NASA Technical Reports Server (NTRS) 20150017057: Assessment of Laminar, Convective Aeroheating Prediction Uncertainties for Mars-Entry Vehicles

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by  NASA Technical Reports Server (NTRS)

JOURNALOFSPACECRAFTANDROCKETS
Vol.50,No.1,January–February2013
Assessment of Laminar, Convective Aeroheating Prediction
Uncertainties for Mars-Entry Vehicles
BrianR.Hollis∗
NASALangleyResearchCenter,Hampton,Virginia23681
and
DineshK.Prabhu†
ERCCorporation,MountainView,California94035
DOI:10.2514/1.A32257
An assessment of computational uncertainties is presented for numerical methods used by NASA to predict
1 laminar, convective aeroheating environments for Mars-entry vehicles. A survey was conducted of existing
218 experimentalheattransferandshock-shapedataforhigh-enthalpyreacting-gasCO2flows,andfiverelevanttest
1.6 serieswereselectedforcomparisonwithpredictions.Solutionsweregeneratedattheexperimentaltestconditions
14/ usingNASAstate-of-the-artcomputationaltoolsandcomparedwiththesedata.Thecomparisonswereevaluatedto
5
0.2 establishpredictiveuncertaintiesasafunctionoftotalenthalpyandtoprovideguidanceforfutureexperimental
OI: 1 testingrequirementstohelplowertheseuncertainties.
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aa. Nomenclature suchnewmissions.Thus,anEntry,Descent,andLandingSystems
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EARC RRmNax == mheamxiimspuhmerircaadlinuos,semradius,m asieornodsyynstaemmicardeescheolewrantoinr,Faignsd.2h–y4p.ersonic/supersonic retropropul-
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LE z = Cartesiandistancefromnosealongsymmetryplane,m namic environment, which includes the surface heat transfer,
NG (cid:4) = angleofattack,deg pressure and shear, and the integrated aerodynamic forces and
LA (cid:5) = coneangle,deg momentsthattheentryvehiclewillexperience,mustbedefined.A
ASA (cid:2)1 = freestreamdensity,kg=m3 wstehpichtowwaarsdpefurflofirlmlinegdtahsisparretqoufireamlaerngterisacptrievsiteynt[e2d]isnpotnhsisorsetdudbyy,
N
y NASA’sFundamentalAeronauticsProgram,HypersonicsProjectto
b
ed I. Introduction define,andultimatelyreduce,aerothermodynamicuncertaintiesfor
d
oa TWO important goals for NASA’s future Mars exploration severalhypersonicmissiontypes.Avarietyofphysicalphenomena
wnl programsaretoperformaroboticsamplereturnmissionand thatinfluencetheHMMES aerothermodynamic environmenthave
Do toenablehumanexplorationmissions.Bothgoalsrequirethesafe beenidentified.Theseinclude,butarenotlimitedtothefollowing:
landing of much greater masses (in excess of 10 t) than those boundary-layer transition; TPS blowing, ablation, and roughness;
of previous Mars missions. However, the heritage technology shock-layer radiation; flexible structure/flowfield interactions;
employed in past NASA missions from Viking to Mars Science retropropulsion thruster and reaction control system jet/flowfield
Laboratory (MSL), that of a rigid, 70 deg sphere-cone, ablative and jet/surface interactions; noncontinuum effects at high altitude
thermalprotectionsystem(TPS),willnotbesufficienttoaccomplish andinseparatedwakeflows;surfacecatalysis;nonequilibriumgas
kinetics, etc. A discussion of many of these phenomena and of
computationalmethodsusedformodelingthemispresentedin[3].
