turbulent mixing for a jet in crossflow and plans for turbulent combustion simulations james glimm

Turbulent mixing for a jet in Turbulent mixing for a jet in crossflow and planscrossflow and plans

for turbulent combustion for turbulent combustion simulationssimulations

James Glimm

The Team/CollaboratorsThe Team/Collaborators Stony Brook UniversityStony Brook University

James GlimmJames Glimm Xiaolin LiXiaolin Li Xiangmin JiaoXiangmin Jiao Yan YuYan Yu Ryan KaufmanRyan Kaufman Ying XuYing Xu Vinay MahadeoVinay Mahadeo Hao ZhangHao Zhang Hyunkyung LimHyunkyung Lim

Drew UniversityDrew University Srabasti DuttaSrabasti Dutta

Los Alamos National Los Alamos National LaboratoryLaboratory

David H. SharpDavid H. Sharp John GroveJohn Grove Bradley PlohrBradley Plohr Wurigen BoWurigen Bo Baolian ChengBaolian Cheng

Outline of PresentationOutline of Presentation

Problem specification and dimensional analysisProblem specification and dimensional analysis Experimental configurationExperimental configuration HyShot II configurationHyShot II configuration

Plans for combustion simulationsPlans for combustion simulations Fine scale simulations for V&V purposesFine scale simulations for V&V purposes HyShot II simulation plansHyShot II simulation plans

Preliminary simulation results for mixingPreliminary simulation results for mixing Comments on the nature of LES convergenceComments on the nature of LES convergence

Main ObjectiveMain Objective Compare to the Stanford code development effort.

Chemistry to be computed without a model (beyond dynamic turbulence model). Hereby we can offer a UQ assessment of the accuracy of the Stanford code.

If the comparison is satisfactory and the two codes agree, the UQ analysis of the Stanford code (in this aspect) will be complete.

If the comparison is unsatisfactory, we will attempt to determine which of the differing results are to be believed.

Problem Specification andProblem Specification andDimensional AnalysisDimensional Analysis

Experimental configurationExperimental configuration Problem dimensions = 8.6 x 2 x 2 cmProblem dimensions = 8.6 x 2 x 2 cm Parameters for crossflow (air)Parameters for crossflow (air)

• Crossflow Ma = 2.4; flow velocity = 1800 m/sCrossflow Ma = 2.4; flow velocity = 1800 m/s• Crossflow pressure = 0.4 BarCrossflow pressure = 0.4 Bar• Crossflow Temperature = 1548KCrossflow Temperature = 1548K• L (air) = distance of nozzle downstream = 0.067 mL (air) = distance of nozzle downstream = 0.067 m• Viscosity (air) = 5.36e-4 mViscosity (air) = 5.36e-4 m22/s/s• Re (air) = 2.25e5Re (air) = 2.25e5• Kolmogorov scale (air) = L ReKolmogorov scale (air) = L Re-3/4-3/4 = 6.5 microns = 6.5 microns

Parameters for HParameters for H22

• HH22 flow M = 1; H flow M = 1; H22 velocity = 1205 m/s velocity = 1205 m/s• HH22 pressure = 20.2 Bar pressure = 20.2 Bar• HH22 Temperature = 300 K Temperature = 300 K• Viscosity of HViscosity of H22 = 0.16e-4 m = 0.16e-4 m22/s/s• L (HL (H22) = nozzle diameter = 2 mm) = nozzle diameter = 2 mm• Re (HRe (H22) = 1.5e5) = 1.5e5• Kolmogorov scale (HKolmogorov scale (H22) = LRe) = LRe-3/4-3/4 = 11 microns = 11 microns

Flame width (OH, from experiment) = 200 micronsFlame width (OH, from experiment) = 200 microns Momentum flux ratio J = jet/crossflow = 5 Momentum flux ratio J = jet/crossflow = 5


HyShot II Scramjet configuration *HyShot II Scramjet configuration * Combustion chamber dimensions = 29.5 x 0.98 x 7.5 cmCombustion chamber dimensions = 29.5 x 0.98 x 7.5 cm

