Conservative Interpretation of Nonconservative Discrete Ordinates Radiative Intensity Distribution

The discrete ordinates interpolation method (DOIM) and the finite element discrete ordinates method (FEDOM) show good accuracy and versatility for calculation of radiative intensity. However, these methods are nonconservative since the intensity is computed only at grid points without considering control volume. When these methods are to be used together with a finite volume-based code for fluid flow and transport analysis, intensity at the center of control volume or surface, whichever is missing, needs to be calculated, and the control volume photon balance should be evaluated. For this reason, the method of satisfying control volume photon balance, without sacrificing the accuracy, is critically discussed first. Based on this rationale, the supplementary DOIM (SDOIM) is proposed to calculate the missing intensity. In addition, the integration method of RTE (IMRTE), used in DOM or FVM to satisfy the control volume photon balance, and linear interpolation method (LIM) are also examined to compare with the SDOIM. The accuracy, physical reliability and smoothness of the intensity obtained by using the three methods are carefully analyzed. Application of the SDOIM shows reliable results which are accurate and free from physically unrealistic intensity distribution.