High-Order Linear Discontinuous and Diamond Differencing Schemes Along Cyclic Characteristics

We are investigating a new class of linear characteristics schemes along cyclic tracks for solving the transport equation for neutral particles with scattering anisotropy. These algorithms rely on linear discontinuous exact integration and diamond differencing, as implemented with the method of discrete ordinates. These schemes are based on linear discontinuous coefficients that are derived through the application of approximations describing the mesh-averaged spatial flux moments in terms of spatial source moments and of the beginning-of-segment and end-of-segment flux values. The linear discontinuous characteristics (LDC) and quadratic-order diamond differencing (DD1) schemes are inherently conservative. In this technical note, we intend to continue the development of the LDC and DD1 schemes by extending their application to cyclic trackings. This extension will make possible the representation of reflective or general albedo boundary conditions. We will present an improved and much shorter derivation of the LDC and DD1 schemes, compared to a previous presentation. Finally, we will implement the new schemes as Matlab scripts for solving a one-dimensional slab benchmark and in the DRAGON5 lattice code for solving a more representative two-dimensional eight-symmetry pressurized water reactor assembly mock-up.