Journal of Quantitative Spectroscopy & Radiative Transfer 93 (2005) 125–137 Identification of appropriate source models for accurate diffusion modeling of radiative transfer in a non-absorbing foam layer Matthew R. Jones à , Vladimir P. Solovjov, Brent W. Webb, Shaun M. Salisbury Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602-4201, USA Received 1 February 2004; accepted 1 July 2004 Abstract The diffusion approximation is used to model the propagation of radiation scattered from a pulsed laser beam incident on a non-absorbing foam layer. Various mathematical models for the source term are considered, and integral transforms are used to solve the differential equation. Comparison of the calculated reflectance profiles with the results of Monte Carlo simulations indicates that careful selection of the source model leads to improved results. Diffusion theory source models which provide accurate predictions for radiative transfer and the limits on their accuracy are identified. r 2004 Elsevier Ltd. All rights reserved. Keywords: Radiative transfer equation; Diffusion theory; Source models; Monte Carlo simulations 1. Introduction A promising method for characterizing turbid media such as foams is to measure the time- dependent local hemispherical reflectance of a pulsed or amplitude-modulated laser beam from a foam layer. Using an inverse algorithm, the radiative and thermophysical properties of the foam are estimated based on these reflectance measurements. As the inverse algorithm requires an efficient method for solving the forward problem, it is desirable to employ the diffusion approximation to model the propagation of the scattered radiation through the medium. A major ARTICLE IN PRESS www.elsevier.com/locate/jqsrt 0022-4073/$-see front matter r 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.jqsrt.2004.08.017 à Corresponding author. Tel.: 801-422-3070; fax: 801-422-0516. E-mail address: mrjones@et.byu.edu (M.R. Jones).