CFD V&V Workshop for CFD V&V Benchmark Case Study. ASME 2015 V&V Symposium

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2 CFD V&V Workshop for CFD V&V Benchmark Case Study ASME 2015 V&V Symposium ASME V&V 30 Committee Las Vegas, Nevada May 14, 2015

3 CFD V&V Workshop Why are we here? Goals CFD V&V Benchmark Case Study

4 State of V&V/UQ for M&S Over 30 years of V&V/UQ research and development Philosophy, Theory, Methods, Demonstrations, Applications Standards, Guides, and Best Practices Advanced the State-of-the-Art V&V/UQ in practical industrial/engineering settings V&V/UQ R&D not reflected in State-of-the-Practice Methodology and procedures for code and solution verification are fairly well developed, but poorly practiced Methodology for validation experiments has been developed, but rarely conducted Little or no use of systematic/standardized frameworks for assessing predictive capability Need: Transition V&V/UQ from R&D to mainstream practice, especially for industry

5 Approach Taken: CFD V&V Benchmark Case Study The purpose of the CFD V&V Workshop is to bring together experimenters, CFD analysts and methods developers together in an open forum of exchange of ideas and collaboration to define a CFD V&V Benchmark Case Study that with active participation of CFD researchers and practitioners in government, academia, and industry could advance the state-ofthe-art and - practice in V&V and UQ of CFD modeling and simulations.

6 Goals for this Workshop Provide venue for open forum discussions about the needs and requirements for conducting a V&V benchmark case study Prediction + Uncertainty Credibility Assessment V&V Strategy Help define a V&V benchmark case study Models & Codes Experiments & Measured Data Quantities of Interest Final Analysis and Reporting Add to community s experience with V&V and UQ Initiate a V&V Workshop Series

7 CFD V&V Workshops 2015 Workshop Planning and defining the first benchmark case study Call for participation will be released in the summer/fall of 2015 Detailed description of the benchmark case study and how one can participate 2016 Workshop Presentations from benchmark case study participants Invited Talks Results, Findings and Lessons Learned 2017 Workshop and Beyond Focus on Use Cases and the roles that V&V and UQ will play in enabling use cases Identifying and developing compelling use cases for CFD

8 CFD V&V Workshops A long-term, sustained effort that will be affiliated with the ASME V&V Symposium Integration of enabling supporting components ASME V&V and UQ Journal Publication and documentation of workshop activities and initiatives Dissemination of knowledge gained and lessons learned Important for sustained V&V and UQ research and development and continued participation of academics and researchers Nuclear Energy Knowledge base for Advanced Modeling and Simulation (NE-KAMS) DOE Office of Nuclear Energy sponsored effort in knowledge management for modeling and simulation Archival repository for V&V and UQ data and information in support of V&V and UQ assessments and R&D Facilitates sharing and collaboration

9 The CFD V&V Benchmark Case Study Opportunity Statement Upper plenum mixing in Sodium-cooled Fast Reactors (SFR) Case Study: Turbulent Mixing of Parallel Jets in Water Background and Theory Validation Experiment: UTK Twin Jet Water Facility Facility engineered and fabricated at UTK, early 2013 Testing performed at UTK and now at Texas A&M Validation Data: Twin Jet Water Facility Experimental Setup & Data PIV data and Ultrasonic Doppler data Data sets (both UTK and Texas A&M) CFD Analysis Turbulent flow behavior of 3-D Twin Jets

10 Opportunity Statement SFR upper plenum thermal hydraulics opportunities [Tenchine (2010)]

11 Opportunity Statement (Cont.) CFD simulations can aid in the thermal and hydraulic analysis for safety & design Validation of CFD code is needed before it can replace lumped-parameter models [Lomperski and Pointer (2013)] TRIO_U CFD results for SFR core exit temp. and velocity [Tenchine (2010)]

12 Turbulent Submerged Jets Homogeneous fluid continuously injected into quiescent fluid Strictly momentum driven (no buoyancy effects) Neglect heat dissipation due to viscous molecular effects -> momentum is constant for any given cross-section Submerged jet diagram [Tschaepe (2011)]

