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CFD Workshop on Test Cases, Databases & BPG for Nuclear Power Plants Applications, 16 July 2008.

CFD Workshop on Test Cases, Databases & BPG for Nuclear Power Plants Applications, 16 July 2008. CFD Quality & Trust: mixed and natural convection test cases. The University of Manchester. Yacine Addad School of MACE , University of Manchester.

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CFD Workshop on Test Cases, Databases & BPG for Nuclear Power Plants Applications, 16 July 2008.

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  1. CFD Workshop on Test Cases, Databases & BPG for Nuclear Power Plants Applications, 16 July 2008. • CFD Quality & Trust: mixed and natural convection • test cases The University of Manchester Yacine Addad School of MACE , University of Manchester 1

  2. The buoyancy-opposed wall jet(QNET-CFD Application challenge TA3 – case 1) • Non-buoyant case • buoyant case low aspect Velocity ratio • buoyant case high aspect Velocity ratio 2

  3. Exp Star – SmagoSaturne Dyn Saturne fine mesh Vertical (V) & Horizontal mean velocityprofiles 3

  4. Thermal hydraulics of reactors Mixed convection in co-axial pipes (Y. Addad PhD, M. Rabitt British Energy) Study the physics of the flow in the decay heat inlet pen Examine the LES solution of the code Star-CD for the natural/mixed convection cases. Validate further the analytical wall functions developed at University of Manchester by Gerasimov et al. 4

  5. Coaxial heated cylinder study • LES validation and parametric test cases: • Case1-Natural convection in square cavity (Ra=1.58  109) • Case2-Natural convection in annular cavity (Ra=1.8109) Exp.Ref. McLeod 89 • Case3- annular cavity single coaxial cylinder (Ra=2.381010) • Case4- annular cavity with 3 coaxial cylinders (Ra=2.381010) • Case5- Flow in a horizontal penetration (bulk Re=620,000). 5

  6. Natural Convection in coaxial cylinders CASE-3: Ra=2.3810E+10 Case 2: Ra=1.810E+9 SGS visc/Molecular visc.<1 CASE-4: Ra=2.3810E+10 6

  7. Coaxial Cylinder – effect of Prt and convection scheme Mean Temperature Y. Addad with Star-CD 7

  8. Coaxial Cylinder – effect of Prt and convection scheme Rms temperature fluctuations Prt = 0.9 + bounded convection scheme is OK Prt = 0.4 + CDS 8

  9. 3 Cylinders test case 9

  10. NEARLY-HORIZONTAL SHALLOW CAVITYTEST CASE LES Grid (Case1) • Ra= 4.16108 • NCELL= 3 million • Boussinesq approximation • Pr=0.71 (Air) • =5° Plan Y-Z 10 0.8h

  11. NEARLY-HORIZONTAL SHALLOW CAVITYTEST CASE LES RESULTS Q=0.05 11

  12. NEARLY-HORIZONTAL SHALLOW CAVITY TEST CASE In progress LES Grid (Case2) • Ra= 4.16108 • NCELL= 3 million (same grid) • Boussinesq approximation • Pr=0.71 (Air) • =15° Q=0.05(same value as Case1) 12

  13. Buoyancy aiding or opposing vertical pipe flow V gradient nearer wall => Turbulence decrease buoyancy opposing buoyancy aiding V gradient away from wall => Turbulence increase 13

  14. Buoyancy opposing vertical pipe flow RANS predictions 14

  15. Conclusions and future work • LES of Industrial flow • Complex geometry LES easier than smooth channel flow • Responds to Industry needs:Thermal stresses, fatigue, Acoustics, FIV (vibrations) • Cost-wise accessible when limited to sub-domain • (next step RANS-Embedded LES ) • Unstructured griding with professional software: • Flexibility • Possible Quasi-DNS near wall resolution at Medium Re numbers • 2nd order accuracy may be sufficient. • Further developments and validation needed: • More griding flexibility (total cell size control from pre-simulation RANS and/or coarse LES). • Further testing of Polyhedral cells for LES (advantage: Energy conservation). • Run a benchmark computations to compare LES predictions with different codes (in-house via commercial). 15

  16. List of Publications • A. Keshmiri, M.A. Cotton, Y. Addad, S. Rolfo, and F. Billard, [2008] “RANS and LES Investigations of Vertical Flows in the Fuel Passages of Gas-Cooled Nuclear Reactors”, 16th Int. Conf. on Nuclear Engineering, ‘ICONE16’. • A. Keshmiri, M.A. Cotton, Y. Addad, D.R. Laurence, and F. Billard, [2008] “Refined Eddy Viscosity Schemes and LES for Ascending Mixed Convection Flows”, Proc. 4th Int. Symp. on Advances in Computational Heat Transfer ‘CHT-08’. • Y. Addad, M. Mahmoodilari, and D. Laurence [2008] “LES and RANS Computations of Natural Convection in a Nearly-Horizontal Cavity” Proc. 4th Int. Symp. on Advances in Computational Heat Transfer, ‘CHT-08’. • Y. Addad, D. R. Laurence [2008] “LES for Buoyancy-Modified Ascending Turbulent Pipe Flow”, 7th International ERCOFTAC Symposium on Engineering Turbulence Modelling and Measurements (ETMM7) . • Y. Addad, D. Laurence, and M. Rabbitt [2006] “Turbulent Natural Convection in Horizontal Coaxial Cylindrical Enclosures: LES and RANS Models” Turbulence, Heat and Mass Transfer 5. • Addad Y., Benhamadouche S., and Laurence D. [2004] “The negatively buoyant wall-jet: LES database” Int. J. Heat fluid Flow 25, pp795-808. 16

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