Fluid Dynamic Modeling And Verification Of The 3D GASFLOW Code

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1 Fluid Dynamic Modeling And Verification Of The 3D GASFLOW Code Z. Xu, W. Breitung, T. Jordan, P. Royl, J. Travis Forschungszentrum Karlsruhe International workshop On Passive Safety Systems in Advanced PWRs (IPASS) Shanghai Jiaotong University, Shanghai, China April 28-30, 2008 IPASS, Shanghai, April

2 CONTENTS Motivations Governing equations Numerical approach H 2 models for severe accidents Mitigation measures Online diagnostic criteria for H 2 combustions in different regimes User interface Preprocessing Post-processing Model verifications Laminar flow 1D Diffusion Advection diffusion Turbulent model Criteria of H 2 combustion regimes H 2 mitigation Current activities Summary IPASS, Shanghai, April

3 Motivations Disadvantages of old tools lumped parameter codes Lumped parameter models suffer from coarse space resolution Risk is dominated by in-homogeneities and should be resolved for predictive H 2 analysis in severe accidents Difficult to defend for a H 2 problem in nuclear plant Example 1 Example 2 Example 3 IPASS, Shanghai, April

4 Example 1 Motivations GKN-2 SB-LOCA Vol,% Wasserstoff Magere Verbrennungsgrenze Max. H 2 Durchschn. H 2 Mit Rekos Temperatur (K) Ohne Rekos T max Vol,% Dampf Zeit, s Comparison between GASFLOW (CFD, FZK) and RALOC / COCOSYS (LP, GRS) IPASS, Shanghai, April

5 Example 2 Motivations HDR Test E11.2: GASFLOW Simulation and LP Results IPASS, Shanghai, April

6 Example 3 Motivations H 2 (820 kg) distribution in containment at 8000 s in EPR-study for SB-LOCA IPASS, Shanghai, April

7 Mass equations - Total mass - Species α Governing equations t t Momentum equation t ( ) ρdv = ρ b u AdS + S ρ dv V S ρ α dv = ρ α ( b u) AdS ( J α A)dS + S ρ dv V ρudv = ρu ( b u ) AdS pds + ρg V Energy equation t S S S V V s dv ( τ A)dS + ( D d A)dS + S M dv ρidv = ρi ( b u ) p V h2 o AdS p( u A)dS dv ( q A)dS V t + S I dv V S S S V S s V V V IPASS, Shanghai, April

8 IPASS, Shanghai, April Governing equations Turbulent κ-ε model ( ) [ ]dv S T ds : ( dv t V S V = κ κ κ ρε μα τ κ σ μ ρκ ρκ g A u u b ( ) dv S C T C ds : C ( dv t V S V = κ ε ε κ ε ρ μα κ ε τ κ ε ε σ μ ρε ρε g A u u b

9 Numerical approach Mesh cell serves as control volume in the three-phase finite-volume method Phase A: Explicit Lagrangian phase -> source terms Combustion and recombination Mass and energy transfer Interspecies diffusion Pressure boundary conditions Gravitational body forces Viscous stress tensor Effects of reduced cell-faced areas Effects of distributed "sub-grid" structures Phase B: Implicit Lagrangian phase -> determine time-advanced pressure Simultaneous solution of time-advanced pressure, density, velocity, and internal energy Phase C: Rezone phase -> advection terms Repartition mass, momentum, and energy to original grids GASFLOW took 70 man-years (20 in LANL and 50 in FZK) for code development and applications IPASS, Shanghai, April

10 H 2 models for severe accidents Mitigation measures Igniter, single cell model in GASFLOW Recombinor (Siemens, NIS), recombinor model in GASFLOW Sump (steam source), homogeneous sump model in GASFLOW CO 2 / N 2 dilution (post-accident), additional species in GASFLOW IPASS, Shanghai, April

11 H 2 models for severe accidents Online diagnostic criteria for H2 combustions in different regimes enable GASFLOW to make risk evaluations and to predict the property of H 2 -air mixture Flammability Slow deflagration σ-criteria Fast deflagration λ-criteria Deflagration to Detonation Transition (DDT) IPASS, Shanghai, April

12 User interface Preprocessing Ongoing work on GUI development Program of grammar error-check for input deck Post-processing Flexible netcdf data format Applicable processing programs: AVS, GMV, OCTAVE, OpenDX, Tecplot, Example IPASS, Shanghai, April

13 Example User interface > 20% Dampf Rekombinator > 10 % Wasserstoff Rekos T > 550K Without igniter P.Royl, FZK IRWST EPR full containment in SB-LOCA T>1000K With igniter P.Royl, FZK IPASS, Shanghai, April

14 Model verifications Laminar flow y A 2D laminar incompressible flow between two parallel stationary walls, driven by a constant body force caused by gravity The momentum diffusion and the gravity term are validated in the momentum conservation equation w(y) GASFLOW analytische Lösung IPASS, Shanghai, April

15 1D diffusion of H 2 into air Model verifications Species diffusion model is validated by the 1D diffusion problem Molenbruch Wasserstoff Mole fraction of H 2 GASFLOW analytische Analytical Lösung solution t=10s Cell Zellnummer number (10 cm) IPASS, Shanghai, April

