Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Otaka, Masahiko; Ohshima, Hiroyuki; Ninokata, Hisashi;
PNC TN9410 96-212, 36 Pages, 1996/06
A single phase subchannel analysis code ASFRE-III has been developed at PNC for predicting behavior of coolant and fuel pin temperature distributions in a fast reactor fuel subassembly under various operation and accident conditions such as a local flow blockage event. Salient features of the code are: a distributed resistance model of wire-wrap spacers, a porous blockage model, and an efficient matrix solver suitable for a large vector/parallel computation. In this study, ASFRE-III was applied to the thermal-hydraulic analysis of the two out-of-pile experiments using sodium performed at PNC for the purpose of the code validation. The one was performed around rated flow and heat flux conditions and the other was decay heat removal conditions. The computational results obtained under various flow and heat flux conditions were compared with the experimental data. The predicted coolant temperatures in subassemblies were agreed well with the measured data within 5 
6% in the wide range from low to high Reynolds number regions.
PNC TN9410 92-105, 65 Pages, 1992/04
A thermal striping phenomenon characterized by a random temperature fluctuation occurs in the region immediately above the FBR core due to the temperature difference of the core outlet coolant between subassemblies. In this study, a direct numerical simulation code DINUS-3(Direct NUmerical Simulation using 3rd order upwind scheme) has been developed based on the third order upwind scheme and investigated applicability of the DINUS-3 code to temperature fluctuation analysis. From the analysis of von Karman vortex streak behind a rectangular obstacle, the following results have been obtained: (1)Change of the vortex frequency (the strouhal number St) with increase of the Reynolds number Re can be estimated by the DINUS-3 code. (2)A stationary random turbulence fluctuation including a buffer region between the transition and the turbulent regions can be predicted using the DINUS-3 code. And the followings became clear after the analysis of a nonisothermal parallel jet experiment using water. (1)A temperature fluctuation phenomenon including complicated frequency components can be simulated well using the DINUS-3 code. (2)Calculated dominant frequency has shown good agreement with the experiment. From the analysis, it is concluded that the DINUS-3 code based on the third order upwind sheme has a sufficiently high potential in providing good interpretation of experimental results related to the temperature fluctuation phenomena such as thermal striping.
JAE HO*;
PNC TN9410 91-196, 64 Pages, 1991/07
There are many arguments on the empericalconstants of the turbulence models becausetheir ariginal values are selected on thebasis of the dimensional analysis.Especia-lly,the particular model form of the gene-ration -destruction terms in the transpo-rt equation for the turbulent kinetic ene-rgy dissipation rate 
has been treated asa source of the arguments.Having recogniz-ed the cause for sensitivities of calcula-tions on the relevant constants,this studycould be performed to evaluate the applic-ability of the turbulence models adoptedadopted in AQUA to relatively slow flowsthrough analyses of a typical thermal cav-ity problem and the 7th IAHR benchmark pr-oblem featuring many aspects of the pheno-mena predicted during the natural circula-tion decay heat removals in the FBR react-or vessel.Despite the level of handled tu-rbulence models,such as the standard 
&two-equation model and the algebraic stre-ss/flux model,the calculation results arefairly sensitive to the varitions of thepe
