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Perspectives from the TNF Workshop

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1 Perspectives from the TNF Workshop
Robert S. Barlow Combustion Research Facility Sandia National Laboratories Support by: DOE Offices of Basic Energy Sciences Multi-Agency Coordinating Committee on Combustion Research (MACCCR) Workshop on Next Steps in Using Combustion Cyberinfrastructure

2 Perspectives from the TNF Workshop* : Outline
Background History (>10 years) What, Why, Who, When Use of the web Past use Types of content Current status Future directions Expanded types of flames Expended types of data Expanded size of content What might Cyber Infrastructure do for TNF? Needed functionality Chicken-egg problem * International Workshop on Measurement and Computation of Turbulent Nonpremixed Flames

3 Validation of Models for Turbulence/Chemistry Interaction
TNF Workshop – Focus Validation of Models for Turbulence/Chemistry Interaction spray pressure scaling particulates kinetics complex geometry turb/chem practical combustion systems Simple Jet Piloted Bluff Body Swirl Progression of well documented cases that are consistent with to the range of current capabilities of current models

4 TNF Workshop – Basics Genesis (early 1990’s)
Incomplete experiments, poorly defined comparisons with computations Internet offered opportunity for rapid communication, collaboration, data sharing TNF1 in Naples (1996) established the ground rules Collaboration of experimental and computational researchers Core groups: Sandia, Berkeley, Cornell, TU Darmstadt, Imperial College, U Sydney Framework for detailed comparisons of measured and modeled results Identify gaps in data and models, define research priorities Emphasis on fundamental issues of turbulence-chemistry interaction Nonpremixed and partially premixed flames of simple fuels (H2, CO, CH4) Progression in complexity of flow field and kinetics Public (web-based) availability of data sets and comparisons Primary basis (so far)  point statistics from Raman/Rayleigh/LIF and LDV Naples Heppenheim Boulder Darmstadt Delft Sapporo Chicago Heidelberg 1996 1997 1998 1999 2000 2002 2004 2006

5 TNF Workshop – Themes “We emphasize that this is not a competition, but rather a means of identifying areas for potential improvements in a variety of modeling approaches.” “This collaborative process benefits from contributions by participants having different areas of expertise, including velocity measurements, scalar measurements, turbulence modeling, chemical kinetics, reduced mechanisms, mixing models, radiation, and combustion theory.” TNF8 Organizing Committee R.S. Barlow, R.W. Bilger, J.-Y. Chen, A. Dreizler, J. Janicka, R.P. Lindstedt, A.R. Masri, J.C. Oefelein, H. Pitsch, S.B. Pope, D. Roekaerts, and L. Vervisch.

6 Gallery of Turbulent Flame Examples
Figure 1 (Barlow, ProCI 2007) a, b Simple jet flames c, d Piloted jet flames e Bluff-body f Bluff-body/Swirl g Lifted flame in vitiated coflow h Opposed jet flame i Unconfined swirl flame j Enclosed swirl flame k Premixed low-swirl flame l Premixed swirl, bluff-body m Enclosed premixed swirl flame n Premixed jet in vitiated coflow

7 TNF Workshop – Current Mode of Operation
People 1 main organizer a few (~6) active members of the organizing committee loose ongoing scientific collaborations (roughly people in “clumps”) ~ 80 participants at each workshop (every 2 years) Budget no targeted funding for TNF Workshop activities Sandia (DOE/BES) pays for some admin. support TU Darmstadt has also contributed admin. support (SFB 568) Sponsorship used to reduce registration fees for faculty & students Web Contents: ( very simple site data sets (compressed ascii files) and submodels (chem, mixing, radiation) proceedings (PDF) bibliography total < 1GB (only point data; no 1D, 2D, 3D; no simulation data)

8 TNF Workshop – Web Issues

9 TNF3 Workshop (1998) – Classic results for Flame D
laser axis laser axis x/d =45 x/d =30 x/d =15 x/d =7.5 x/d = 2 Premixed Pilot Flame PDF, CMC, ILDM steady flamelet, …

