Development of a Detailed Surface Chemistry Framework in SPARTA

K. Swaminathan-Gopalan,a A. Borner,b K. A. Stephaniaa Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign,

b Science and Technology Corporation at NASA Ames Research Center

Acknowledgments

This work was performed under the Entry System Modeling Project (M. J. Wright, Project Manager) for the NASA Game Changing Development (GCD) Program and supported by NASA Grant NNX15AU92A.

DSMC Workshop 2017 Santa Fe, NM27th – 30th Aug 2017

https://ntrs.nasa.gov/search.jsp?R=20180000108 2020-07-01T04:28:25+00:00Z

Outline

§ Motivation

§ Overview of Surface Chemistry Framework

§ Gas-Surface (GS) Reactions

§ Pure-Surface (PS) Reactions

§ Applications

§ Parallelization strategies

§ Summary and Future Work

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Motivation

Objective:To construct a general, detailed physics-based surface chemistry framework in DSMC.

Ablative TPS

3

Adsorption and reactive surface chemistry

Somorjai andLi[1]

Imagecredit:NASA

1 Somorjai, G. A., & Li, Y. (2010). Introduction to surface chemistry and catalysis. John Wiley & Sons.

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Surface chemistry at microporous catalysts.

Flow through porous preform carbon TPS using SPARTA. Imagecredit:Sandstorm

Computational framework

• Finite-ratesurfacechemistrymodulewithadsorption.• Includesgas-surface(GS)andpure-surface(PS)reactions.• Bothcatalyticandsurfacealtering(oxidation/nitridation)reactions.• ComputationalframeworksimilartoMarschall,MacleanandDriver[2,3]forCFD.• Langmuirmodelforsurfacesites.• DiverseVDFandangulardistributionsofscatteredproducts.

takenfromMarschall andMaclean[1].

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3 Marschall, J., & MacLean, M. (2011). Finite-rate surface chemistry model, I: Formulation and reaction system examples. AIAA Paper, 3783, 2011.3 MacLean, M., Marschall, J., & Driver, D. M. (2011). Finite-rate surface chemistry model, II: coupling to viscous Navier–Stokes code. AIAA Paper, 3784, 2011.

Computational framework

• Particlesadsorbed(deleted)anddesorbed(created),surfaceelementstoresadsorbedparticleconcentration.

• Surfacereactionsbasedonconcentrationwithinsurfaceelement.• Multipletriangulatedelements(likecells)onsurfaces• Surfacetreatedasinfinitesinkandsource.

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takenfromMarschall andMaclean[1].

3 Marschall, J., & MacLean, M. (2011). Finite-rate surface chemistry model, I: Formulation and reaction system examples. AIAA Paper, 3783, 2011.3 MacLean, M., Marschall, J., & Driver, D. M. (2011). Finite-rate surface chemistry model, II: coupling to viscous Navier–Stokes code. AIAA Paper, 3784, 2011.

List of gas-surface (GS) reactions

• Reactantsincludebothgas-phaseandsurfacespecies.• Comprehensivesetofreactions– Includesreactiontypesfromthermalregimeand

hyperthermalenergyregime.

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Modeling of gas-surface (GS) reactions

• GSreactionprobabilitycomputedwhengas-phasespecieshitssurface.• Reactionprobabilityfunctionof:

o rateconstanto gas-phaseparticleproperties(energy,angle,etc.)o surfaceconditions(temperature,surfacecoverage,etc.)

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List of pure-surface (PS) reactions

• Pure-surface(PS)reactantsincludeonlysurfacespecies(adsorbedandbulk).• Comprehensivesetofreactions

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Modeling of pure-surface (PS) reactions

• Characteristictimecomputedbetweentworeactions:Timecountermethod[5].• Characteristictimefunctionof

o reactionrateconstanto surfaceconditions(temperature,surfacecoverage,etc.).

• Timecounteralgorithmsdevelopedtobeindependentofdt.

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5 Molchanova, A. N., A. V. Kashkovsky, and Ye A. Bondar. "A detailed DSMC surface chemistry model." In AIP Conference Proceedings, vol. 1628, no. 1, pp. 131-138. AIP, 2014.

Scattering models

CurrentmodelsinSPARTA• Specular• Diffuse– Maxwell’smodel

Additionalmodels• CLLmodel– Thermalregimescattering.Cancapturefullandpartialenergyand

angularaccommodation[6,7].• Thermal– Thermallydesorbingparticleswithoptionssuchasdesorption

barrier,additionalenergytransferduetolocalhot-spots,etc.• Impulsive– Structuralregimescatteringathyperthermalenergies.• Non-thermal– Transitionregimescatteringatsuperthermal energieswithout

fullaccommodation

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6 Lord, R. G. (1991). Some extensions to the Cercignani–Lampis gas–surface scattering kernel. Physics of Fluids A: Fluid Dynamics, 3(4),706-710.7 Lord, R. G. "Some further extensions of the Cercignani–Lampis gas–surface interaction model." Physics of Fluids 7, no. 5 (1995): 1159-1161.

