An HLLC-type approximate Riemann solver is proposed to simulate one-dimensional elastic-perfectly plastic flow with Wilkins model. This Riemann solver introduces plastic wave and has the same wave number with actual physics. The wave speed is determined by characteristic analysis of wave system. The algorithm is simple to implement and does not need iteration. In order to reduce wall heating error in the simulation for strong shock (or rarefaction), wall heating viscosity is designed to effectively suppress the non-physical wall heating phenomenon.

In cell-centered Godunov method,unphysical overheating problem exists in rarefaction flows.We develop a Godunov method with staggered Lagrangian discretization which is applicable to isentropic flows. Velocity and thermodynamic variables are defined in staggered discretization. The velocity averaging process in a cell is avoided,so that the kinetic energy dissipation due to the momentum averaging process is removed. In contrast to the traditional von Neumann staggered grid method, the face flux is provided by a node multidimensional Riemann solver. The difficulty in selecting multidimensional artificial viscosity is overcome. In order to reduce unphysical entropy production of multidimensional Riemann solver in rarefaction problems,we give a reasonable criterion of rarefaction appearance to satisfy the thermodynamic relation. Numerical results show that the method removes overheating problem in rarefaction problems, and retains the property of accurate shock capturing of the original Lagrangian Godunov method as well.

To solve unsteady laminar flow problems,a method of velocity-stress-pressure formulation instead of velocity-vorticitypressure formulation is developed.With Newton's linearized method to linearize convective terms and preconditioned conjugate gradient method to solve equations,unsteady stress formulation of Navier-Stokes equations is solved.Comparison between numerical and experimental results of cavity laminar flow shows that result of stress formulation fits experiment better and has higher accuracy than vorticity formulation.The stress formulation can deal with subgrid stress with least squares finite element method.Comparison with experimental results of cavity turbulent flow reveals feasibility of the method.It lays a firm foundation for large eddy simulation computation.

A new adaptive lattice Boltzmann model is presented to simulate super-sonic flows. Particle velocities may have a large range of values. The support set of equilibrium distributions is determined by the mean velocity and internal energy. The adaptive nature of particle velocities permit the mean flow to have a high Mach number. A particle potential energy is introduced to make the model suitable for the perfect gas with arbitrary specific heat ratio. Navier-Stokes equations are derived by the Chapman-Enskog method from the BGK Boltzmann equation. As numerical test, the simulation is performed for a flow passing over a forward-facing step at Mach number 3 on a hexagonal lattice. The shocks are well captured.

A multispecies,multispeeds lattice Boltzmann model is presented to study the mass diffusion properties.The diffusion equations are derived by the Chapman-Enskog method.The one dimensional simulations for the sinusoidal concentration distributions are compared with the theoretical results,showing good agreement.The numerical simulations for 2-D convection diffusion problems are also presented.

In this Paper the finite eclment-finite difference method is used to solve numerically two problems of 15-degree and 45-degree one-way wave equations For 15-degree one-way wave equation we have obtained the seismic profile when linear elements and quadratic elements are used, It has been proven that the linear element method is the Claerbout difference method.

The one-dimensional hydrodynamic code SSS for shock and detonation wave propagation in inert and reactive media is described in this paper. The elastic-plastie-hydrodynamic model and four burn techniques, the Arrhenins law,C-J volume, sharp shock and Forest Fire are used. There are two options of the equatin of sta te for detonation products:HOM and JWL. Compared with it's reference-the SIN code published by LANL, the SSS code has several new options:laser effects, blast waves, diverging and instantantaneous detonation waves with arbitrary initiatron positions. Two examples are given to compare the SSS and SIN calculations with the experimental data.

In this paper a mathematical model for the extraction-injection of geothermal reservoir in multiple wells is developed, It silplidies a complicated tridimentionsl heat conduction problem to a bi-dimentional one, The latter is a problem of coupling equations, one of wbich is a one-dimentional heat conduction equation in vertical, and another is a one-dimentional convection-conduction eqyation in horizontal, It deduces several different schemes for coupling solutions as the differential equations are discrtized, and discusses the procecdure of computation, We have prepard the software for drwing the groundwater has been exploited with double wells, three wells and five wells.