Radiative Transfer Modeling Developed at Onera for Numerical Simulations of Reactive Flows

Radiative flux and power have to be calculated in many applications simulated using CFD, such as the prediction of pollutant emissions and the service life of aeroengine combustors, the design of thermal protection systems and ignition of solid propellant rocket motors, the design of spacecraft heat shields for atmospheric (re-)entries, and so on. In such configurations, the media are composed of gases (combustion products or plasma) and particles (soot, alumina, water droplets). Since the use of a line-by-line approach is not possible in industrial configurations, radiative
properties are computed with an approximate band model. For gas radiative properties, this model is formulated either in terms of the absorption coefficient or in terms of transmissivity. To deal with any kind of problems, the Monte Carlo method has been chosen to solve the integral form of the Radiative Transfer Equation (RTE) allowing the use of the two formulations of the gas radiative property model. For media that can be
dealt with using a model formulated in terms of the absorption coefficient, the Discrete Ordinates Method (DOM), that solves only the differential form of the RTE, has also been developed since it is reputed to consume less computation time than the Monte Carlo method. In this paper the fundamental relations of thermal radiation are first summarized. Then, both of the numerical methods and all the gas and particle radiative property models used at Onera to solve the RTE are described. Finally, some examples of typical applications studied at Onera with ASTRE (Monte Carlo) and REA (DOM) solvers are presented briefly.