• Reduced by symmetry to 29.5 x 0.98 x 0.9375 cmReduced by symmetry to 29.5 x 0.98 x 0.9375 cm• Volume is 0.79 as a fraction of the experimental combustion chamber (after symmetry reduction)Volume is 0.79 as a fraction of the experimental combustion chamber (after symmetry reduction)

Crossflow (air) parameters Crossflow (air) parameters • Crossflow Ma = 2.4; flow velocity = 1720 m/sCrossflow Ma = 2.4; flow velocity = 1720 m/s• Crossflow pressure = 130 KPaCrossflow pressure = 130 KPa• Crossflow Temperature = 1300 KCrossflow Temperature = 1300 K• Viscosity of air = 0.000182 m/sViscosity of air = 0.000182 m/s• L (air) = 5 cm (from inflow plane to injector)L (air) = 5 cm (from inflow plane to injector)• Re (air) = 4.7e5Re (air) = 4.7e5• Kolmogorov scale (air) = LReKolmogorov scale (air) = LRe-3/4-3/4 = 2.8 microns = 2.8 microns

HH22 parameters (at injector exit) parameters (at injector exit)• HH22 flow M = 1; velocity = 1200 m/s flow M = 1; velocity = 1200 m/s• HH22 pressure = 4.6 bar pressure = 4.6 bar• HH22 Temperature = 300 K Temperature = 300 K• Viscosity of HViscosity of H22 = 2.22e-5 m = 2.22e-5 m22/s/s• L (HL (H22) = nozzle diameter = 2 mm) = nozzle diameter = 2 mm• Re (HRe (H22) = 1.1 e5) = 1.1 e5• Kolmogorov scale (HKolmogorov scale (H22) = LRe) = LRe-3/4-3/4 = 35 microns = 35 microns

Flame width (OH, from experiment) = 200 micronsFlame width (OH, from experiment) = 200 microns J = ratio of momentum flux jet/crossflow = 0.55J = ratio of momentum flux jet/crossflow = 0.55

*Sebastian Karl, Klaus Hannemann, Andreas Mack, Johan Steelant, “CFD Analysis of the HyShot II Scramjet Experiments in the HEG Shock Tunnel”, 15*Sebastian Karl, Klaus Hannemann, Andreas Mack, Johan Steelant, “CFD Analysis of the HyShot II Scramjet Experiments in the HEG Shock Tunnel”, 15 thth AIAA International Space Planes and Hypersonic Systems and AIAA International Space Planes and Hypersonic Systems and Technologies ConferenceTechnologies Conference


Simulation Parameters: Experimental ConfigurationSimulation Parameters: Experimental Configuration Fine grid: approximately 60 micron gridFine grid: approximately 60 micron grid

• Mesh = 1500 x 350 x 350 = 183 M cellsMesh = 1500 x 350 x 350 = 183 M cells If necessary, we can simulate only a fraction of the experimental If necessary, we can simulate only a fraction of the experimental

domaindomain If necessary, a few levels of AMR can be usedIf necessary, a few levels of AMR can be used Current simulations = 120 microns, about 10 M cells Current simulations = 120 microns, about 10 M cells

HyShot II configurationHyShot II configuration Resolution problem is similarResolution problem is similar

• 3/4 volume after symmetry reduction compared to experiment3/4 volume after symmetry reduction compared to experiment Full (symmetry reduced) domain needed to model unstartFull (symmetry reduced) domain needed to model unstart Resolved chemistry might be feasibleResolved chemistry might be feasible Wall heating an important issueWall heating an important issue

Flow and Chemistry RegimeFlow and Chemistry Regime Turbulence scale << chemistry scaleTurbulence scale << chemistry scale

Broken reaction zoneBroken reaction zone Autoignition flow regimeAutoignition flow regime

TTcc << T << T Makes flame stable against extinction from turbulent fluctuations Makes flame stable against extinction from turbulent fluctuations

within flame structurewithin flame structure Unusual regime for turbulent combustionUnusual regime for turbulent combustion

Broken reaction zone autoignition distributed flame regimeBroken reaction zone autoignition distributed flame regime Query to Stanford team: literature on this flow regime?Query to Stanford team: literature on this flow regime?

