Another application field is the reconstruction of real fires, as in, where the Hsuehshan tunnel fire has been simulated using FDS. Regarding tunnel fires, most applications aim at providing practical evaluations of phenomena such as smoke movement in tilted tunnels, as in, and backlayering, as in. Still, in several applications, the main approach to simulate fires in the actuality is CFD, as it tends to be more precise and describe the physics in a more accurate way.ĬFD has been largely used to simulate fires from confined fires, to extinction modelling and tunnel fires. Then, zone models have been developed, BRANZFIRE, FSSIM, CFAST, focusing in simulating fires in compartments that might be linked in a network, like rooms in a building. The attempts started with 1D models like MFIRE, SPRINT, WHITESMOKE, which have been applied to underground network structures, such as tunnels or mines. Simulation of fire scenarios of different characteristics has represented an intensely researched topic in the last years. Because of this, CFD calculations are still unable to give fast-enough results for these applications and need some developments that help shortening simulation times. Despite the continuously growing calculation speed of computers, CFD remains time costly, especially for long tunnels.
With the advancement of technology also new applications are developed like ventilation and emergency systems management in tunnels, risk assessment and VR training.
Furthermore, the multiscale manages to reduce the computational time of more than a 50%.Ĭomputational Fluid Dynamics (CFD) software packages have been constantly used to simulate tunnels and substitute on-site tests. The difference in temperature and velocity is minimal for most of the domain, making It a good way to optimize resource usage in large simulations.
As a final step, the model is tested in a tunnel with a cross section of 4.8 m and 600 m of length with a 2 MW fire, comparing its performance with a full 3D FDS simulation. Our research verifies most of its capabilities, also clarifying its limitations and the criteria used to set the domain for the analysis. Some new characteristics are pressure boundary conditions can be easily imposed at the tunnel portals or at the ventilation shafts the characteristic curves of the fans/jet-fans can be included, also considering the degradation effects due to smoke propagation the piston effect can be properly considered. Also, additional simulation capabilities particularly useful for tunnel analysis are obtained.
Using this multiscale model, the computation time for long tunnels is reduced, proportionally to the 1D length in the domain. Whitesmoke manages the fluid dynamics, temperature and concentration of species in the 1D portion, while FDS calculates these fields in the portion where fire occurs.
The model incorporates the code Whitesmoke into FDS (Fire Dynamics Simulator) through a direct coupling. To face this need, a novel 1D–3D multiscale model is presented in this paper. This introduces a need for methods able to reduce the amount of time required for simulations. Even when the computational capacity of computers has grown, CFD is still constrained by the large amount of computational resources needed in long tunnels.
As technology advances, new application opportunities appear some examples are the optimal operation of ventilation and emergency systems, risk assessment of tunnels and training of the operators. Computational Fluid Dynamics (CFD) is widely used to simulate tunnels and partially substitute on-site tests.