scholarly journals Computational Study of Compartment Size Effects on Backdraft Intensity

2021 ◽  
Vol 35 (1) ◽  
pp. 11-19
Author(s):  
Su-Im Ha ◽  
Chang Bo Oh ◽  
Bit-Na Baek
Keyword(s):  
Computational Study ◽  
Combustion Model ◽  
Fire Dynamics ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Air Mixing ◽  
Fast Chemistry ◽  
The Moment ◽  
Inside Wall ◽  
Previous Experimental Study

A computational study was performed to evaluate the effects of compartment size on backdraft intensity. The compartment sizes were selected such that each direction was enlarged by a factor of 2, 2.5, 2.625, and 3 based on the reduced-scale compartment of a previous experimental study. A fire dynamics simulator was used for the computation, and a large eddy simulation and a mixing-controlled fast chemistry combustion model were adopted. Results revealed that the overall equivalence ratio defined by the amounts of fuel inside the compartment and oxygen induced from the opening had similar values at the moment when the air reached the inside wall. The fuel–air mixing inside the compartment was found to be achieved more rapidly with a decreased compartment size. The peaks of pressure and heat release rate inside the compartment increased with an increase in compartment size. However, these peaks were found to increase exponentially with an increase in the ratio of the compartment volume and opening size, and the correlation showed a very high R-squared value.

scholarly journals A Fractal Dynamic SGS Combustion Model for Large Eddy Simulation of Turbulent Premixed Flames

2016 ◽  
Vol 188 (9) ◽  
pp. 1472-1495 ◽  
Author(s):  
Katsuhiro Hiraoka ◽  
Yuki Minamoto ◽  
Masayasu Shimura ◽  
Yoshitsugu Naka ◽  
Naoya Fukushima ◽  
...  
Keyword(s):  
Large Eddy Simulation ◽  
Premixed Flames ◽  
Combustion Model ◽  
Turbulent Premixed Flames ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Turbulent Premixed

Dissipation in Implicit Turbulence Models: A Computational Study

2003 ◽  
Author(s):  
L. G. Margolin ◽  
P. K. Smolarkiewicz ◽  
A. A. Wyszogrodzki
Keyword(s):  
Numerical Simulation ◽  
Preliminary Analysis ◽  
High Reynolds Number ◽  
Computational Study ◽  
Turbulence Models ◽  
Finite Volume Methods ◽  
Data Set ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

We describe a series of computational experiments that employ nonoscillatory finite volume methods to simulate the decay of high Reynolds number turbulence. These experiments cover a broad range of physical viscosities and numerical resolutions. We have extracted a data set from these experiments detailing the energy dissipation by physical viscosity and by the numerical algorithm. We offer a preliminary analysis of this data, including new insights into the (computational) transition between direct numerical simulation and large eddy simulation.

The Germano Large Eddy Simulation Model Used for the Simulation of Separated Flow

2003 ◽  
Author(s):  
Engin Cetindogan ◽  
Govert de With ◽  
Arne E. Holdo̸
Keyword(s):  
Reynolds Number ◽  
Large Eddy Simulation ◽  
Computational Study ◽  
Separated Flow ◽  
Local Flow ◽  
Large Eddy Simulation Model ◽  
Slip Boundary ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Les Model

A computational study of unsteady, separated fluid flow was made using the Large Eddy Simulation (LES). As flow problem the turbulent flow past a circular cylinder at a Reynolds number of Re = 3900 was chosen. The objective of this work was to study the numerical and modelling aspects of the dynamic Germano-LES turbulence model. Before LES can be used for applications of practical relevance, such as the flow around a complete aircraft or automobile, extensive tests must be carried out on simpler configurations to understand the quality of LES. Also, the influence of different grid resolutions was examined. Due to the fact of a low Reynolds number, no-slip boundary conditions were used at solid walls. Two different subgrid scale models were applied. In recent years several simulations were carried out using the Smagorinsky-LES model but there is still a lack of experience using the dynamic Germano-LES model, which takes the local flow parameters into account. Several simulations with different parameters and grid-models were carried out both with the Germano-LES model and the Smagorinsky-LES model. Comparisons were made between these two models as well as with several experimental data taken from literature.

Dissipation in Implicit Turbulence Models: A Computational Study

2006 ◽  
Vol 73 (3) ◽  
pp. 469-473 ◽  
Author(s):  
L. G. Margolin ◽  
P. K. Smolarkiewicz ◽  
A. A. Wyszogradzki
Keyword(s):  
Numerical Simulation ◽  
Preliminary Analysis ◽  
High Reynolds Number ◽  
Computational Study ◽  
Turbulence Models ◽  
Finite Volume Methods ◽  
Data Set ◽  
Eddy Simulation ◽  
Large Eddy ◽  
High Reynolds

We describe a series of computational experiments that employ nonoscillatory finite volume methods to simulate the decay of high Reynolds number turbulence. These experiments cover a broad range of physical viscosities and numerical resolutions. We have extracted a data set from these experiments detailing the energy dissipation by physical viscosity and by the numerical algorithm. We offer a preliminary analysis of this data, including new insights into the (computational) transition between direct numerical simulation and large eddy simulation.

