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- Holmstedt, Göran, et al.
(författare)
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Determination of uncertainty of different CFD codes by means of comparison with experimental fire scenarios
- 2009
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Ingår i: Conference Proceedings - Fire and Materials 2009, 11th International Conference and Exhibition.
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Konferensbidrag (refereegranskat)abstract
- This article will summarise the evaluation of four CFD software codes (CFX, FDS4, SMAFS and SOFIE). Evaluation was performed by means of comparing the simulation data with experimental scenarios. The scenarios were chosen to represent scenarios frequently assessed using fire safety design based on performance. The greatest difficulty during validation of CFD-codes is to find well documented relevant experiments. It is true that many large scale experiments including smoke spread have been published but many of them are not described sufficiently and are therefore impossible to use for validation. It is very unusual that data on reproducibility and repeatability is available. After an extensive discussion between the participants in the project five scenarios were chosen. Scenarios 1A (large room with vents), and scenarios 1B1 and 1B2 (corridor with vents) were well documented experiments (repeatability) with ceiling vents and ceiling jets performed earlier at SP in Boras. Scenario 2 is a tunnel fire taken from an experimental study in Boston, US. Scenario 3 is an atrium fire taken from an experimental study in Japan. Lack of well documented fires in retail premises lead us to perform a series of tests in 1/2 scale, 4.1 and 4.2 at SP in Boras. Scenario 5 is an experimental study from Australia including smoke spread from a fire room to an adjacent corridor and a room. The conditions for the simulations included information about the scenarios given above. No information about experimental results was available until the results from the simulations had been sent in to the project manager. The intention was to imitate the working conditions for a consultant as far as possible when using a CFD-simulation to estimate fire safety. In this manner the simulations are dependent on many factors such as the CFD-code used, judgement of input data of the scenarios done by the operator, operator skill etc. The results from the evaluation of the CFD codes showed that the simulation results generally were a good description of the experimental fires studied, but that limitations and specific properties of the different codes, together with the operator factor, can strongly influence the results. The detailed results of all comparisons are given in the final report of the project. It was not possible to include these detailed evaluations in this conference paper but these results are available in the main report as well as in future scientific articles.
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| 5. |
- Yan, Zhenghua, et al.
(författare)
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Analysis of Flame Radiative Heat Transfer Using Large Eddy Simulation
- 2009
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Ingår i: HT2009: PROCEEDINGS OF THE ASME SUMMER HEAT TRANSFER CONFERENCE 2009, VOL 1. - 9780791843567 ; , s. 177-186
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Konferensbidrag (refereegranskat)abstract
- Abstract in UndeterminedA series of comprehensive large eddy simulations of non-premixed turbulent hydrocarbon flames of different sizes in a typical fire scenario have been carried out to compute the flame radiative heat transfer. In the simulation, considerations include the modelling of sub-grid turbulence, turbulent combustion, soot formation, thermal radiation and interactive heat transfer inside solid walls, etc. The instantaneous thermal radiation was calculated using the discrete transfer method with the radiation property evaluated by both an approximated fast narrow band model and an integral model. Simulation was validated against experimental data. Flame radiation heat transfer was compared for flames of different sizes. The effect of thermal radiation property evaluation model on calculation of radiation and the role of thermal radiation in total heat transfer are analyzed.
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| 7. |
- Yan, Zhenghua
(författare)
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Comprehensive CFD Simulation of Fire in a Retail Premise with Analysis of Leakage Effect
- 2009
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Ingår i: Numerical Heat Transfer. - : Informa UK Limited. ; 55:1, s. 1-17
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Comprehensive simulations of fire in a retail premise from a blind validation study are presented. The simulations were made using a self-developed parallel CFD program SMAFS [1], with the turbulent flow, turbulent combustion, thermal radiation, soot formation, and the interactive heat transfer inside solid boundary all computed. The results are extensively compared with experimental measurement showing good agreement. Detailed result analysis shows the important effect of flow leakage in such a fire scenario. It is found that the leakage can alter the ventilation condition and has important influence on the gas temperature profile at low height and the flow profile at the ventilation opening. This indicates that care should be taken with the consideration of leakage in a proper CFD simulation of fire in relevant scenarios.
