Large Eddy Simulation of Propylene Turbulent Vertical Wall Fires

Ren, Nanqi; Wang, Y.; Vilfayeau, S.; Trouvé, Arnaud

doi:10.3850/978-981-07-5936-0_04-04

Cited by 5 publications

(8 citation statements)

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“…There is simply too much uncertainty to allow pinpointing where exactly modeling or accuracy needs to be improved to date. This is in line with the statement that '… wallresolved simulations are considered a necessary first step on the route to develop wall models', in the context of turbulent vertical wall fires [6]. Nevertheless, one could think of an experiment as well, using a gas burner (with, e.g., a long narrow slit nozzle) from which gaseous fuel emerges at low velocity (so the set-up is buoyancy driven).…”

Section: Examples Of Possible Bench-marking Studiessupporting

confidence: 66%

“…Boundary layer flows occur with convective (and radiative) heat transfer. Such simulations are strongly mesh dependent, as reported in, e.g., [6], where wall-resolved LES simulations are discussed. Wall-resolved LES simulations require very fine computational meshes, but, for the sake of research purposes, are worthwhile doing for a range of test cases, generating 'reference results'.…”

Section: Examples Of Possible Bench-marking Studiesmentioning

confidence: 92%

“…The D * /10 criterion is also not expected to be sufficient when fire dynamics is concerned, with interaction between gas phase and condensed phase phenomena. Flame spread simulations, involving boundary layer flows with convective (and radiative) heat transfer, are strongly mesh dependent [6]. Also simulations of liquid pool fires are currently highly mesh sensitive, particularly when the evaporation model uses the state in the first cell, adjacent to the pool surface, for the mass transfer (burning rate).…”

Section: Requirements For the Computational Meshmentioning

confidence: 99%

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Computer Modeling for Fire and Smoke Dynamics in Enclosures: A Help or a Burden?

Merci¹

2014

Fire Saf. Sci.

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Fire simulations are of unique value in different respects: for fire safety system design calculations, for improving our understanding (theory and model development and validation) and for fire forecasting. In this paper the effective use of computing power for the further development of fire safety science is discussed, considering only gas phase phenomena in fire and smoke dynamics in enclosures. Arguably, much effort needs to be devoted to multi-phase phenomena (pyrolysis modeling, the effect of water or other suppressants, etc.), but this is not discussed in the paper at hand.A common feature to all types of simulations is that the Required Computing Resources (RCR), determined by the envisaged accuracy and the complexity of the problem to be tackled, must be less than the Available Computing Resources (ACR). Accuracy, reliability and dimensionality of the models used, must therefore be related to the problem tackled. In order to make progress, bench-marking studies, as a joint effort made by modelers and experimentalists, with transparent communication, are argued to be a good approach for systematic progress in the development of, and confidence in, models.Using Computational Fluid Dynamics (CFD) can be very valuable for the development of theory and the study of detailed fluid mechanics phenomena, but several aspects are important to guarantee the quality of the results. Some ideas will be formulated on how to investigate requirements on the computational mesh. Turbulence -chemistry interaction (TCI) and turbulence -radiation interaction (TRI) are also discussed briefly. Yet, it is argued that a major source of uncertainty in computer simulations stems from (and will continue to stem from) the characterization of the ever changing and developing materials (i.e. the fuel), as well as from geometry dependent features (including ventilation and heat transfer). This affects the combustion and soot formation, and therefore the fire and smoke dynamics. Therefore, a user-defined fire will remain indispensible in the foreseeable future when using computer modeling for the sake of design of fire safety systems. Once this fire has been defined, CFD is best suited in regions where detail is required or complex flow patterns establish, while other forms of modeling can be considered in other regions.For real-time and forecasting applications, it is argued that sensor-assisted numerical simulations are very promising and their use is expected to become widespread in the coming decades. With increasing computing power, the use of CFD will become more feasible in this context, but for the time being zone model calculations (perhaps combined with CFD in regions where more detail is required) seem better suited to that purpose.

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Section: Examples Of Possible Bench-marking Studiessupporting

confidence: 66%

Section: Examples Of Possible Bench-marking Studiesmentioning

confidence: 92%

Section: Requirements For the Computational Meshmentioning

confidence: 99%

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Computer Modeling for Fire and Smoke Dynamics in Enclosures: A Help or a Burden?

Merci¹

2014

Fire Saf. Sci.

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“…As shown in Ref. [22], the wall-normal grid resolution for a wall-resolved fire case should be on the order of 2 mm. For a coarser grid, a turbulent thermal diffusivity is calculated based on the ratio of mean heat flux predicted from the wall-resolved simulation to the resolved convective heat flux by the coarser mesh.…”

Section: Model Descriptionmentioning

confidence: 99%

“…An empirical wall function derived from a wall-resolved LES study of vertical wall fires [22] is used in the current simulation for convective heat transfer. As shown in Ref.…”

Section: Model Descriptionmentioning

confidence: 99%

Numerical Simulation of Sprinkler Suppression of Rack Storage Fires

Wang¹,

Meredith²,

Zhou³

et al. 2014

Fire Saf. Sci.

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Fire suppression tests with ceiling sprinkler protection in a rack storage fuel configuration are simulated using a Computational Fluid Dynamics tool. The fuel is arranged in a double-row, six pallet-load wide and three-tier high (2×6×3) rack storage array. Each pallet load consists of three nested double-wall corrugated cardboard boxes surrounding a metal liner. Two types of ceiling sprinklers are used in this study: a pendent quick response sprinkler designated as K14, and an upright standard response sprinkler designated as K11.2. The tests are simulated using FireFOAM, which couples necessary sub-models for fire growth, sprinkler response, and fire suppression. Numerical results are compared with experiments for both free burn tests under a 20-MW calorimeter and sprinkler suppression tests under a 7.6 m high ceiling. For the free burn case, the model results show good quantitative agreement of heat release rates in all three phases, from ignition to fire growth and steady burning. For the suppression cases, the model reproduces the suppression effectiveness of the two sprinkler protection designs: K14 sprinklers suppress the fire rapidly with only one sprinkler activation, while with K11.2 sprinklers, both in the tests and simulation, the fire spreads to the pallets on the end of the fuel array with multiple sprinkler activations. The modeled sprinkler activation times are within the estimated experimental uncertainty following three repeat tests. Quantitative results characterizing sprinkler suppression performance obtained from the simulations, such as the actual delivered density (ADD) and water evaporation rate, are also reported.

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