DRAFT IMECE2005-82993 MONTE CARLO SCHEMES FOR RADIATIVE TRANSFER IN MEDIA REPRESENTED BY PARTICLE FIELDS

Monte Carlo ray-tracing schemes are developed for the eval-uation of radiative heat transfer for problems, in which the par-ticipating medium is represented by discrete point-masses, such as the ow eld and scalar elds in PDF Monte Carlo methods frequently used in combustion modeling. Photon ray tracing in such cases requires that an optical thickness is assigned to each of the point-masses. Two approaches are discussed, the Point Particle Model (PPM), in which the shape of particle is not spec-ied, and the Spherical Particle Model (SPM) in which particles are assumed to be spheres with constant radiation properties. An-other issue for ray tracing in particle elds is the inuence region of a ray. Two ways of modeling a ray are proposed. In the rst, each ray is treated as a standard volume-less line. In the other ap-proach, the ray is assigned a small solid angle, and is thus treated as a cone with a decaying inuence function away from its center line. Based on these models, three dierent interaction schemes between rays and particles are proposed, i.e., Line-SPM, Cone-PPM and Cone-SPMmethods, and are compared employing sev-eral test problems. Nomenclature A cylindrical shell I emission intensity; particles enclosed by ray L thickness of gas slab; side-length of computational do-main Q emi total energy emitted from a particle Address all correspondence to this author. R particle inuence radius; gas constan