• Knudsen and Pitsch Comb and Flame 2009Knudsen and Pitsch Comb and Flame 2009• Modification to FlameMaster for this regime?Modification to FlameMaster for this regime?

Opportunity to develop validated combustion models for this Opportunity to develop validated combustion models for this regime, for use in other applicationsregime, for use in other applications

• Some applications of DOE interestSome applications of DOE interest

Flow, Simulation and Chemistry Flow, Simulation and Chemistry Scales; Experimental RegimeScales; Experimental Regime

Turbulence scale << grid scale << chemistry scaleTurbulence scale << grid scale << chemistry scale• Turbulence scale = 10 micronsTurbulence scale = 10 microns• << grid scale = 60 microns << grid scale = 60 microns • << chemistry scale 200 microns<< chemistry scale 200 microns

Resolved chemistry, but not resolved turbulenceResolved chemistry, but not resolved turbulence Need for dynamic SGS models for turbulenceNeed for dynamic SGS models for turbulence Transport in chemistry simulations must depend on Transport in chemistry simulations must depend on

turbulent + laminar fluid transport, not on laminar turbulent + laminar fluid transport, not on laminar transport alonetransport alone

Chemistry Simulation PlansChemistry Simulation Plans Resolved Chemistry vs. FlameletsResolved Chemistry vs. Flamelets

Flamelets Flamelets • assumes diffusion flame, assumes diffusion flame,

Resolved chemistry Resolved chemistry • makes no assumption of flame structuremakes no assumption of flame structure• thus resolved chemistry is more suitable for an autoignition flamethus resolved chemistry is more suitable for an autoignition flame• FlameMaster has been or will be extended to support autoignition flame structure?FlameMaster has been or will be extended to support autoignition flame structure?

Flamelets Flamelets • use FlameMaster, use FlameMaster,

Resolved chemistry Resolved chemistry • uses FlameMaster subroutine for chemical source termsuses FlameMaster subroutine for chemical source terms

FlameletsFlamelets• assumes a quasi equilibrium solution, thus suppresses certain transients. assumes a quasi equilibrium solution, thus suppresses certain transients. • (This can be either/both a strength or a weakness.)(This can be either/both a strength or a weakness.)• speed and/or memory advantagesspeed and/or memory advantages• Flamelets feasible for coarser gridsFlamelets feasible for coarser grids

Resolved chemistryResolved chemistry• allows UQ assessment of flamelet model in Scramjet context.allows UQ assessment of flamelet model in Scramjet context.• Has value for Scramjet UQ analysis even if too slow to be feasible for most simulationsHas value for Scramjet UQ analysis even if too slow to be feasible for most simulations• May not be feasible for HyShot II configurationMay not be feasible for HyShot II configuration

Simulation Plans:Simulation Plans: Experimental Regime Experimental Regime

Mixed fluid physicsMixed fluid physics Accurate multifluid viscosity, diffusion parametersAccurate multifluid viscosity, diffusion parameters

• Diffusion velocityDiffusion velocity Numerical issuesNumerical issues

Finer resolution gridsFiner resolution grids No need to track frontsNo need to track fronts AMR needed?AMR needed?

Turbulent inflow needed (nozzle/cross flow)?Turbulent inflow needed (nozzle/cross flow)? V&V for pure mixingV&V for pure mixing Add chemistryAdd chemistry V&V for resolved chemistryV&V for resolved chemistry Comparison to flamelet simulationsComparison to flamelet simulations V&V for flameletsV&V for flamelets

Simulation Plans:Simulation Plans:HyShot II RegimeHyShot II Regime

Work with autoignition version of FlameMasterWork with autoignition version of FlameMaster Add this capability if necessaryAdd this capability if necessary

Compare to laboratory experimental regime and resolved Compare to laboratory experimental regime and resolved chemistry simulations (V&V)chemistry simulations (V&V)

Simulate in representative flow regimes defined by the Simulate in representative flow regimes defined by the large scale MC reduced order model, both for failure large scale MC reduced order model, both for failure conditions (unstart) and for successful conditions.conditions (unstart) and for successful conditions.

