APPLICATION OF RANS/PDF & LES/FDF METHODS TO PREDICTION OF PREMIXED TURBULENT FLAMES

1. APPLICATION OF RANS/PDF & LES/FDF METHODS TO PREDICTION OF PREMIXED TURBULENT FLAMES S.L. Yılmaz Department of Mechanical Engineering and Material Science Ph.D. Proposal December 5th 2007

2. Outline • Objectives summary • PDF/FDF methodologies • Flame configurations • Preliminary Results • Scalable parallelization • Tasks summary

3. Concluding remarks [Drozda 2005] • Sandia Flame D and Sydney/Sandia bluff-body stabilized flames are simulated via the LES/SFMDF • Transport equation for the FDF is solved via the hybrid Eulerian-Lagrangian method. • MKEV and Smagorinsky models are considered for the SGS stresses and fluxes. • Flamelet chemistry model relates the thermo-chemical variables to the mixture fraction. Future/Ongoing work • Prediction of non-equilibrium flames via scalar FMDF and ISAT. • Prediction of turbulent flames via joint velocity-scalar FDF and FMDF. • Optimization of the solver to reduce computational requirements.

4. Objectives • Extend the boundaries of two novel methodologies for prediction of turbulent flames, • Predict a bluff-body burner with a RAS/PDF methodology, • Predict a pilot-stabilized burner with a LES/FDF methodology, • Employ non-equilibrium kinetics, • Develop scalable LES/FDF computational code.

5. DNS, LES, and RAS Reynolds Average Simulation (RAS) Direct Numerical Simulation (DNS) Large Eddy Simulation (LES)

6. Starting Equations

7. Averaging versus Filtering • Statistical description: Turbulent fields are Random Signals in time and space. • RANS: Define one-point, one-time joint-PDF • LES: Define spatial low-pass filter

8. Transported PDF Methods • Solve the one-point one-time Joint PDF directly • Closed quantities • Unclosed quantities

9. PDF Transport Equation • From full-set of NS equations: • Solves for LHS closed, RHS needs model

10. RANS Connection • Ensemble-mean equations derived from JPDF transport equation: • Define Favre averages:

11. Filtered Density Function (FDF) • Formal definition: • Satisfying the properties of PDF

12. Transport of FDF • Identically to PDF transport:

13. Scalar FDF • Transport equation of the marginal FDF of scalars

14. Lagrangian PDF Models • Closure via Stochastic Differential Equations • e.g. The Velocity-Scalar-Frequency SDEs

15. Modeled PDF Transport Equation • Corresponding Fokker-Planck equation

16. Lagrangian FDF Model • SDEs for closure • Fokker-Planck equation

17. Simulation Procedure • Monte-Carlo simulation of the SDEs • Finite Difference solution of Eulerian Filtered or Averaged equations

18. Bluff Body Lean Premixed Flame Pan (1991); Velocity measurements Nandula (2007); Temperature, species concentrations measurements Re = 43,400 Φ = 0.59

19. Simulation Details • Axisymmetric, adiabatic walls, uniform inlet.

20. Comparison of Mean Velocities

21. Mean and RMS Velocities

22. Temperature and Major Species

23. Temperature and Minor Species

24. Premixed Bunsen Burner Y.C. Chen 1996. Velocity, temperature, species measurements. Three Flames of Re = 24K, 40K and 52K Φ = 1.0

25. Cold Flow Computations • Using only FD solver with MKEV turbulence model

26. Parallelization Monte Carlo solver consumes 95% of total time.

27. Load Balancing Problem Stiff Term Region of Low Activity Region of High Activity

28. Load Balancing Problem

29. Uniform Partitions

30. Balanced Partitions! (with METIS)

31. 3D Arbitrary Partitions

32. Task Summary • Modify RAS/PDF computational code for Bluff Body configuration • Perform RAS/PDF simulation of the Bluff Body • Implement detailed kinetics into LES/FDF solver • Implement scalable FDF computational code • Perform LES/FDF simulation of the Bunsen Burner

33. Also thanks to, CTPL members! Cornell Combustion NETL PSC THANK YOU.