Calibrating a goods vehicle fire growth in a tunnel using FDS 5.5

• Main Author: Kusuma, Darwin.
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Mechanical engineering::Fluid mechanics
• Online Access: http://hdl.handle.net/10356/46031
• Institution: Nanyang Technological University

A fire in road tunnel can occur from car accidents or explosion and possibly turn into huge and dangerous disaster if not addressed properly. The smoke arisen from the fire can fill up both upstream and downstream of the fire. Tunnel ventilation system is highly important to push the smoke away from the fire site to create a safe evacuation path for motorists‟ evacuation as well as to facilitate fire fighters to access the fire location for fire and rescue operation. In designing a tunnel ventilation system, several parameters need to be considered such as heat release rate, tunnel geometry, tunnel gradient, and the ventilation condition in the tunnel. In the last five decades, fire researchers and scientists have been conducting fire tests in road tunnels to investigate the effect of these parameters. Several well-known projects such as EUREKA EU-499 and Mont Blanc Tunnel fire tests are briefly described in this thesis. However, real fire tests in road tunnels are generally expensive and complicated to perform resulting in minimum available experimental data for more thorough analysis. Therefore, an approach of using computational fluid dynamics (CFD) modelling is discussed to study the fire cases and tests by using simulation software. An example of CFD modelling for the Memorial Tunnel fire tests is also presented. One approach in the CFD modelling is to use prescribed heat release rate which values can be obtained from international standards or guidelines. For instance, in the Permanent International Association of Road Congresses (PIARC) document and National Fire Protection Association (NFPA) standard, a heavy goods vehicle is estimated to produce fire size of 20-30 MW. However, recent large-scale fire tests carried out in Runehamar Tunnel showed higher heat release rate which may imply that the standardized heat release rate value might have been underestimated. This research dissertation presents a modelling approach which aims to predict rather than prescribe the heat release rate. The modelling approach makes use of Fire Dynamics Simulator (FDS 5.5), a CFD software which is suitable for low-speed, thermally-driven flow. The underlying equations and assumptions will be discussed. In this modelling and simulation works, factors such as the fuel load, tunnel geometry, and ventilation condition will be considered. The modelling process and the assumptions made are elaborated. Finally, this report also discusses the effects of different fuel load configurations, diverse tunnel lengths, and various ventilation speeds on the heat release rate. Grid independent test was performed to examine the appropriate resolution for the simulation.