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KNOO Annual Meeting 2008

LES and URANS of Turbulent Flow parallel to PWR and AGR Fuel Rod

Bundles

S. Rolfo

The University of Manchester, M60 1QD, UKSchool of Mechanical, Aerospace & Civil Engineering.

CFD group

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RNR-Na assembly (Super Phoenix Reactor).

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Scales separation and levels of approximation.

DNS

LES

RANS

Scales separation and levels of approximation.

Fixed point at which the FFT is evaluated

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Code_Saturne

Code developed by EdF and now open source downloadable from:

http://rd.edf.com/the-edf-offers/research-and-development/softwares/code-

saturne-107008.html

Unstructured

Co-located, Finite Volume Formulation

Different turbulent models (both RANS and LES)

Incompressible or expandable flows with or without heat transfer

Different modules: radiative heat transfer, combustion, magneto-hydrodynamics, compressible flows, two-phase flows

Possible coupling with Code_Aster for structural analysis and with Syrthes for thermal analysis.

Parallel code coupling capabilities (awarded the Gold medal on HPCx)

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Rod Bundle arranged in a triangular array

• Two different geometrical configuration

1. P/D = 1.06

2. P/D = 1.15

• Three different Thermal Hydraulic regimes:

1. P/D = 1.06 @ Re = 6000 with heat transfer (LES)

2. P/D = 1.06 @ Re = 36000 with heat transfer (RSM-URANS)

3. P/D = 1.15 @ Re = 6000 with heat transfer (LES)

A’A

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Flow Pulsation in the mid-plane (P/D = 1.06)

LES @ Re = 6000

URANS @ Re = 39000

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Flow Pulsation in the mid-plane (P/D = 1.06)

URANS

LES

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Power spectra

P/D =1.06 LES @ Re = 6000

Point A Point B

P/D =1.15 LES @ Re = 6000

Point B

P/D =1.06 URANS @ Re = 36000

Point A

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Average Field (LES P/D = 1.06 Re = 6000)

<U> <T>

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Reynolds Stress

<uu>

<vv>

<ww>

<uv>

<uw>

<vw>

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Conclusions and future workFlow Fluctuations in the mid plane of the geometry were successfully detected

for the configuration characterised by P/D = 1.06. However P/D = 1.15 did not show any significant behaviour from channel or pipe flows.

URANS is able to capture the flow fluctuations, however the Reynolds stresses are more similar to those observed at higher P/D.

LES, at low Re number, of larger geometry (two complete sub-channels) to be tested in order to verify the correct prediction of the dominant frequency.

Improved geometry with the addition of a wire, wrapped around the pin (SFR assembly), will be computed.

AcknowledgementsAcknowledgements This work was carried out as part of the TSEC programme KNOO and as such we are

grateful to the EPSRC for funding under grant EP/C549465/1.