13 Parallel Submerged Jets Three regions converging, merging, and combined Experiments by Elbanna et al. on turbulent air jets showed higher turbulence in combined region compared to single jet Previously there have been no PIV data sets for parallel water jets reported in the literature Parallel jet flow characteristics [Anderson and Spall (2001)]

14 Validation Experiments Verification - compare computational result to numerical and/or analytical solutions Validation - compare computational result to experimental data Fundamentally unique class of experiment in which the code is the customer [Abernethy et al. (1985)] Primary goal of the experiment is to assess the accuracy of simulation result Boundary conditions must be well characterized Effort must be made to separate the bias error and the random error

15 Errors in Validation Experiments Total error made up of bias error and random error: δκ = β + ϵκ Quantification of the bias error helps expose irregularities involved with the testing facilities or experimental conditions [Abernethy et al. (1985)].

16 PIV Validation Experiment Example: ANL MAX Validation Experiment MAX test section showing vertical velocity components [Lomperski and Pointer (2013)]

17 Twin Jet Water Facility Past and Present UTK Texas A&M

18 Twin Jet Water Facility Flow Field Data for Validation Typical PIV Image Plane Thermal Stratification Test

19 PIV Experiment Setup PIV experiment setup at UTK

20 Twin Jet Water Facility Experiments Data Sets Table 4.1: PIV Data Set Overview File Numbers Description t(µs) 0-99 Above jet (20mm offset) Above jet (no offset) Above jet (parallel plane) Above jet (parallel plane) Above jet (125 mm offset) Above jet (125 mm offset) Above jet (175 mm offset) Above jet (175 mm offset, parallel plane) Above jet (175 mm offset, parallel plane) Lower jet and entrainment region Lower jet and entrainment region (parallel plane) Lower near-field entrainment region Lower near-field entrainment region, off-center Lower near-field entrainment region, off-center Far field Far field Far field Far field Far field Far field Entrainment region Single data field, Single Jet, Example, 29,000 fields archived

21 TJWF Validation Data Sets PIV results (above-jet)

22 TJWF Validation Data Sets Comparison with UVP data TJWF UVP data [Wiggins and Ruggles (2014)].

23 TJWF Validation Data Sets Turbulence Intensity

24 TJWF Validation Data Sets Errors in the combined region

25 CFD Analysis of TJWF Modeling Setup - Geometry Required simplifications including: Jet Stagnation Tanks Region below Jets Weir Overflow

26 CFD Analysis of TJWF Modeling Setup Boundary Conditions Boundary Type Value Surface List Velocity Inlet 0.75 m/s 1 and 2 Pressure Outlet 0 Pa 3 Wall Boundary - 0

27 CFD Analysis of TJWF Modeling Setup Convergence Parameters The following residuals were monitored for a reduction of 3-4 orders of magnitude to declare convergence: Momentum in the X, Y, and Z directions Continuity Turbulent Kinetic Energy and Dissipation

28 CFD Analysis of TJWF Results Velocity Contours The velocity contour plot shows two characteristics of the twin jets: The Combined Jet Development and Decay Negative Pressure/Converging Region

29 CFD Analysis of TJWF Results Centerline Static Pressure Negative to positive pressure region (Z/a ~ 0 to 15) Pressure decays in combined region from Z/a ~ 15 to 120.

30 CFD Analysis of TJWF Results Centerline Velocity Negative centerline velocity in combining region (Z/a ~ 0-5) Rapid buildup in velocity from Z/a ~ 5-20 Slow decay from Z/a ~

31 CFD Analysis of TJWF Results Converging Velocity Profiles Two distinct jets are observed near outlets At Z/a = 30, one jet is observed with the highest centerline velocity

32 CFD Analysis of TJWF Mesh Independence Study Centerline Static Pressure Medium: 12 million cells Fine: 25 million cells Very Fine: 45 million cells

33 CFD Analysis of TJWF Mesh Independence Study Centerline Static Velocity Medium: 12 million cells Fine: 25 million cells Very Fine: 45 million cells

34 Workshop Agenda Invited Presentations to establish a proper context and focus the open forum discussions to follow Validation Benchmarks Bill Oberkampf V&V Assessments Chris Roy ASME V&V and UQ Journal Ashley Emery NE-KAMS Weiju Ren Open Forum Discussions

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