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Application: Simulating Beam Experiments

• PerformDSMCsimulationsofthemolecularbeamexperimentsofoxygenbeamonVitreousCarbonandFiberform – Murrayetal [8].

• Usedtoconstructafiniteratesurfaceoxidationmodelforcarbon.

8 Murray, V J., et al. "Inelastic and Reactive Scattering Dynamics of Hyperthermal O and O2 on Hot Vitreous Carbon Surfaces." The Journal of Physical Chemistry C 119.26 (2015): 14780-14796.

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Vitreous carbon

FiberForm®

SPI Supplies

100µm

25mm

Murray et al [1]

O:1875K

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Application: Vitreous Carbon Oxidation Model

DSMC Workshop 201728th Aug 2017

CO:1875K

O:1875K

CO:1875K

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Application: Vitreous Carbon Oxidation Model

Parallelization in DSMC with surface chemistry

• Particleonthesurfaceisnotstoredanymore(onlyitsinformation).

• Parallelizationbasedonthenumberof(gas-phase)particleswillnotworkinDSMC-SC

• TwoadditionalkernelsinDSMC-SC– GSandPSreactions.

• Move• Collide• GS(Gas-Surface)reactions• PS(Pure-Surface)reactions

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DSMC

DSMC-SC

Surfaceboundary

Newpartition

Oldpartition

Flowchart for DSMC-SC

Move

Collide PS

PSGSif(surf)

if(surf)

M+GS

C+PS

15DSMC Workshop 201728th Aug 2017

Twostrategies

1. Keeptrackofthecomputertimetakenforeachcellforalengthoftime.Usethisinformationtopartitionthedomain.• Workswellforsteadyflows

2. Doapproximatecalculationofthecomputertimebasedontheinformationandthealgorithmsused.

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Parallelization in DSMC with surface chemistry

• tmove =O(np *nsteps){moving}+O(np *nsteps){boundary/surface/cellexitcheck}

• tGS =O(nsurf-elem *nsurf-coll *nGS-rxns)

• tcollide =O!.#∗&'(

)*{assumingtemperatureandcrosssectionsareconstant}

• tPS =O(nsurf-elem *nPS-rxns-occur *nPS-rxns)nPS-rxns-occur =+,

-./0(!.#)∑ 𝜈5&67859:

• 𝜈5α Rate(k,nad,order)

tC+PS =tcollide +tPS tM+GS =tmove +tGS

17DSMC Workshop 201728th Aug 2017

Parallelization in DSMC with surface chemistry

Summary• A general, detailed, physics-based surface chemistry framework implemented in

SPARTA.

• Includes physical models with wide range of options and parameters to captureall/several experimental details.

• Capability to model various types of surface reactions accommodating userspecified reaction rates, surface properties and parameters.

Future Work• Further develop and implement parallelization strategies.

• Extension to ionization and plasma chemistry.

• Inclusion of internal energy scattering details.

Summary and Future Work

18DSMC Workshop 201728th Aug 2017

• This work was performed under the Entry System Modeling Project (M. J.Wright Project Manager) at the NASA Game Changing Development (GCD)Program and supported by NASA Grant NNX15AU92A.

Acknowledgements

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Backup Slides

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Adsorption modeling

• Adsorption:directandindirectpathways.• DirectadsorptioncapturedusingtheLangmuirmodel.• Kisliuk model[4]usedtocapturetheindirectadsorptionpathway.• Keq isanadditionalparameter– Keq=0givestheLangmuirmodel.

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4 Kisliuk, P. "The sticking probabilities of gases chemisorbed on the surfaces of solids." Journal of Physics and Chemistry of Solids 3, no. 1-2 (1957): 95-101.

Eley-Rideal (ER) mechanism : A(s) + B à AB + (s)

Langmuir-Hinshelwood (LH) mechanism : A(s) + B(s) à AB + 2(s)

From: UCL Center for Cosmic Chemistry and Physics

Surface Reaction Mechanisms

2231st Aug 2017 9th Ablation Workshop 2017

The Langmuir-Hinshelwood mechanism has two steps –

Based on time scale arguments 4 types of LH mechanisms can be defined

1. tf << τ td << τ - Prompt thermal mechanism

2. tf ~ τ td << τ - LH limited by formation3. tf << τ td ~ τ - LH limited by desorption4. tf ~ τ td ~ τ - LH limited by both desorption and formation

Timescaleofinterest=τ𝑂 𝑔 + 𝐶 𝑏 → 𝐶𝑂 𝑔 (3)

𝑂 𝑔 + 𝑠 → 𝑂 𝑠

𝐶𝑂 𝑠 → 𝐶𝑂 𝑔 + 𝑠 (2) − 𝑡+

𝑂 𝑠 + 𝐶 𝑏 → 𝐶𝑂 𝑠 1 − 𝑡G

FormationDesorption

Different Types of LH Mechanisms

𝑂 𝑠 – Reactant𝐶𝑂 𝑠 – Intermediate𝐶𝑂 𝑔 – Product

2331st Aug 2017 9th Ablation Workshop 2017