Expanding the FDS Simulation Capabilities to Fire Tunnel Scenarios Through a Novel Multi-scale Model

Abstract

Computational Fluid Dynamics (CFD) is widely used to simulate tunnels and partially substitute on-site tests. 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. Even when the computational capacity of computers has grown, CFD is still constrained by the large amount of computational resources needed in long tunnels. This introduces a need for methods able to reduce the amount of time required for simulations. To face this need, a novel 1D–3D multiscale model is presented in this paper. The model incorporates the code Whitesmoke into FDS (Fire Dynamics Simulator) through a direct coupling. 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. Using this multiscale model, the computation time for long tunnels is reduced, proportionally to the 1D length in the domain. Also, additional simulation capabilities particularly useful for tunnel analysis are obtained. 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. Our research verifies most of its capabilities, also clarifying its limitations and the criteria used to set the domain for the analysis. 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. 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. Furthermore, the multiscale manages to reduce the computational time of more than a 50%.

The Problems of Fires in Coal Mines and a Review of Modern Approaches to Their Modelling

“…Для этой цели широко используются методы компью терного моделирования, позволяющие определить поля концентраций выделяющихся при пожаре газов, темпе ратурные поля и их эволюцию с течением времени и при различных сценариях [12,13].…”

“…Их использо вание позволяет получить подробные данные о скоро сти воздушного потока, давлении, концентрации газов, тепловом потоке в моделируемой области и позволяет визуализировать сложное поведение системы [14,15]. Однако стоит отметить, что применение CfD-методов при моделировании пожаров в масштабных вентиляци онных сетях, состоящих из сотен выработок, может быть существенно затруднено по причине огромной вычис лительной сложности таких задач [13]. Сравнение ре зультатов полномаштабных экспериментов и результа тов CfD-моделирования (с использованием fDS) пока зало, что результаты численного моделирования согла суются с экспериментальными данными, при этом сред нее значение максимальных отклонений на всех участ ках составило 24% [15].…”

Knowledge Graph Construction to Facilitate Indoor Fire Emergency Evacuation

“…The existing research mainly considers fire, building, and personnel. Some studies focused on the relations between fire and building objects, especially indoor fire risk assessment supported by fire simulation [16][17][18]. Studies mainly relied on fire simulation models like Fire Dynamics Simulator (FDS) and building models like Building Information Modeling (BIM) to construct a virtual fire sce-nario by setting parameters for specific buildings.…”

A Critical Review of Fire Tests and Safety Systems in Road Tunnels: Limitations and Open Points

“…On-site tests are often replaced by simulated tunnels using computational fluid dynamics (CFD) software. Despite the time-consuming nature of CFD simulations, they are still widely used in simulating fires in tunnels and developing ventilation and emergency systems management [47]. Small-scale model tests can be useful for studying the back-layering length of fire smoke and critical velocity with canyon crosswind by changing wind velocity, longitudinal ventilation velocity, and fire position in the tunnel.…”