Presented as Paper 2011-3144 at the 43rd AIAA Thermophysics
Conference, Honolulu, HI, June 27–30, 2011; received 19 October 2011; Thesensitivitiesofthesecomputationalmethodstoinputparameters
revisionreceived27April2012;acceptedforpublication13May2012.This for numerical models of physical phenomena (as distinct from
material is declared a work of the U.S. Government and is not subject to uncertainties determined through comparison with experimental
copyrightprotectionintheUnitedStates.Copiesofthispapermaybemadefor data,whichisthesubjectofthisreport)havebeenexploredin[4].
personalorinternaluse,onconditionthatthecopierpaythe$10.00per-copy The current study is limited to uncertainties in the prediction
feetotheCopyrightClearanceCenter,Inc.,222RosewoodDrive,Danvers, of laminar, attached high-enthalpy flow of CO over smooth,
MA01923;includethecode0022-4650/13and$10.00incorrespondencewith nonablating surfaces. These restrictions define 2the most basic
the∗CACerCo.space Engineer, Aerothermodynamics Branch. Associate Fellow validationcase(shortofperfect-gasflow)relevanttoMarsmissions.
Withoutathoroughunderstandingofthecomputationaluncertainties
AIAA.
†Senior Research Scientist, Aerothermodynamics Branch; currently inthemodelingofthesephenomena,uncertaintiesinmodelingother
NASAAmesResearchCenter,MoffettField,California94035.Associate phenomena, such as turbulence, roughness, and radiation, cannot
FellowAIAA. properlybeaddressed.
56
HOLLISANDPRABHU 57
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3 | Fig.1 HMMESarchitectureoptions.
1
0
2
5,
1
h
arc The approach followed to define the uncertainties for laminar,
M
on attachedhigh-enthalpyCO2flowswasasfollows:
E 1) Identify relevant sources of experimental data (i.e., high-
TR enthalpysurfaceandflowfieldtestdataobtainedinCO flows).For
N 2
E simplicity,only0degangle-of-attackdatawereconsidered.
C
H 2) Generate flowfield predictions at the selected test conditions
C
R usingthestate-of-the-artcomputationaltoolscurrentlyemployedin
A
E thedevelopmentofNASA’sMarsmissions.Althoughcomputations
S
RE may have been previously performed for some data sets using
Y older software packages, itisimportant to emphasize that, for the
E
GL purposesofthecurrentstudy,newsolutionsweregeneratedforall
AN cases.Thenewsolutionsweregeneratedtoensurethataconsistent
A L methodology was applied using the latest software versions.
AS Similarly, although other similar software tools exist outside of
y N NASAandhavebeenemployedtomodelsuchflows,theywerenot
d b consideredinthisstudy.
e
d 3)Performandassesscomparisonsbetweentheexperimentaldata
a
nlo Fig.2 Mid-L=Drigidaeroshell. and numerical results to determine the current state of the art in
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o
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Fig.3 Inflatableaerodynamicdecelerator. Fig.4 Supersonicretropropulsionsystem.
58 HOLLISANDPRABHU
datathatdidnotmeetthecurrentcriteriawerealsonotedforfuture
consideration(e.g.,turbulentdata,high-enthalpyairorN data).
2
A. ExperimentalDataSetsforHMMESLaminar,Convective
UncertaintyAssessment
Five sources of laminar high-enthalpy, convective heat transfer
data in a CO environment were identified for inclusion in this
2
study. These data were obtained in the NASA Ames Research
Center(ARC)42-InchShockTunnel,theGeneralAppliedSciences
Laboratories(GASL)HYPULSEExpansionTube,theCaltechT5
Reflected Shock Tunnel, the University of Illinois Hypervelocity
Expansion Tube, and the Calspan University of Buffalo Research
Center(CUBRC)LENSIReflectedShockTunnel.Alldataarefrom
70degsphere-conemodelgeometries(Fig.5)similartothatofMSL,
althoughthereissomevariationinnoseandcornerradiusdimensions
(relativetothemaximumradius)ofthemodelstested.
Test conditions from each of these studies are listed in
81 chronological order in Table 1 and a summary of thewind-tunnel
1
62 modelparametersforeachtestisprovidedinTable2.Notethatthe
1.