16 Model verifications 2D advection diffusion of N 2 into air Mass fraction Gasflow,2s Gasflow,4s Gasflow,6s Gasflow,8s Gasflow,10s GFM,2s GFM,4s GFM,6s GFM,8s GFM,10s Mass fraction GFM,4.00s GFM,4.25s GFM,4.50s GFM,4.75s GFM,5.00s GFM,5.25s GFM,5.50s GFM,5.75s GFM,6.00s Gasflow,4.00s Gasflow,4.25s Gasflow,4.50s Gasflow,4.75s Gasflow,5.00s Gasflow,5.25s Gasflow,5.50s Gasflow,5.75s Gasflow,6.00s u(x, y,t) x, cm In advection direction (y=0) In transverse direction (x=10cm) t (x Vτ) Vx (x + Vτ) y y 1 y y 0 = (x Vτ)exp + (x + Vτ)exp erfc erfc dτ 3 64πDτ 4Dτ D 4Dτ 0 4Dτ 4Dτ y, cm IPASS, Shanghai, April

17 Model verifications Turbulent model verifications Turbulent flow in rectangular channel 1 GASFLOW Experiment Comparison between GASFLOW simulation, data and theoretical solution of Spalding 159 equidistance cells in channel width of 18 cm U / U o U Re=228,000 T = 295 K P = 1 bar Re=228,000 T = 295 K P = 1 bar Uo = 1066 cm/s U* = 44 cm/s y / D GASFLOW Experiment Spalding 10 Uo = 1066 cm/s U* = 44 cm/s y + IPASS, Shanghai, April

18 Model verifications Turbulent model verifications Decaying turbulent flow in rectangular channel U=6.55 m/s Monitor locations x/m: y 90 y-z view z x M=1 inch k 0 = m 2 /s 2 10 k 0 = m 2 /s 2 k, m 2 /s ε 0 = m 2 /s 3 Experiment (Wells&Stock) GASFLOW, Cell Size = 1 inch Numerical-Xu, Cell Size = 1 inch Analytical ε, m 2 /s 3 1 ε 0 = m 2 /s 3 Experiment (Wells&Stock) GASFLOW, Cell Size = 1 inch Numerical-Xu, Cell Size = 1 inch Analytical X, inch X, inch IPASS, Shanghai, April

19 Model verifications Turbulent model verifications Turbulent flow in parallel plates, 20 C, 1 bar, channel width 18 cm 8 Experiment Re= k(m2/s2) 4 GASFLOW y/d IPASS, Shanghai, April

20 Model verifications Turbulent model verifications BMC-Test-Jx7: He jet into air, 42 m/s, 200 s duration 20 He Konzentration (Vol%) He Konzentration (Vol%) KP000K76 FZK/GASFLOW Zeit (s) 6KP270M18 FZK/GASFLOW Zeit (s) R5 R6 Ring - room raum R9 R Vol Vol % He He Iso-Oberfläche ISO-surface He-Quelle He-source He Konzentration (Vol%) He Konzentration (Vol%) FZK/GASFLOW 6kp270M Vertikale Entfernung vom Injektionsort (m) x EXPERIMENT FZK/GASFLOW x x x x x 0 x x Entfernung von der Jet-Achse (m) x x IPASS, Shanghai, April

21 Model verifications Turbulent model verifications Turbulent heat transfer Air U m = 1341 cm/s T m = 600 K T w = 330 K Measure Plane 1.6 cm o Data GASFLOW, 41 cells T w = 870 K T (K) cm 200 cm y / H o Data GASFLOW, 41 cells U / U m o Data GASFLOW, 41 cells ) ρ ( g /c 3 m y / H y / H IPASS, Shanghai, April

22 Model verifications Turbulent model verifications Turbulent heat transfer with condensation 9.69 m/s, 400K, bar 50% air, + 50% steam 1060 cm T = 300K w T =300K w 1200 cm Measure plane 18 cm 30 a 30 b u + 20 u + u +, T + & C T + C + u +, T + & C T + C IPASS, Shanghai, April y a: 9 cells in width b: 39 cells in width y +

23 Model verifications Criteria of H 2 combustion regimes σ-criteria Expansion ratio σ (= ρ ub /ρ b ) 7 global quenching quenching-reignition FZK choked flames quasi-detonation 6 KI FZK KI 5 FZK KI FZK 4 KI T ~ 300 K fast flames FZK / KI σ = 3.75 slow flames unstable flames Tube diameter L / Laminar flame thickness δ x 10-3 different length scales L FZK FZK / KI KI FZK-tube: 350 mm RUT : 2400 mm Driver tube: 174 mm Torpedo tube : 520 mm δ ~ 0.1 mm IPASS, Shanghai, April

24 Model verifications Criteria of H 2 combustion regimes λ-criteria D Geometrical size D, mm IPASS, Shanghai, April

25 entlangdervertikalenmitelinie Model verifications Radiation model 2D problem 0.8 T c along vertical middle line T 4* T 4* T c T c L y y T h T 4* = (T 4 -T 4 c ) / (Th 4 -Tc 4 ) L / λ = 1 Exact solution of transport equation o GASFLOW simulation y* = y / L y IPASS, Shanghai, April

26 Model verifications An example of integral validation of GASFLOW HDR test E11.2: test conditions and pressure from old and new GASFLOW simulation IPASS, Shanghai, April

27 Current activities Pre- & post- processing program developing Parallelization SARNET ICEFUEL Dust PANDA THAI Non-nuclear application International cooperation IPASS, Shanghai, April

28 Summary Ground fluid dynamic models and, specially, hydrogen mitigation models are developed and verified for GASFLOW code Specific hydrogen models enable GASFLOW to predict hydrogen behaviors in nuclear containment during severe accidents GASFLOW offers reliable predictions of hydrogen distributions with mitigation in quite complex 3D geometries IPASS, Shanghai, April

29 Thank you! Are you interested in > 20% Dampf GASFLOW Workshop in China in Autumn 2008? > 10 % Wasserstoff Rekos T > 550K If yes, please put your name in the list near the poster. Details and further announcement in P.Royl, FZK Tips: no registration fee. IPASS, Shanghai, April