Two-Step Iterative Method for Radiative Transfer Calculations in Axisymmetric Flames Containing Absorbing and Scattering Particles

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 raytracing 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.

Models of Extinguishing Agent Movement in Air Space

“…В [1], а також в [2] наведені математичні моделі, які описують рух вогнегасної речовини в полум'ї пожежі. Для такого опису використовується традиційний підхід -математичні моделі, представлені у вигляді диференційних рівнянь.…”

A Review of Optical and Radiative Properties of Nanoparticle Suspensions: Effects of Particle Stability, Agglomeration, and Sedimentation

“…The majority of systems within this category are either porous in nature or contain particulates that actively participate in radiative transfer processes. Various examples of the particulate systems are fluidized and packed beds, fluidized bed and surface combustors, catalytic reactors, microsphere and fibrous insulations, ceramic foam insulations, ceramic and metallic screens, porous and sintered materials, particulate solar collectors, and liquid-droplet radiators, which are used in space applications (Viskanta and Mengüç, 1989;Dombrovsky and Baillis, 2010;Dombrovsky et al, 2018). Other examples where radiation from particles plays a significant role are a nuclear winter scenario, large-scale fires, and radiation transfer in the core debris of a melted reactor (Mengüç and Viskanta, 1986) or in a containment building and numerous others (Gupta et al, 2012;Dhand et al, 2015).…”