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- Yan, Zhenghua, et al.
(författare)
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Large eddy simulation of natural convection along a vertical isothermal surface
- 2005
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Ingår i: Heat and Mass Transfer. - : Springer Science and Business Media LLC. - 1432-1181 .- 0947-7411. ; 41:11, s. 1004-1013
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Tidskriftsartikel (refereegranskat)abstract
- Large eddy simulations of natural convection along a vertical isothermal surface have been carried out using a parallel CFD code SMAFS (Smoke Movement And Flame Spread) developed by the first author to study the dynamics of the natural convection flow and the associated convective heat transfer, with sub-grid scale turbulence modeled using the Smagorinsky model. In the computation, the filtered governing equations are discretized using finite volume method, with the variables at the cell faces in the finite volume discrete equations approximated by a second order bounded QUICK scheme and the diffusion term computed based on central difference scheme. The computation was time marched explicitly, with momentum equations solved based on a second order fractional-step Adams-Bashford scheme and enthalpy computed using a second order Runge-Kutta scheme. The Poisson equation for pressure from the continuity equation was solved using a multi-grid solver. The results including the temperature and velocity profiles of the boundary layer and the local heat transfer rate are analyzed. Comparison is made with experimental data and good agreement is found.
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| 9. |
- Yan, Zhenghua
(författare)
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Large eddy simulations of a turbulent thermal plume
- 2007
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Ingår i: Heat and Mass Transfer. - : Springer Science and Business Media LLC. - 1432-1181 .- 0947-7411. ; 43:6, s. 503-514
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Tidskriftsartikel (refereegranskat)abstract
- Large eddy simulations of a three-dimensional turbulent thermal plume in an open environment have been carried out using a self-developed parallel computational fluid dynamics code SMAFS (smoke movement and flame spread) to study the thermal plume's dynamics including its puffing, self-preserving and air entrainment. In the simulation, the sub-grid stress was modeled using both the standard Smagorinsky and the buoyancy modified Smagorinsky models, which were compared. The sub-grid scale (SGS) scalar flux in the filtered enthalpy transport equation was modeled based on a simple gradient transport hypothesis with constant SGS Prandtl number. The effect of the Smagorinsky model constant and the SGS Prandtl number were examined. The computation results were compared with experimental measurements, thermal plume theory and empirical correlations, showing good agreement. It is found that both the buoyancy modification and the SGS turbulent Prandtl number have little influence on simulation. However, the SGS model constant C (s) has a significant effect on the prediction of plume spreading, although it does not affect much the prediction of puffing.
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- Yan, Zhenghua, et al.
(författare)
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Validation of CFD Model for Simulation of Spontaneous Ignition in Bio-mass Fuel Storage
- 2005
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- Both numerical simulations and experimental measurements of small scale spontaneous ignition with different biomass fuels have been performed. In the experiments, temperature history was monitored at five different locations inside the fuel bed. The measured temperature history was used for validation of comprehensive threedimensional computer simulations which were carried out using a parallel finite volume CFD code SMAFS (Smoke Movement and Flame Spread) developed by the first author. The computation was based on numerical solution of a set of governing equations including the continuity equation, extended Darcy momentum equations, energy conservation equations for both gas and solid phases, and mass conservation equations for different chemical species. With reliable material properties input data provided by separate measurements, it simulated the temporal state evolution inside the biomass fuel storage. In the simulation, consideration was given to a series of essential physical and chemical processes, including convection and diffusion in porous media, evaporation, condensation and heat generation which is mainly due to chemical oxidation. Numerical results were compared with experimental measurements, showing excellent agreement.
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