4/ conditionslisteddonotnecessarilyrepresentallthedataobtainedin
1
25 eachfacility;forsimplicity,thedataconsideredhereinwerelimited
10. to0degangleofattackatlaminarconditions.Additionaldatafor
OI: Fig.5 Seventydegreesphere-conegeometry. nonzeroangleofattackandfortransitionalandturbulentboundary
D
g | layersarealsoavailableinmanyofthesedatasets.Itisalsoimportant
or to note that these test conditions were actually determined from a
aa. computational predictions for laminar high-enthalpy, convective combination of experimental flowfield measurements (e.g., shock
c.ai aerothermodynamicenvironmentsofMarsmissions. speedandpitotpressure)andnumericalsimulationtools(toobtain
http://ar artItwisilelxpbeectuesdedthaatsthgeuriedseullitnseosftfhoirsefufftourrtetoedffeofirtnsetthoersetdatuecoeftthhee mphaysssicfaralcmtioodnesl)s.aTshdeosethneuflmoewrificealldtcooodlsesewmhpilcohyasroem,ientohfeothrye,stoambee
3 | computationaluncertainties.Reductionofthemodelinguncertain- validated by comparison with the experimental data. Thus, a
201 ties will require the acquisition of new high-fidelity experimental completevalidationexercise,whichisoutsidethescopeofthisstudy,
ch 15, gnraomuincds-praonpderfltiiegsh(ts-tuersftacdeathaeaotningboatnhdmpraecsrsousrceo,pfliocwafieerlodthsetrrumcotudrye-, wmooudledl-rienq-fluoirweisteimrautilvaetiorenfis.nementsoftestconditionpredictionsand
Mar aerodynamicsforcesandmoments,boundary-layertransition,etc.) Theenthalpy/Reynoldsnumberrangeofthetestdataisshownin
on and fundamental physical properties (chemical, vibrational, and Fig.6.Totalenthalpies(H (cid:5)H )rangedfrom1.9(neartoperfect
RE electronicexcitationandrelaxationrates,transport properties, and gas)to12:3 MJ=kg(noneq0uilibrwiaullmchemistry).Reynoldsnumbers
NT radiation emission and absorption rates). Concurrent development (basedondiameter)foralldataconsideredwerelessthan106,which
H CE awnidllvaalsloidbateiorenqoufiraeddv.ancedcomputationalmethodsandalgorithms resulted in laminar conditions for all cases except one partly
C transitionalrunintheCUBRCdataset.
R
A For comparison with flight conditions, reference values for
E
ES II. ReviewofExperimentalDataApplicable HMMES mid-L=D and HIADS configurations are shown on this
R
Y toHMMESMissions plot,aswellasreferencevaluesfortheMarsScienceLaboratoryand
GLE Athoroughliteraturesearchwasperformedtoidentifysourcesof MarsVikingmissions.ItisnotablethattheMSLreferencecondition
N isatthehighendoftherangeofReynoldsnumberandenthalpytest
A experimentaldatarelevanttotheHMMESuncertaintyassessment.
d by NASA L Dtcirnoaanentxadsfciteseireostsnsmsowefwa1ehsrueMerreeJsm=eplkoeegnsct)tts.sehAdowlcftehkororecuhcgpeohemnrstfihiocdearemlarrcaeettdauiocantilin,oconipnmsuwrpweoehsrCieictOihgoe2nsnuoeterrffasattthceeegdaM(hsi.eaeaar.-tt, chnmoiuginmshsdebiiotreinroi.nniIssne,wncwteohlhnaletlwrrpaeyisatths,aintnthhdetehapeHnerMaoaknrMdgheeeEraoStoiffnctgoemsncatdogcintnoidinotidnutiisdoteinaorgnfeorser.aattfheaercMtionraRrosefVy2nikotoilndg3s