10 TNF4 Workshop (1999) – Example Comparisons
T scatter plots Conditional means: T, O2, CO2, CO, H2O, H2, CH4, OH, (NO) Axial and radial profiles: U, u’, F, F’, T, T’

11 Current Status on Piloted Flames
Thorough parametric studies of model sensitivity in RANS/PDF Pope’s group at Cornell Combinations of different mixing models and mechanisms 100’s of pages of figures as “supplemental material” Ten years to really understand the details for set of 3 flames Other RANS approaches still trying to get extinction right Only one LES/FDF of flame E (w/ extinction) by V. Raman

12 TNF8 (2006) Target Flames and Phenomena
Bluff-Body Stabilized Sydney University, Sandia High velocity coflow, central fuel jet Flow recirculation CH4/H2, CH4/air, CO/H2 Swirl/Bluff-Body Sydney Univ., Sandia Large-scale instability Vortex breakdown CH4, CH4/air, CH4/H2 Comparisons of measured and modeled results on the Sydney Bluff-Body and Swirl flames coordinated by Andreas Kempf at the TNF8 Workshop

13 TNF8 Workshop (2006) – Comparison Table for BB and Swirl
Prepared by Andreas Kempf

14 TNF Workshop – Successes
improved quality and availability of experimental data for “simple” flames higher “standards” for combustion model validation better understanding of model capabilities and experimental uncertainty a few very productive collaborations collaboration & rapid feedback  accelerated progress for same $$ impact (journal references, use by industry), high visibility 11/20 nonpremixed modeling papers in PCI used TNF data

15 TNF Workshop – Failures
still very few “appropriate, complete” data sets comparisons limited to easiest quantities (point statistics) little information from calculations has been preserved funding for collaborative experimental work in the US is very limited currently no model for growth of TNF Workshop beyond “cottage industry” (larger data sets, more complete comparisons, …) web content editor is way behind!

16 TNF Workshop – Future Directions and Challenges
Larger experimental data sets beyond single point statistics imaging data (PIV, stereo PIV, 2-D and 3-D imaging data) time domain (high-speed imaging, multi-frame, time series…) more complex flames (fuel and flow geometry) Larger simulation data sets highly-resolved LES of lab-scale flames basis for comparison?? – lots of work to do here feature extraction, vis, etc. Connections to other areas premixed, soot, pressure effects, multi-phase educational possibilities more formal “publication” of results comparison “engine”

17 Turbulent Combustion Laboratory
Instantaneous thermochemical state and local flame structure Combined measurement: T, N2, O2, CH4, CO2, H2O, H2, CO 220-mm spacing, 6-mm segment state of mixing (mixture fraction) progress of reaction rate of mixing (scalar dissipation) local flame orientation 8 laser 5 cameras 7 computers

18 New Data Sets Can Take Years to Fully Analyze
Line-imaged Raman/Rayleigh/CO-LIF and Crossed OH PLIF in the “DLR-A” and “DLR-B” flames CH4/H2/N2 (22.1%, 33.2% 44.7%) Nearly constant Rayleigh cross section 8 mm jet exit diameter, 0.3 m/s coflow, ~60 cm flame length DLR-A: Re = 15, DLR-B: Re = 22,800 High resolution Rayleigh (40 mm sample spacing, 50 mm optical) Conditional Mean c DLR-B, x/d=10

19 More Piloted Jet Flames
Piloted CH4/H2/air jet flames Collaboration with Henri Ozarovsky and Peter Lindstedt (Imperial College) High Reynolds number (60,000 and 67,000); f = 3.2, 2.5, 2.1; total of 18 cases Increase local extinction in multiple steps Lindstedt, Ozarovsky, Barlow, Karpetis, Proc. Comb. Inst. 31 (2007)

20 Simultaneous Planar Imaging: Scalar Dissipation
Temperature, T Mixture fraction, x Forward reaction rate, [CO] + [OH]  [CO2] + [H] Scalar dissipation, c J.H. Frank, S.A. Kaiser, M.B. Long, Combust. Flame 143 (2005)

21 High-Speed Multi-Frame OH PLIF Imaging + Stereo PIV
CH4/H2/N2 DLR-B Six Frames of OH PLIF, Dt = 30 ms Strain Rate OH outline J. Hult, U. Meier, W. Meier, A. Harvey, C.F. Kaminski, Proc. Combust. Inst. 30 (2005)

