2018) Large eddy simulation of upward flame spread on PMMA walls with a fully coupled fluid-solid approach. Combustion and Flame, 190 . pp. 365-387. Permanent WRAP URL: Abstract A fully coupled fluid-solid approach has been developed within FireFOAM 2.2.x, a Large Eddy Simulation (LES) based fire simulation solver within the OpenFOAM® toolbox. Due consideration 1 Corresponding author email: Jennifer.Wen@warwick.ac.uk phenomena such as investigating the effects of width, inclination angles and side walls on flame spread as well as the predictions of flame spread in practical applications. Keywords Upward flame spread, Fully coupled fluid-solid approach, Large eddy simulation, PMMA 1. The time averaged reaction rate for the mass fraction equation chemical species J J ω is expressed as ( ) J J J u J fu f ( ) ( ) J J J

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We present a new combustion simulation technique based on a lookup table approach. In the proposed technique, a flow solver extracts the reaction rates from the look-up table using the mixture fraction, progress variable, and reaction time. Look-up table building and combustion simulation are carried out simultaneously. The reaction rates of the chemical species are recorded in the look-up table according to the mixture fraction, progress variable, and time scale of the reaction. Once the reaction rates are recorded, a direct integration to solve the chemical equations becomes unnecessary; thus, the time for computing the reaction rates is shortened. The proposed technique is applied to an eddy dissipation concept (EDC) model and it is validated through a simulation of a CO-H2-air nonpremixed flame. The results obtained by using the proposed technique are compared with experimental and computational data obtained by using the EDC model with direct integration. Good agreement between our method and the EDC model and the experimental data was found. Moreover, the computation time for the proposed technique is approximately 99.2% lower than that of the EDC model with direct integration.

A large eddy simulation of the turbulent syngas non-premixed jet flame of Sandia ETH/Zurich B is conducted using an in-house version of FireFOAM, a fire simulation solver within OpenFOAM. Combustion is modeled using (i) the newly extended eddy dissipation concept for the large eddy simulation published by the authors’ group, (ii) the 74-step CO–H2–O2 mechanism and (iii) the relatively simple tabulated chemistry approach. The effects of the nonunity Lewis number and thermal diffusion (=Soret diffusion) are considered in the mass fraction and enthalpy equations. Systematic validation and model sensitivity studies have been conducted against published experiments of the turbulent syngas diffusion flame from the international workshop on measurement & computation of turbulent flames (TNF workshop). The predictions were in very good agreement with the relevant experimental data. The axial position of peak H2O moved toward the nozzle direction owing to the different diffusion coefficients of H2. In the radial direction, the effect of thermal diffusion was observed at x/d < 20, whereas those of the nonunity Lewis number and difference in chemistry were found at x/d < 40. After considering the effects of the nonunity Lewis number and thermal diffusion, as well as the detailed reaction mechanisms, the results were slightly better than those obtained under previous numerical conditions.

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In this paper, we present a simple combustion simulation technique based on a look-up table approach. In the proposed technique, a flow solver extracts the solutions of the ordinary differential equations (ODEs) of the chemical equations from the look-up table using the mixture fraction, mass fraction of products, and time scale of the reaction. The look-up table is constructed during combustion simulation. Thus, prior calculation is not needed in the proposed technique. The solutions of the ODEs are saved in the look-up table at points where the mixture fraction, mass fraction, and time scale are similar to those in the look-up table. Once the data are recorded, a direct integration to solve the chemical equations becomes unnecessary, and the time required to compute the reaction rates is shortened. The proposed technique is applied to an eddy dissipation concept (EDC) model and is validated through a simulation of a H 2 turbulent non-premixed flame and a CH 4 partially premixed flame. The results obtained through the proposed technique are then compared with experimental data and computational data obtained using the EDC model with direct integration. We found a good agreement between our method and the EDC model. Moreover, although the proposed technique is simple, the computation time for our technique is faster than the in situ tabulation method (ISAT) and is approximately 99% lower than that of the EDC model with direct integration. IntroductionBecause of the rapidly increasing availability of computing technologies, numerical simulations of turbulent combustion have become one of the major methods to predict fundamental phenomena of turbulence, combustion, and their interactions. Many unsteady combustion simulations have been performed to study these phenomena (Sadiki, et al., 2006, Godel, et al., 2009, Moureau, et al., 2011. However, the unsteady simulations require a high computational cost compared with steady simulations. Furthermore, the simulations of turbulent combustion that includes detailed chemical mechanisms also requires the high computational cost because a reaction calculation involves n-dimensional ordinary differential equations (ODEs) that must be solved according to the number of chemical species.Several techniques have been developed to overcome this problem. For example, the in-situ adaptive tabulation (ISAT) (Pope, 1997, Yang and Pope, 1998, Singer and Pope, 2006 method is based on in-situ generation of a look-up table constructed by solving for the time evolution of species concentrations directly, and it overcomes many of the difficulties associated with pre-computed look-up tables. This method has been adopted in ANSYS FLUENT using the eddy dissipation concept (EDC) model (Magnussen, 1981, Magnussen, 1989, Gran and Magnussen, 1995a, 1995b, Magnussen, 2005 and the probability density function (PDF) model (Bilger, 1980, Fox, 2003. The method of intrinsic low-dimensional manifolds (ILDM) (Maas and Pope, 1992, Maas and Pope, 1994, Gicquel, et al., 2000 allows the automatic red...

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