Monte Carlo Method For High Temperature Thermal Radiation Transport Simulation

Since the random simulation method,Monte Carlo method was proposed,it had been having a wide application.With a great improvement of science technology and computer,Monte Carlo method obtains more attention.To some extent,Monte Carlo method can substitute a part of physical experiments and it can solve some difficulties that deterministic method can hardly solve,which makes it a useful and powerful tool in nuclear physical experiments.There can reach up to tens of millions of degrees Kelvin in the Inertial Confinement Fusion.In this extreme condition,thermal radiation which is emitted from material is the major way of energy transport.However,because the interactions between thermal radiation and material are much too complicated and radiation transport equation is nonlinear,deterministic method can not obtain an accurate result.Thus Monte Carlo method is the best choice to solve the radiation transport problem.Implicit Monte Carlo(IMC)is a common method that is used in the simulation of thermal radiative transport.IMC can correctly simulate the radiation transfer processes in material.In material with high opacity,however,the simulation efficiency become very low,which will cost too much computational resource.In this paper,at first,the process of source particle sampling method of IMC in spherically symmetric geometry is investigated and a new sampling method is put forward.The new sampling method can amend the deviation result from the particle sampling.Second,based on IMC,a one-dimensional grey Discrete Diffusion Monte Carlo(DDMC)method is proposed.Then a FORTRAN code,DDMC radiation transfer simulation code is developed to solve the problem in which IMC spends too much computation time to simulate the material with high opacity.Subsequently,a method is investigated to correctly treat the hybrid of IMC and DDMC in 1-D slab/spherical geometry.Correspondingly,a method that can treat the interface between IMC region and DDMC region is proposed and a radiative simulation code of hybrid Monte Carlo Method is developed to solve the problem that DDMC result of boundary does not agree with physics.Also the code can overcome the defect that DDMC method will yield a low accurate result in low opacity material.In practice,for a system with both high opacity and low opacity material,DDMC will be conducted in high opacity region and IMC will be conducted in low opacity region and these two regions will be compounded by the interface treatment method in order to fulfill an efficient and accurate simulation of thermal radiation transport.To verify the new sampling method of source particle,thermal radiative transfer problems of spherical geometry are tested,which shows that the new sampling method can yield the more accurate results.To verify the efficiency and accuracy of DDMC method and hybrid radiative transfer simulation code,this paper conducts several simulation for typical radiative transfer in 1-D flat/spherical geometry.The result shows that in the simulation with high opacity material the code can yield a result corresponding with IMC and greatly raise the simulation efficiency.The efficiency can reach 29.2 in 1-D slab DDMC simulation and reach 8.6 in spherically symmetric DDMC simulation.The result also shows that in the simulation with both high and low opacity material the hybrid Monte Carlo method can also yield the same result comparing with IMC method and raise the simulation efficiency.The efficiency can be raised up to 10.6 in 1-D slab IMC-DDMC simulation and up to 3.6 in spherically symmetric IMC-DDMC simulation.