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197

ENSI Erfahrungs- und Forschungsbericht 2011

ficulties to appropriately predict the thermal mixing

around the spacers were encountered, something

that is believed to be related to the constraint of

applying a single set of the turbulent multipliers for

the entire calculation domain.

Secondly, efforts undertaken in recent years to

implement the STAR-CCM+ CFD code for specific

types of NPP applications were continued. To start,

a validation of a STAR-CCM+ EPR vessel model

developed within the project was completed [15].

Moreover, STARS finalized its participation to the

OECD/NEA Vattenfall T-junction benchmark, aimed

at investigating the capabilities of state-of-the-art

CFD codes to predict temperature fluctuations on

pipe walls under flow mixing conditions and thus

related to thermal fatigue [16]. A wide range of so-

lutions were submitted to this «blind» benchmark,

including the STARS contribution as well as another

independent PSI solution. The figure of merits (FOM)

combining the organizer’s ranking coefficients of

the submitted solutions in terms of predicted veloc-

ity profiles and wall temperatures, are presented on

the left-hand side of Fig. 4 noting that the lower

the FOM, the «better» the code performance with

regards to predicting the two above-mentioned

physical parameters. These results indicate thus a

rather satisfactory and competitive performance of

the STARS STAR-CCM+ solution.

An assessment of boiling models implemented

in STAR-CCM+ for two-phase flow applications

was also continued on the basis of the PWR PSBT

benchmark. This revealed a substantial enhance-

ment in void predictions when applying the new

generation boiling models implemented in the

code [17]. Finally, significant efforts were under-

taken to validate STAR-CCM+ for the vessel mix-

ing experiments that were carried out at the RO-

COM facility within the framework of the OECD/

NEA PKL project. Some of the main results [18]

are shown on the right-hand side of Fig. 4. There,

the upper figure shows snapshots (after start of

injection) of the predicted velocity profiles for the

buoyancy-driven experimental test, characterized

by a higher mass flow rate and a 12% higher den-

sity in Loop 1 compared to the three other loops,

as well as for a sensitivity calculation assuming 0%

density difference. These results emphasize a much

more homogeneous redistribution of the flow

along the downcomer annulus when assuming no

density differences. Now for the buoyancy-driven

experiment, the calculated core inlet temperature

as function of time is compared to the measured

Figure 4:

STARS Results with

STAR-CCM+ for OECD/

NEA Single-Phase CFD

Benchmarks.

0 0.5 1 1.5 2 2.5 3 3.5 4

ONB / FLUENT

NRG / STAR-CCM+

ANL /Nek5000

AEKI / FLUENT

FNS / FLUENT

USNRC / FLUENT

FKG / FLUENT

PSI-STARS / STAR-CCM+

NSI / CABARET

AaltoU / OpenFOAM

KINS / CFX

SIA / CFX

EDF / SATURNE

UPV / CFX

TexasA&M / STAR-CCM+

FKG / OpenFOAM

IKE / FLUENT

HacettepeU / FLUENT

ASCOMP / TransAT

JNES / AFFR

FZD / CFX

GRS / CFX

PSI / FLUENT

ANL / STAR-CCM+

Tractebel / CFX

AthensU / CFX

PisaU / CFX

CNS / ModTurc_Clas-IST

Relative

Velocity

Magnitude

Analysis of Test

with 12% Density Difference

Calculation

with assumed 0% Density Difference

OECD/NEA Vattenfall T-Junction Benchmark

– Combined Figure-of-Merit of Participants

Solutions

OCED/NEA PKL-II ROCOM Mixing Experiments

STAR-CCM+ Modeling and Analyses

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Caple AUF900 Manual de usuario Pagina 199

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