke screen) has a better smoke exhaust effect than the Sidewall Vent Design. The influences of the tunnel width and heat release rate of the fire on the ventilation effect were also investigated. [ABSTRACT FROM AUTHOR]

Long evacuation time is a key fire safety concern for crowded supertall buildings. Elevator evacuation appears to be the only choice but fire safety provisions are not specially designed for the use of elevators. A fire safe elevator system was proposed earlier for supertall buildings by providing elevator accessible on each floor level and passing through the refuge place. The fire hazard associated with this design has been studied numerically through an example building in this paper. Smoke spread to the elevator system was considered in the study. The effect of ventilation of the shaft, stack effect and wind effect on smoke movement were studied by empirical equations in fire engineering and justified by computational fluid dynamics. Different designs of smoke extraction with pressurization system were evaluated by analysing the smoke dispersion and pressure distributions. The effect of fire at different heights on smoke spread was also investigated. Results show that the smoke extraction system can only delay smoke spread to the elevator shaft near the fire source for a short time. The "four-floor approach" pressurization system can confine the smoke in the area of fire floor for a sufficiently long time period for safe evacuation. [ABSTRACT FROM AUTHOR]

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Copyright of Bautechnik is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)