1. EdF meeting 18 May 2009 Review of all the work done under the framework of Code_Saturne by S. Rolfo School of Mechanical, Aerospace & Civil Engineering (MACE) The University of Manchester Manchester, M60 1QD www.CFDtm.org

2. Summary  Use of unstructured meshes in Code_Saturne:  Taylor Green vortices  Laminar Channel flow  Developments:  Hybrid RANS/LES  Calculation of statistics: store of gradients (need only feedback)  Refined LES of flow in fuel rod bundle arranged into a triangular array  Sodium Fast Reactors (SFR) fuel bundles.

3. Energy conservation: Taylor-Green vortices test case.

4. Taylor-Green vortices test case: mesh generation. Resolution: 60 x 60 Time step: 0.01 => CFL max < 0.2

5. Effects of different Refinements Ratio (RR)‏

7. Refinements 1-2 optimization.

8. Map of 1-2 optimization

9. Example of optimization. P1P3

10. In terms of energy conservation the tilting is not producing the best results. The best results are obtained keeping the interface flat. Moving the position of the interface does not affect to much the results. Results optimization

11. Global error on U and dU/dx for different meshes

12. Error conformal mesh

13. Error RR=0.97 mesh

14. Error RR=0.75 mesh

15. Error RR=0.50 mesh (base)

16. Error RR=0.50 mesh (“optimal” P3)

17. Error Hybrid mesh poly+hexa

18. Laminar channel flow poly mesh Test of laminar flow at Ret=50 1.Mesh for Ret=395 1.N cells: 639000 2.N Faces: 3660000 3.Different type of optimization, no big improvements (no reducing of warping, skewing angle, etc) 4.Interface prism/poly @ y+~100=>interface @ y=0.18 2.Mesh for Ret=1020 1.N cells: 3500000 2.N Faces: 20500000 3.Interface prism/poly @ y+=100=>interface @ y=0.1 In both the cases relatively big oscillation of V, W, P were found. Moreover the maximum velocity at the centre line was 20 or less. (Ret=50 => Umax=25). This means a difficulty of the mesh to converge.

19. Laminar channel flow mesh 395 ( History)

20. Laminar channel flow mesh 395 (Profile)

21. Laminar channel flow mesh 1020 ( History)

22. Laminar channel flow mesh 1020 (Profile)

23. Rod Bundle arranged in a triangular array Geometrical configuration:  P/D = 1.06  Big computational domain (7 mil cells) Thermal Hydraulic regime  Re=5994  Heat transfer (q w =60 W/m2) New cases to run  Re=5994 with imbalance in the temperature  Re=12000 (mesh ready with 14 mil cells)  Possible Higher P/D

24. Mean quantities

25. Re stresses

26. Temperature <uθ><uθ> <wθ><wθ> <vθ><vθ>

27. Imbalance of temperature

28. 28 SFR fuel assembly: Case presentation Flow parameters: P/D = 1.1 Re = 11000 (Bulk vel = 1 m/s) Working fluid liquid sodium  = 847 kg/m3 µ = 2.55 10 -4 Kg/m/s Pr = 5 10 -3

29. SFR test case

30. SFR rod bundle  Future near work  Calculation of the complete geometry with 271 pins (mesh ready, but problem with some warp faces).  Literature review on experimental paper of the same geometry with different numbers of fuel elements.  Future work  Extension of the 6 pin mesh in order to perform low Reynolds calculations.  Extension of the case to different number of pins and comparison of the results with the available experiments  Refined calculations: LES?!!

31. RANS-LES coupling (1)‏ The Hybrid RANS-LES method is following a usual LES decomposition in large scale and sub-grid part: The anisotropic part of the residual stress tensor and residual heat flux can be decomposed following a Schumann decomposition: Sub- grid viscosity RANS viscosity computed from the mean velocity field For the eddy conductivity a simply turbulent Prandtl number analogy is used

32. RANS-LES coupling (2) The merging between the two velocity fields is done through a blending function to obtain a smooth transition Turbulent RANS length scale computed with a relaxation model based on Filter width Empirical constants computed in order to match the stress profile for channel flow @ Re = 395

33. RANS-LES Results

34. Gradient calculation.  Gradient calculation and store in PROPCE  Now available only for the velocity and version 1.4.0  Addition of pressure and temperature really straight forward  Possible use to compute budgets, but extension in order to include second order derivatives is necessary => huge number of properties will be stored  Need a feedback about the implementation in order to carry out the addition of all the others term.