Wielandt Iteration Combined with Multi-Group GMRES for Accelerating Matrix MOC Convergence

In the Matrix MOC, a linear algebraic equation system can be constructed by sweeping only once, and then solving the linear system takes the place of repeatedly characteristics sweeping. Traditionally, keff is computed by power iteration（PI）, whose convergence rate depends on the dominance ratio deeply. Large problems of practical interest often have dominance ratios close to 1, leading to slow convergence of PI. Combined with multi-group GMRES coupling all groups directly, Wielandt iteration is studied for accelerating Matrix MOC. Numerical results of several benchmarks demonstrate that Wielandt iteration combined with multi-group GMRES can obtain good accuracy and higher efficiency compared with PI.