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International Heat Transfer Conference 16

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

TWO-STEP ITERATIVE METHOD FOR RADIATIVE TRANSFER CALCULATIONS IN AXISYMMETRIC FLAMES CONTAINING ABSORBING AND SCATTERING PARTICLES

Leonid A. Dombrovsky
Joint Institute for High Temperatures, 17A Krasnokazarmennaya Str., Moscow, 111116, Russia; Tyumen State University, 6 Volodarsky Str., Tyumen, 625003, Russia

Siaka Dembele
Fire, Explosion and Fluid Dynamics Research Group, School of Mechanical and Automotive Engineering, Kingston University, London SW15 3DW, UK

Jennifer X. Wen
Faculty of Engineering, Kingston University, Friars Avenue, Roehampton Vale, London, SW15 3DW, United Kingdom; School of Engineering, University of Warwick, Coventry CV4 7AL, UK

Ivan Sikic
School of Engineering, University of Warwick, Coventry CV4 7AL, UK

DOI: 10.1615/IHTC16.cat.023303
pages 1581-1587


KEY WORDS: Radiation, Computational methods, Large-scale open flames, Two-step method

Abstract

The discrete ordinates and finite volume methods used in most fire simulations codes for radiative transfer calculations suffer from high computing overheads. A procedure based on two-step iterative method is suggested to simplify time-consuming spectral radiative transfer calculations in open flames containing scattering particles. At the first step of the problem solution, the P1 approximation is used to calculate the divergence of radiative flux, and it is sufficient to determine the flame parameters. The second step of solution is necessary to obtain the radiation field outside the flame, and this can be made independently using the ray-tracing procedure and the transport source function determined at the first step. Such a splitting of the complete problem results in much simpler algorithm than those used traditionally. It has been proved in previous papers that the combined two-step method is sufficiently accurate in diverse engineering applications, especially in the scattering media. At the same time, the computational time decreases in about two orders of magnitude as compared with direct methods. An axisymmetric pool fire suppressed by a water spray is considered as the case problem in the present paper to analyze the effect of radiation scattering by evaporating water droplets. The strong effect of scattering on radiative power field in the flame is obtained computationally for the first time.

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