Four semi-implicit discretization schemes are used to construct preconditioners.And preconditioned Jacobian-free Newton-Krylov (JFNK) are presented to solve one-dimensional problems.Numerical results show that the preconditioning methods improve the convergence behavior of JFNK method dramatically.

A numerical method is developed for two-dimensional nonequilibrium radiation diffusion equations.Discontinuous Galerkin method is applied in spatial diseretization in which numerical flux is constructed with weighted flux averages.Implicit-explicit integration factor method for time discretization is applied to nonlinear ordinary differential equations which is obtained with discontinuous Galerkin method. Radiation diffusion equations with multiple materials are solved on unstructured grids in numerical tests.It demonstrates that the method is effective for high nonlinear and tightly coupled radiation diffusion equations.

We discuss numerical simulation of one-dimensional non-equilibrium radiation diffusion equations.A weighted numerical flux between adjacent grid cells is obtained by solving heat conduction equation with discontinuous coefficient.With this numerical flux of diffusive generalized Riemann problem(dGRP),a discontinuous finite element method is proposed for radiation diffusion equations. A backward Euler time diseretization is applied for semi-discrete form and a Picard iteration is used to solve nonlinear system of equations.Numerical results demonstrate that the method has a capability of capturing strong gradients and can be accommodated to discontinuous diffusion coefficient.

We discuss numerical simulation of one-and two-dimensional nonlinear Schrödinger (NLS) equations (NLS).With numerical flux of diffusive generalized Riemann problem,a direct discontinuous Galerkin (DDG) method is proposed.L² stability of the DDG scheme is proved and it is shown that it is a conservative numerical scheme.The one-dimensional case indicates that the DDG scheme simulates various kinds of soliton propagations and it has excellent long-time numerical behaviors.Two-dimensional numerical results demonstrate that the method has high accuracy and is capable of capturing strong gradients.

We construct a Runge-Kutta discontinuous Galerkin (RKDG) finite element method for two-dimensional compressible gas dynamic equations in Lagrangian coordinate.The equations for fluid dynamics and geometry conservation laws are solved simultaneously.All calculations can be done on fixed meshes.Information of grid velocities are not needed in calculation.Several numerical examples are used to evaluate efficiency and reliability of the scheme.It shows that the algorithm works well.

K-V beam through an axisymmetric uniform-focusing channel is studied in a particle-core model.Beam halo-chaos is observed and a soliton function controller is proposed based on halo formation and the control of halo-chaos.A multiparticle simulation to control the halo by a soliton function controller is performed.It shows that the halo-chaos and its regeneration can be eliminated.