1,720,966 research outputs found
Numerical simulation of full-scale enclosure fires in a multilevel library
No full textIn accordance with European policy, Italian regulations concerning building fire safety have been reformulated from prescriptive into performance-based rules. In this context field modeling based on Computational Fluid Dynamics methodology can potentially be applied to fire safety design in order to assess the performance of different designs and safety measures over a wide range of scenarios, so as to minimize the potential danger to life and property. In this work, a CFD code has been used to estimate the consequences of a fire occurring in a multilevel library. The evolution of gas temperatures, velocity field, radiative heat flux, gas and smoke concentrations has been predicted after the fire start. Simulation results have been evaluated with reference to tenability conditions along the evacuation paths in the building. Results have been also used to estimate the exposure to heat of the library ceilings and walls
CFD simulations for the comparison of the effectiveness of some fire protection systems in road tunnels
No full textThermal radiation modelling in tunnel fires
No full textModelling based on Computational Fluid Dynamics (CFD) is by now effectively used in fire research and hazard analysis. Depending on the scenario, radiative heat transfer can play a very important role in enclosure combustion events such as tunnel fires. In this work, the importance of radiation and the effect of the use of different approaches to account for it were assessed. Firstly, small-scale tunnel fire simulations were performed and the results compared with experimental data, then realistic full-scale scenarios were simulated. The results show up the capability of CFD modelling to reproduce with good approximation tunnel fires. Radiation proved to be noteworthy mainly when the scale of the fire is relatively large. Among the various approaches employed to simulate radiation, the use of the Discrete Transfer model gave the most accurate results, mainly when the absorption-emission characteristics of the combustion products were taken into account. Finally, the suitability of the use of CFD in quantitative Fire Hazard Analysis is discussed. © 2011 Global Science Press
Simulation of fire scenarios due to different vehicle types with and without traffic in a bi-directional road tunnel
No full textThis paper presents findings obtained by CFD modelling for simulating the effects of fire due to different vehicle types in a bi-directional road tunnel. Four different burning vehicles placed in the centre of the driving lane at tunnel middle length were considered. Peaks of the heat release rate (HRR) of: 8,30,50,and 100 MW were simulated for the two cars, the bus, the heavy goods vehicle (HGV), and the petrol tanker, respectively. The fire effects on tunnel structure and on environmental conditions along people evacuation path were especially evaluated. The effects of the traffic jam,in contrast with the isolated vehicles, on temperatures, radiant heat flux, visibility distance, and toxic gases concentrations, were also investigated. The worst scenario was identified to be that pertaining to the petrol tanker and more critical conditions were also found when the tunnel was full of vehicles. The maximum gas temperatures reached in the presence of traffic at the side wall (and at the tunnel ceiling reported in brackets) were found to be:360C (170 C) for the two cars;740 C (465 C) for the bus; 835 C (735 C) for the HGV and 1305 C (1145 C) for the petrol tanker, respectively. The presence of the traffic, in contrast with the isolated vehicle, involved an increase in the maximum temperatures equal to 16–17% for the two cars,and contained in the range 12–29% with percentages increasing starting from the tanker, to the HGV and to the bus. In other words when the maximum temperatures produced by the isolated vehicle are very high (e.g. for the tanker), the presence of the traffic had a minor effect. With reference to environmental conditions along the evacuation path, the results showed that in the case of petrol tanker fire the emergency ventilation ensures a tenable level of temperature, radiant heat flux, and toxic gases concentrations up to 5 min from the fire starting.This time increases up to 6.5 min for the HGV and 8 min for the bus.This means that the tunnel users in order to be safe in all scenarios should leave the tunnel within 5 min after the fire starting.Toxic gases concentrations, however, were found to be below the limit values in all cases and also in the presence of traffic. In the light of the aforementioned results, tunnel occupants should be promptly informed of the fire risk and guided to the exit portals.This might be done by equipping the tunnel with illuminated emergency signs located along the tunnel length and by installing traffic lights before the entrances so that the tunnel can be closed in case of emergency. By activating the traffic lights at the portals and the emergency signs (more especially those at the ceiling) at the same time as the emergency ventilation is activated, safer conditions for the people evacuation are expected
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