Large Eddy Simulation of an Enclosed Turbulent Reacting Methane Jet With the Tabulated Premixed Conditional Moment Closure Method

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Carlos Velez ◽  
Scott Martin ◽  
Aleksander Jemcov ◽  
Subith Vasu
Keyword(s):  
Turbulent Combustion ◽  
Moment Closure ◽  
Scalar Dissipation ◽  
Combustion Model ◽  
Conditional Moment ◽  
Eddy Simulation ◽  
Conditional Moment Closure ◽  
Major Species ◽  
Large Eddy ◽  
Closure Method

The tabulated premixed conditional moment closure (T-PCMC) method has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes in Reynolds-averaged Navier–Stokes (RANS) environment by Martin et al. (2013, “Modeling an Enclosed, Turbulent Reacting Methane Jet With the Premixed Conditional Moment Closure Method,” ASME Paper No. GT2013-95092). Here, the premixed conditional moment closure (PCMC) method is extended to large eddy simulation (LES). The new model is validated with the turbulent, enclosed reacting methane backward facing step data from El Banhawy et al. (1983, “Premixed, Turbulent Combustion of a Sudden-Expansion Flow,” Combust. Flame, 50, pp. 153–165). The experimental data have a rectangular test section at atmospheric pressure and temperature with an inlet velocity of 10.5 m/s and an equivalence ratio of 0.9 for two different step heights. Contours of major species, velocity, and temperature are provided. The T-PCMC model falls into the class of table lookup turbulent combustion models in which the combustion model is solved offline over a range of conditions and stored in a table that is accessed by the computational fluid dynamic (CFD) code using three controlling variables: the reaction progress variable (RPV), variance, and local scalar dissipation rate. The local scalar dissipation rate is used to account for the affects of the small-scale mixing on the reaction rates. A presumed shape beta function probability density function (PDF) is used to account for the effects of subgrid scale (SGS) turbulence on the reactions. SGS models are incorporated for the scalar dissipation and variance. The open source CFD code OpenFOAM is used with the compressible Smagorinsky LES model. Velocity, temperature, and major species are compared to the experimental data. Once validated, this low “runtime” CFD turbulent combustion model will have great utility for designing the next generation of lean premixed (LPM) gas turbine combustors.

scholarly journals Prediction of a Small-Scale Pool Fire with FireFoam

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Camilo Andrés Sedano ◽  
Omar Darío López ◽  
Alexander Ladino ◽  
Felipe Muñoz
Keyword(s):  
Numerical Results ◽  
Pool Fire ◽  
Flame Height ◽  
Combustion Model ◽  
Small Scale ◽  
Average Temperature ◽  
Eddy Simulation ◽  
Fire Experiment ◽  
Large Eddy ◽  
Good Agreement

A computational model using Large Eddy Simulation (LES) for turbulence modelling was implemented, by means of the Eddy Dissipation Concept (EDC) combustion model using the fireFoam solver. A small methanol pool fire experiment was simulated in order to validate and compare the numerical results, hence trying to validate the effectiveness of the solver. A detailed convergence analysis is performed showing that a mesh of approximately two million elements is sufficient to achieve satisfactory numerical results (including chemical kinetics). A good agreement was achieved with some of the experimental and previous computational results, especially in the prediction of the flame height and the average temperature contours.

Numerical Simulation of Cloud–Clear Air Interfacial Mixing: Homogeneous versus Inhomogeneous Mixing

2009 ◽  
Vol 66 (8) ◽  
pp. 2493-2500 ◽  
Author(s):  
Miroslaw Andrejczuk ◽  
Wojciech W. Grabowski ◽  
Szymon P. Malinowski ◽  
Piotr K. Smolarkiewicz
Keyword(s):  
Time Scale ◽  
Numerical Data ◽  
Droplet Evaporation ◽  
Direct Numerical Simulations ◽  
Heuristic Argument ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Air Mixing ◽  
Scale Ratio ◽  
Bin Microphysics

Abstract This note presents an analysis of several dozens of direct numerical simulations of the cloud–clear air mixing in a setup of decaying moist turbulence with bin microphysics. The goal is to assess the instantaneous relationship between the homogeneity of mixing and the ratio of the time scales of droplet evaporation and turbulent homogenization. Such a relationship is important for developing improved microphysical parameterizations for large-eddy simulation of clouds. The analysis suggests a robust relationship for the range of time scale ratios between 0.5 and 10. Outside this range, the scatter of numerical data is significant, with smaller and larger time scale ratios corresponding to mixing scenarios that approach the extremely inhomogeneous and homogeneous limits, respectively. This is consistent with the heuristic argument relating the homogeneity of mixing to the time scale ratio.

Development of Wall-Adapting Local Eddy Viscosity Model for Study of Fire Dynamics in a Large Compartment

2013 ◽  
Vol 444-445 ◽  
pp. 1579-1591
Author(s):  
A.C.Y. Yuen ◽  
G.H. Yeoh ◽  
R.K.K. Yuen ◽  
S.M. Lo ◽  
T. Chen
Keyword(s):  
Eddy Viscosity ◽  
Scale Model ◽  
Subgrid Scale ◽  
Fire Dynamics ◽  
Rotation Rates ◽  
Eddy Simulation ◽  
Eddy Viscosity Model ◽  
Large Eddy ◽  
Scale Turbulence ◽  
Spatial Locations

The Wall Adpating Local Eddy Viscosity (WALE) subgrid-scale turbulence model was adopted for an in-house large eddy simulation (LES) fire code in which the turbulence is fully coupled combustion and radiation models. The traditional Smagorinsky subgrid-scale model accounts only strain rate of the turbulent structure while the WALE model considers both the strain and the rotation rates. Furthermore, the WALE model automatically recovers the near wall-scaling for the eddy viscosity hence more adaptive for wall bounded flows.A 15 m long test hall fire was reconstructed by the in-house fire code with 1.5 MW fire source. The performance of the WALE model was assessed by comparingpredicted transient gas temperatures and velocities at various spatial locations.

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