Provide improved combustion modeling to the MC low Provide improved combustion modeling to the MC low order model, for the next iteration of an MC full system order model, for the next iteration of an MC full system search.search.

Investigate “gates” which serve to couple system Investigate “gates” which serve to couple system components into full systemcomponents into full system

For combustion chamber, primarily fuel nozzle, inlet flow and exit For combustion chamber, primarily fuel nozzle, inlet flow and exit nozzlenozzle

Essential step for relating UQ of components to UQ of full systemEssential step for relating UQ of components to UQ of full system

Preliminary Simulation Results:Preliminary Simulation Results:Mixing OnlyMixing Only

3D simulation. 67% H2 mass concentrationisosurface plot compared to experimental OH-PLIF image (courtesy of Mirko Gamba). The grid is 120 microns, 2 times coarser than the Intended fine grid mesh size.


Black dots are the flame frontextracted from the experimentalOH-PLIF image.


Velocity divergence plotted at the midline plane. Bow shock, boundary layer separation, barrel shock and Mach disk are visible from the plot.


HH22 mass fraction contour plotted at the midline plane


Stream-wise velocityStream-wise velocity contour plotted at the midline plane


HH22 mass fraction contour plotted at x/d=2.4


Stream-wise velocityStream-wise velocity contour plotted x/d=2.4


Mixture fraction plot courtesy of Mixture fraction plot courtesy of Catherine GorleCatherine Gorle0 represents Hydrogen,1 represents Air0 represents Hydrogen,1 represents Air

Mass fraction plot of our simulationMass fraction plot of our simulation1 represents Hydrogen, 0 represents Air1 represents Hydrogen, 0 represents Air


Comparison between Smagorinsky model (left) and dynamic model (right)Comparison between Smagorinsky model (left) and dynamic model (right) Mass fraction plot, using 240 micron gridMass fraction plot, using 240 micron grid


Comparison between 240 micron grid and 120 micron gridComparison between 240 micron grid and 120 micron gridWith dynamic model, mass fraction plotWith dynamic model, mass fraction plot

The Nature of LES Convergence

A mathematical theorem (G-Q Chen and JG) If one assumes K41 as a property of LES

solutions of NS (this is incompressible, but with possible passive scalars) then after to passing to subsequences

• Velocity field converges in some Lq space• Passive scalars (are proved to) converge only as

Young measures, ie measure valued distributions

Young Measures and PDFs Assume this applies to compressible NS as well Implication is that the LES regime defines a convergent

PDF, not a convergent point valued function, even as a weak solution.

If point values are extracted, these are the means of the pdfs

For application to nonlinear processes (chemistry), mean values of pds are not good enough, and fluctuations are needed.

Thus pdf (Young measure) convergence is an important conceptual issue for LES applied to combustion

Young Measure Convergence

How would one define or notice the effects of pdf convergence?

We take a unit size filter (implicit filter). But the values at a point are not meaningful. Rather the ensemble of solution values in an extended neighborhood of the unit filter define an ensemble, which is the pdf for the point or for all points in the extended neighborhood

At the larger filter level size, the limit looks like an ensemble, a pdf, not a point value.

Queries for StanfordQueries for Stanford What is the status/need for autoignition in FlameMaster?What is the status/need for autoignition in FlameMaster? In the broken flame regime, with turbulence inside the In the broken flame regime, with turbulence inside the

flame, flame, what is used for the binary diffusion coefficients that drive the what is used for the binary diffusion coefficients that drive the

effective diffusivity of species k into the mixture? Laminar, from effective diffusivity of species k into the mixture? Laminar, from kinetic theory, or turbulent, from an SGS model? kinetic theory, or turbulent, from an SGS model?

Or are the SGS diffusion terms just a Fickean add on to the Or are the SGS diffusion terms just a Fickean add on to the multicomponent diffusion? multicomponent diffusion?

In this case they should be dominant for most grids, and so the In this case they should be dominant for most grids, and so the multicomponent theory of diffusion might not be needed?multicomponent theory of diffusion might not be needed?

References for the broken flame-autoignition regime?References for the broken flame-autoignition regime?

turbulent mixing for a jet in crossflow and plans for turbulent combustion simulations james glimm

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