Stephen B. Pope
Haifeng Wang, Andrew Garmory, Parvez Sukheswalla
Sibley School of Mechanical & Aerospace EngineeringCornell University
CEFRC Review MeetingPrinceton, NJ
September 23-24, 2010
Processes:Chemical kineticsMolecular transportFlowTurbulence
Systems:Homogenous
systemLaminar flameSimple turbulent
flame (DNS)Device scale
turbulent combustion
Flow, turbulenceLarge-eddy simulation (LES)
Turbulence-chemistry interactionsProbability density function
methods (PDF) Particle/mesh method
ChemistryDetailed or reduced mechanisms
(~50 species)Computationally-efficient
implementation In situ adaptive tabulation (ISAT)
Flame D Flame E Flame FSymbols: expt., Barlow & Frank (1998)Solid lines: PDF with GRI 3.0, Cao & Pope (2005)
Demonstration of capability of PDF methodsto treat turbulence-chemistry interactions:burning index in Barlow & Frank flames
Continued development and improvement of the LES/PDF/ISAT methodology
Studies of existing flames (e.g., TNF)
Studies of existing and future DNS (Chen, Sandia)
Studies of future CEFRC experiments (e.g., spherical premixed flames; Law, Princeton)
Use of reduced mechanisms relevant to transportation fuels
More chemistry!
Incorporating realistic chemistry (e.g., 50 species) is demanding and dominates computational work
Minimize computational work for acceptable accuracy
Improved accuracy in LES and PDF…
Fewer LES cells (for the same accuracy)
Fewer PDF particles per cell (for the same accuracy)
…reduces the number of chemistry calculations required (fewer particles and time steps)
At fixed computational expense, enables the use of mechanisms with more species
Lu & Law
Initial calculations with new HPDF codeStanford LES codeSimple combustion
models
Demonstrate accuracy and consistency of the method
Grid convergence:
Mean profiles:
modified Curl’s model ARM1 chemistry 256x128x32 grid 40 particles/cell ISAT algorithm
Resolved CO2 field
Particle CO2
Scatter plots of CO-CO2-OH (color-coded by ξ)
Scatter plots of particle CO2 against radial distance r/D (colored coded by ξ)
Scatter plots of particle CO2 against mixture fraction ξ (colored coded by r/D)
LES of a constant density free jet (Amielh et al., 1996)
Grid: 288x192x144 in x, r, θ directions (8M cells)
Radial profiles of resolved turbulence intensity and shear stress in the near field (x/D=0.2)
(Wang, Pope & Caughey, 2010)
SCHEME-ISCHEME-IIExp. Data
SCHEME-I
96x64x48(0.3M cells)
144x96x72(1M cells)
Exp. Data
SCHEME-II
96x64x48(0.3M cells)
144x96x72(1M cells)
Exp. Data
Grid Ratio of cells Ratio of work
1 1 1
2 3.3 5
3 27 80
(Wang, Pope & Caughey, 2010)
Non-uniform grids stretched in the flow direction (symbols indicate the grid points)
(Wang, Pope & Caughey, 2010)
Development of LES/PDF/ISAT methodology:LES – flow and turbulencePDF – turbulence-chemistry interactions ISAT – computationally efficient
implementation of realistic combustion chemistry
Initial studies:DLR-ASandia flame D
Improved numerical methods allow a fuller treatment of chemistry
Future:Comparison with DNS (Chen, Sandia)Premixed spherical flames (Law,
Princeton)Use of CEFRC mechanisms (< 600 species)