摘要:

AbstractParallelization of the Porsching algorithm for the numerical integration of hydraulic network conservation equations is described, and a theoretical analysis of the performance of the parallelized algorithm on a MIMD-type parallel computer is given. It is shown that good speedup and efficiency of parallel processing can be achieved by using a quasi-MIMD mode of operation employing (a) a master/slave configuration of processors, (b) message passing for data communication, (c) global synchronization of all processors before data communication, (d) a simple time-shared bus with data broadcast facility as the interconnection network, and (e) distributed communication memories for data communication.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23620

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractMixed convection flow for parallel vertical channels connected at upper and lower plenums is studied. The one-dimensional conservation equations are formulated in dimensionless form using channel integral parameters. Based on this formulation, expressions are derived for stable flow and reversal of channel flow. The equations are then used to calculate the flow redistribution within a liquid-metal reactor core during natural circulation primary loop flow. A channel/plenum interaction phenomenon, which limits the applicability of using one-dimensional formulations, is modeled, and a correlation is formulated utilizing measured results to predict the onset of this behavior. Finally, the reversal of a heated channel from upflow to downflow, which cannot be predicted with a onedimensional analysis, is described, and the channel/plenum interaction previously modeled is proposed as the mechanism that initiates this flow reversal.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23621

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe streaming term in the transport equation is expressed in arbitrary geometry. It is shown that explicit and relatively simple results are obtained if one uses the surface geometry of the body under consideration to define the polar and azimuthal angles describing the unit vector of propagation. In particular, the local normal and principal directions of the surface play an important role in these considerations. The results for the streaming term are expressed in both gradient and divergence form.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23622

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractAn S2synthetic acceleration scheme is developed for the one-dimensional Snequations (slab and sphere) with linear discontinuous spatial differencing. A Fourier analysis shows that the scheme is unconditionally stable for a model problem. Computational results demonstrate the effectiveness of the technique for varying cell thickness and scattering anisotropy.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23623

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractModifications to the computational scheme of the existing slab geometry gamma-ray transport code ASFIT are introduced to facilitate the inclusion of coherent scattering contributions. The revised code is tested with two model problems and subsequently is used to investigate quantitatively the transport effects of coherent scattering as a function of the incident photon energy and the atomic number Z of the medium. The shield materials studied in this respect are beryllium, aluminum, iron, molybdenum, tin, tungsten, lead, and uranium, and the incident photon energies range between 0.015 and 0.3 MeV. The system studied is a 48-mfp-thick slab, embedding a thin strip of isotropic source located 4 mfp from the left boundary. Plane parallel incident fluxes have also been studied in certain instances. The results of the computation are presented in the form of scattered flux spectra and dose rates, both at several depths inside the media. Tables of point isotropic source buildup factors including coherent scattering are also presented.It is observed that the addition of coherent scattering does not alter the shape of the flux spectrum significantly, but changes only the magnitude. Except for a small distance near the source, these changes in flux and hence dose are downward at all depths, becoming appreciable at large depths. Furthermore, the magnitude of the reduction varies essentially according to the ratio of the coherent scattering to the total cross section (ΣR/Σt)

ISSN:0029-5639    

DOI:10.13182/NSE89-A23624

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractSeveral existing methods for the assessment of the sensitivity of output uncertainty distributions generated by deterministic computer models to the uncertainty distributions assigned to the input parameters are reviewed and new techniques are proposed. Merits and limitations of the various techniques are examined by detailed application to the suppression pool aerosol removal code (SPARC).

ISSN:0029-5639    

DOI:10.13182/NSE89-A23625

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractAn analytical expression for calculating the disadvantage factor in a heterogeneous slab cell is derived by solving the one-speed neutron transport equation using a one-term scattering kernel (isotropic scattering). The expression derived is based on the method of spatial expansion developed by Pomraning and Clark. The numerical results appear to be very good compared with the other high-order approximate and exact methods.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23626

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor