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)