A Novel Multiscale Methodology for Simulating Tunnel Ventilation Flows During Fires

Colella, Francesco; Rein, Guillermo; Borchiellini, Romano; Torero, José L.

doi:10.1007/s10694-010-0144-2

Cited by 46 publications

(46 citation statements)

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“…The effect was clearly evident in the small scale experiments presented by Lee et al [13,14], who first described the phenomenon, and in the full scale Runehamar tunnel fire tests [23], where the flow was throttled by about 30 % (from about 3 m s -1 to just over 2 m s -1 ) as the fire grew to its maximum size. The effect was also identified numerically by Colella [19,20], using a different model, with very different geometry and input parameters to the simulations described here.…”

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confidence: 81%

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Investigating the Throttling Effect in Tunnel Fires

2015

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Abstract. Critical ventilation velocity remains the most studied phenomenon in the tunnel fire literature. But focus on the velocity as the principal parameter may hide other features of the interaction between a fire and tunnel flow. The throttling effect was identified in the 1960s and described in the 1970s, yet it seems to be generally overlooked these days. In essence, the throttling effect is the tendency of a fire in a tunnel to resist the airflow; the larger the fire, the greater the resistance. Thus, while it has been shown that no increase in longitudinal flow velocity is required to control smoke from fires larger than the 'super critical' limit, in practice, an increasing number of ventilation devices are required to achieve this flow, and hence control the smoke from a fire, as the fire size grows. A CFD modelling study using the FDS model has been carried out to demonstrate this effect. It is clearly demonstrated that for fires larger than the 'super critical' limit, an increasing number of jet fans are required to control the smoke from increasingly larger fires. The results of the modelling study are presented.

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confidence: 81%

“…Recent modelling studies by Colella et al [19,20] employed a multi-scale modelling approach to tunnel ventilation and explicitly modelled the ventilation devices as well as blockages and fires in the tunnel, without imposing flow as a boundary condition. In this way the throttling effect was essentially 'rediscovered'.…”

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confidence: 99%

Investigating the Throttling Effect in Tunnel Fires

2015

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“…This phenomenon was recently rediscovered by Colella et al in modelling studies of tunnel ventilation in which the ventilation fans were explicitly modelled as well as the fire [71,72]. In subsequent research by Vaitkevicius et al (2014) [21,22], throttling was examined using CFD modelling using FDS to demonstrate the effects of throttling on the critical ventilation velocity.…”

Section: Throttlingmentioning

confidence: 99%

Fires in Ducts: A review of the early research which underpins modern tunnel fire safety engineering

Byrne

Georgieva

Carvel

2018

Tunnelling and Underground Space Technology

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Temperature difference due to stratification (K) ∆ Local gas temperature rise (K) ∆ %&'Average gas temperature rise (K) AbstractMuch of the early research which now underpins tunnel fire safety design was carried out experimentally, using small scale ducts. This paper reviews such experiments, mostly carried out in the 1960s, 1970s, and 1980s, highlighting the assumptions and limitations of the early studies, which may have been forgotten as the equations developed have been applied in practice in the subsequent years. The review covers three primary topics; fire propagation under 'turbulent slug flow' conditions, stratification & flame spread, and backlayering & critical ventilation velocity.

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“…The computational cost escalates with the tunnel length and often becomes impractical for engineering purposes even for medium tunnels less than 500 m long. The task is near impossible for large tunnels (kilometers long).Studies of ventilation and fire-induced flows in tunnels [1][2][3] pointed out that in the vicinity of operating jet fans or close to the fire source the flow field has a complex 3-D behavior with large transversal and longitudinal temperature and velocity gradients. The flow in these regions needs to be calculated using…”

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confidence: 99%

“…Studies of ventilation and fire-induced flows in tunnels [1][2][3] pointed out that in the vicinity of operating jet fans or close to the fire source the flow field has a complex 3-D behavior with large transversal and longitudinal temperature and velocity gradients. The flow in these regions needs to be calculated using CFD tools since any other simpler approach would only lead to inaccurate results.…”

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confidence: 99%

Time-dependent Multiscale Simulations of Fire Emergencies in Longitudinally Ventilated Tunnels

Colella¹,

Rein²,

Verda³

et al. 2011

Fire Safety Science - Proceedings of the 10th International Sym

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This paper applies a novel and fast multiscale approach to model ventilation flows and fires in tunnels. The complexity and high cost of full CFD models and the inaccuracies of simplistic zone or analytical models are avoided by efficiently combining mono-dimensional (1-D) and CFD (3-D) modeling techniques. The multiscale model couples a 3-D CFD solver with a simple 1-D model allowing for a more rational use of the computational resources. The 1-D network models tunnel regions where the flow is fully developed (far field), and detailed CFD is used where flow conditions require 3-D resolution (near field). The multiscale method has been applied to model steady-state fires and tunnel ventilation systems, including jet fans, vertical shafts and portals, and it is applied here to study the transient flow interactions in a modern tunnel of 7 m diameter section and 1.2 km in length. Different ventilation scenarios are investigated to provide the timing to reach the critical velocity conditions at the seat of the fire and to remove the upstream back layering. The much lower computational cost is of great value, especially for parametric and sensitivity studies required in the design or assessment of real ventilation and fire safety systems. This is the first time that a comprehensive analysis of the transient fire and ventilation flow scenarios in a long tunnel is conducted.KEYWORDS: tunnel fires, multiscale modeling, CFD, smoke management, detection. THE NEED FOR MULTISCALE MODELLINGFire disasters like Mont Blanc tunnel (Italy, 1999) and the more recent three fires in the Channel Tunnel (2008, 2006 and 1996) show that tunnel fire emergencies must be managed by a global safety system and strategies capable of integrating detection, ventilation, evacuation and firefighting response, keeping as low as possible damage to occupants, rescue teams and structures. Within this safety strategy, the ventilation system plays a crucial role because it takes charge of maintaining tenable conditions to allow safe evacuation and rescue procedures as well as fire fighting. The transient interaction between tunnel ventilation flows and fire dynamics is an important issue in tunnel fire protection.The study of tunnel ventilation flows and fires is most economical and time efficient when done using computer models. The most computationally cheap models are 1-D models which were developed in the 1970s. These provide the overall behavior of the ventilation system under the assumptions that all the fluiddynamic quantities are effectively uniform in each tunnel cross section and gradients are only present in the longitudinal direction. Because 1-D models have low computational requirements, they are especially attractive, and are widely used by industry, for parametric studies where a large number of simulations is required.Computational fluid dynamics (CFD) remains the most powerful method to predict the flow behavior due to ventilation devices, large obstructions or fire. In the last two decades, the application of CFD as a predi...

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A Novel Multiscale Methodology for Simulating Tunnel Ventilation Flows During Fires

Cited by 46 publications

References 20 publications

Investigating the Throttling Effect in Tunnel Fires

Investigating the Throttling Effect in Tunnel Fires

Fires in Ducts: A review of the early research which underpins modern tunnel fire safety engineering

Time-dependent Multiscale Simulations of Fire Emergencies in Longitudinally Ventilated Tunnels

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