摘要:

Particle methods are now commonly used in the numerical simulation of problems arising in Plasma Physics. They consist in replacing the plasma by a “large” set of charged superparticles which obey the usual Physics laws and then in computing the interactions of these superparticles. For a detailed description of the particle methodology in Plasma Physics, we refer to Hockney and Eastvood [11].

ISSN:0041-1450    

DOI:10.1080/00411458608210442

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The exit distribution problem for one speed isotropic radiative transfer in an inhomogeneous slab can be solved in terms of an analog of the Chandrasekhar H-Function. This function is the solution to a nonlinear integral equation in two variables for one group problems and in more variables for multi-group problems. In this paper we give algorithms for vector computers, in particular the CDC Cyber 205, that make it practical to solve such equations.

ISSN:0041-1450    

DOI:10.1080/00411458608210443

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Parallelization of standard multigroup methods used to solve the linear (Boltzmann) tranaport equation in the discrete ordinates (Sn) representation and coupled chaotic iteration schemes are the focus of this analyais. On the Denelcor HEP, we extend two serial iteration schemea, categorize speedup, and contrast ordered and chaotic methods. Ordered and chaotic iteration atrategies, with arid without acceleration, support relatively unreatricted paralleliam and appear to be robust parallel techniques. Parallel modifications and recoding efforts to seriol iteration algorithms are straightforward, actual speedup and efficiency are high, and payoff appears substantial, largely due to the coarse computational granularity of the multigroup technique. Chaotic schemes also converge faster than ordered strategies.

ISSN:0041-1450    

DOI:10.1080/00411458608210444

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

We are pursuing a study of new numerical methods used to solve the x, y geometry discrete ordinates neutron transport equation. For both Ckl characteristic and Nklnodal methods, the angular flux is approximated by a polynomial of total degree k inside each mesh cell and by polynomials of degree l along the cell edges.

ISSN:0041-1450    

DOI:10.1080/00411458608210445

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A separation of variable method is proposed for the analysis of spatial differencing schemes for discreate-ordinates problems. This method leads to the defination of a “spectrum” for the differencing scheme which is a function of the cross sections and the spatial mesh. An analysis of the spectrum as a function only of the mesh yields theoretioal results rgarding stability, positivity, and accurancy which have not been obtained previousty. In this paper, we apply the theory to the standard dimond differences scheme and a new extended diamond difference scheme. Numerical results obtained from the solution of discrete-ordinates problems using these two schemes are shown to be in excellent agreement with the spectral theory.

ISSN:0041-1450    

DOI:10.1080/00411458608210446

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Numerical errors of PALLAS calculation due to special mesh size sare examined for a typical deep penetration shielding problem of isotropic incident fission neutrons penetrating a 200-cm-thick water slab. The exponential approximation for the source spatial distribution to solve the transport equation based on the direct integration method is verified to be effective for radition transport in attenuating medium, while the linear approximation employed in the old PALLAS code is found to produce large errors for calculations with large mesh sizes.

ISSN:0041-1450    

DOI:10.1080/00411458608210447

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A novel method, the discrete cones method (DCN), is proposed as an alternative to the discrete ordinates method (SN) for solutions of the two-dimensional neutron transport equation. The new method utilizes a new concept, discrete cones, which are made by participating a unit spherical surface that the direction vector of particles covers. In this method particles in a cone are simultaneously traced instead of those in discrete directions so that an anomaly of the SN method, the ray effects, can be eliminated. The DCNmethod has been formulated for X-Y geometry and a program has been created by modifying the standard SNprogram TWOTRAN-II. Our sample calculations demonstrate a strong mitigation of the ray effects without a computing cost penalty.

ISSN:0041-1450    

DOI:10.1080/00411458608210448

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The flux (r,Ω) at locationrin the direction of unit vectorΩis expanded as a series of the form

ISSN:0041-1450    

DOI:10.1080/00411458608210449

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A newly developed discrete ordinate method of solution of differential equations is applied to the solution of the Fokker-Plank equation employed in the a nalysis is of optical bistability. The solution is written in terms of the eigenfunctions of the Fokker-PlancK operator and the time evolution of the probability density function is studied. The present analysis includes a study of the convergence of the eigenualues and eigen functions for different choices of the quadrature rule upon which the discrete ordinate method is based.

ISSN:0041-1450    

DOI:10.1080/00411458608210450

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Under suitable physically reasonable assumptions, stability and convergence results are obtained for the upwind finite-difference approximation in energy to the Spencer-Lewis equation of electron transport.

ISSN:0041-1450    

DOI:10.1080/00411458608210451

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor