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Computational Investigation of Buoyancy Influenced Flows and Benchmarking exercise Presenter: Yacine Addad (PDRA) (KNOO Team: D. Laurence, M. Cotton, A. Keshmiri, S. Rolfo) (Collaborators: S. Benhamadouche, R. Howard, F. di Mare) School of Mechanical, Aerospace & Civil Engineering (MACE) The University of Manchester 7th Int. ERCOFTAC Symposium-ETMM7- 4-6 June 2008,Limassol, Cyprus
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AGR working scheme The Heated pipe: Relevance to AGR and VHTR
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RANS models predictions buoyancy aiding
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Results for Fully-Developed Forced Convection. (no buoyancy) Expt. of Polyakov & Shindin
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Test Case Description Re=180 based on R and u . Boussinesq Approximation. Periodic Flow. Lz=30R Grid1: 1.61 million Grid2: 4.83 million Grid1 Resolution: r + min =1.0, + =6.28, z + =18. Grid2 Resolution: r + min =1.0, +=6.28, z+=7.03. Buoyancy effects on turbulence in VHTR channels: WR-LES
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Nusselt number as a function of the buoyancy parameter from You et al. For RANS models predictions, see the paper by Amir Keshmiri et al. Ratio of SGS to molecular viscosity
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Case1: Forced convection Gr/Re 2 =0.0 Buoyancy effects on turbulence in VHTR channels: WR-LES Data normalized by the bulk velocity
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Cases from Gr/Re 2 =0.063 to Gr/Re 2 =0.241 Buoyancy effects on turbulence in VHTR channels: WR-LES Data normalized by the bulk velocity
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NEARLY-HORIZONTAL SHALLOW CAVITY TEST CASE Ra= 4.16 10 8 NCELL= 3 million Boussinesq approximation Pr=0.71 (Air) =5° LES Grid (Case1) 0.8h Plan Y-Z
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NEARLY-HORIZONTAL SHALLOW CAVITY TEST CASE LES RESULTS Q=0.05
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NEARLY-HORIZONTAL SHALLOW CAVITY TEST CASE LES RESULTS
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NEARLY-HORIZONTAL SHALLOW CAVITY TEST CASE RANS RESULTS Low-Re. models tested: k- Lien et al. (1996) k- Wilcox (1998) k- SST Menter (1993) v 2 -f Lien & Durbin (1996) Buoyancy term included in k-equation thermal fluxes
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Energy conservation: Taylor-Green vortices test case.
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Taylor-Green vortices test case: mesh generation. Resolution: 60 x 60 Time step: 0.01 => CFL max < 0.2
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Effects of the velocity/pressure coupling
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Comparison between the codes for RR=0.75 (6/8) RR=0.75 6/8
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N xNyNz LES68 to 2004642 to 100 DNS256193192 Re=395 Domain 2 2 LES Ncells= 443,272 DNS Ncells = 9,486,336 (Ref: Moser et al. 1999) Channel flow test case
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Channel flow test case: Mean Velocity predictions
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Channel flow test case: Reynolds Stresses
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Budgets of the Reynolds stress components Ref: T. Omori et al. Int. J. Heat and fluid flow 2008
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Viscus diffusion term Dissipation term Channel flow test case: Budget for k
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Budget for k STAR: Grid (141x184x177) = 4.59 million DNS : Grid (256x193x192)= 9.48 million
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STAR: Grid (141x184x177) = 4.59 million DNS : Grid (256x193x192)= 9.48 million Budget for uu
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STAR: Grid (141x184x177) = 4.59 million DNS : Grid (256x193x192)= 9.48 million Budget for vv
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STAR: Grid (141x184x177) = 4.59 million DNS : Grid (256x193x192)= 9.48 million Budget for ww
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STAR: Grid (141x184x177) = 4.59 million DNS : Grid (256x193x192)= 9.48 million Budget for uv
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Conclusions Acknowledgements: TSEC programme 'KNOO' EPSRC funding under grant EP/C549465/1 for PDRA and Computer resources
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