22 Coupling Experiments and Simulations
Direct comparisons with matched bc’s High-fidelity (expensive) Combined experimental & computational benchmarks Turbulent Flame Experiments Address key flame phenomena, but provide only partial information TNF Workshop flames Large Eddy Simulation (LES) Resolve energetic scales, but model subgrid scales

23 Photograph of Experimental Flame
CH4/H2/N2 Flames Nozzle: dINNER= 8.0 mm, tapered to sharp edge Fuel: 22.1% CH4, 33.2% H2, 44.7% N2 Coflow: 99.2% Air, 0.8% H2O Stoichiometric mixture fraction: Zst = 0.167 DLR A: UJET= 42.2 m/s TJET = 292 K Red = 15200 UCOFLOW= 0.3 m/s TCOFLOW = 292 K Flame Luminosity (800 s) Photograph of Experimental Flame

24 Cross-section of 6-million cell 3D curvilinear grid (80cm x 40cm)
State of the art (high-quality) grids Distributed multiblock domain decomposition Adaptive mesh capability (R-refinement technique) CH4/H2/N2 Flames Cross-section of 6-million cell 3D curvilinear grid (80cm x 40cm) 20 Field of view for Kaiser and Frank imaging experiments 10 5

25 Scatter Data (x/d = 10) Experiment LES

26 Data Capacity Requirements for LES and DNS
Unformatted data: Primitives: Q = [ρ, ρu, ρv, ρw, ρet, ρY1, …, ρYN-1]T 8 Bytes/[(Variable)(Grid-Cells)(Time-Step)] 10 variables, 1-million grid-cells  80 Mbytes/Timestep Variables: 10 – 100 (spatial-coordinates + primitives + composite) Grid size (presently): O(1 – 10-million) … LES O(1 – 100-million) … DNS Typical animation uses approximately 200 frames Tradeoff between amount of data stored and cost of post-processing on-the-fly Capacity requirements on the order of terabytes rapidly approached from J. Oefelein

27 LES-FDF Simulation of Sandia Flames
Simulation details 256 x 128 x 32 points 30-50 particles/cell More than 5K time steps Data stored 75 Mb of LES data/timestep 3.75 Gb of FDF data/timestep 20 time-stations stored Mining operations Sub-filter FDF conditioned on filtered scalar fields Conditional mixing plots Flame D Flame E from V. Raman, UT Austin

28 LBNL Laboratory-scale DNS O(10 cm)3
Lean premixed turbulent flames (V- and slot-flames, and low-swirl burners) Very large scale simulations, current datasets O(1-10+) TB Complex detailed chemical mechanisms w/detailed transport, 100’s of reactions Map simulations onto theory / experiment. Use simulations to analyze flames beyond traditional theory/experimental approaches Time-scale of research: Code/algorithm development O(10 yrs) Highly specialized enabling algorithms, ongoing development Data production O(6 mos) Remote supercomputers, high-speed networking, parallel filesystems Validation O(6 mos) Significant interaction with experi- mentalists/theorists Extraction of “new science” O(1 yr) Analysis framework requires multi-year interactions to relate simulations to experimental diagnostics, theory and beyond Requirements for data analysis - Computing resource intensive, supercomputer CPU/disks/archiving - Complex, specialized data structures specific to the simulation - Data manipulation consistent with simulation (physics databases, discretization) - Manpower intensive (specialized analysis driven by multi-disciplinary interactions) - Coordinate efforts amongst math/computer science, theory, experimental diagnostics

29 What might Cyber Infrastructure do for TNF Workshop
Collection, packaging, and distribution of large data sets: Experiments and high-fidelity simulation Reduce labor by standardizing(?) and automating the upload process Allow for archiving of model results in digital form Include functionality to interactively view (plot) data in various ways Promote formation of more collaborative groups Pay for people to build/maintain custom tools for data archiving/analysis Infrastructure is not (currently) the bottle neck for progress in TNF Interagency collaboration to promote research on targeted problems could be very useful

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