wnloade tthiaenaktimneotsicpsheorfeiCsO(cid:4)295a:r3e%eCxOpe2c,t2e:d7%toNb2,eanthde2.g0r%eatAesrt(buynvcoerlutaminet)y, 1. NASAARC42-InchShockTunnelData
o componentbecauseofitspredominance,andsodatasetswithN (or Data were obtained [5] at laminar test conditions on a 70 deg
D 2
otherminorcomponents)werelefttolaterconsideration.Additional sphere-cone model in CO , air, and CO -Ar environments in the
2 2
Table1 Testconditions
Facility Facilitytype (cid:2)1,kg=m3 T1,K U1,m=s Re1;D H0(cid:5)Hw, Freestreammassfractions
MJ=kg
[CO ] [CO] [O ] [O]
2 2
NASAAmes42-InchShock Reflectedshocktunnel 3:10(cid:6)10(cid:5)4 200 4150 0:25(cid:6)106 8.5 1.000 0.000 0.000 0.000
Tunnel
GASLHYPULSE(runs747,749) Shockexpansiontube 5:79(cid:6)10(cid:5)3 1088 4772 0:93(cid:6)106 12.3 1.000 0.000 0.000 0.000
CaltechT5(run2256) Reflectedshocktunnel 5:70(cid:6)10(cid:5)2 1407 2732 1:67(cid:6)106 6.1 0.831 0.108 0.061 0.000
CaltechT5(run2254) Reflectedshocktunnel 3:12(cid:6)10(cid:5)2 1828 3367 1:25(cid:6)106 10.6 0.550 0.287 0.151 0.012
CaltechT5(run2255) Reflectedshocktunnel 7:83(cid:6)10(cid:5)2 2188 3514 2:26(cid:6)106 11.3 0.592 0.259 0.139 0.009
CUBRCLENSI(series1,run12) Reflectedshocktunnel 5:26(cid:6)10(cid:5)4 691 2761 0:29(cid:6)106 4.9 0.901 0.063 0.036 0.00
CUBRCLENSI(series2,run16) Reflectedshocktunnel 1:48(cid:6)10(cid:5)2 361 1907 0:94(cid:6)106 1.9 1.000 0.000 0.000 0.000
CUBRCLENSI(series2,run12) Reflectedshocktunnel 8:70(cid:6)10(cid:5)3 931 2939 0:77(cid:6)106 6.0 0.843 0.100 0.057 0.000
CUBRCLENSI(series2,run08) Reflectedshocktunnel 8:96(cid:6)10(cid:5)3 892 2870 0:21(cid:6)106 5.6 0.863 0.087 0.05 0.000
CUBRCLENSI(series2,run13) Reflectedshocktunnel 6:06(cid:6)10(cid:5)3 1116 3373 0:16(cid:6)106 8.6 0.687 0.199 0.110 0.003
UniversityofIllinoisHET Shockexpansiontube 1:44(cid:6)10(cid:5)2 1172 3058 0:43(cid:6)106 5.7 1.000 0.000 0.000 0.000
HOLLISANDPRABHU 59
Table2 Wind-tunnelmodelinformation
Facility Max Nose Corner Cone Modelinstrumentation Model Refs.
radius,in. radius,in. radius,in. angle,deg material
NASAAmes42- A(cid:3)2:74 A(cid:3)1:5 A(cid:3)0:039 70 Surfacejunctionthermocouples Copper [5]
InchShock B(cid:3)2:82 B(cid:3)1:5 B(cid:3)0:167
Tunnel C(cid:3)2:99 C(cid:3)1:5 C(cid:3)0:470
GASLHYPULSE 1.00 0.5 MP1(cid:3)0:05 70 Thin-filmtemperaturegauges Macorceramic [6–8]
MP3(cid:3)0:10
MP4(cid:3)0:20
CaltechT5 3.50 1.75 0.35 70 Fast-responsecoaxialthermocouples SS304stainless [9,10]
steel
CUBRCLENSI, 12.0 6.0 0.60 70 Thin-filmtemperaturegaugesandcoaxial Stainlesssteel [11,12]
series1 thermocouples
CUBRCLENSI, 6.0 3.0 0.30 70 Coaxialthermocouples,thin-film Stainlesssteel [13]
series2 temperaturegauges,andsilver
calorimeters
Universityof 1.00 0.5 0.05 70 Fast-responsecoaxialthermocouples AI2024andA2 [14]
IllinoisHET toolsteel
1
8
1
2
6
1.
514/ NASAARC42-InchShockTunnel(alsosometimesreferredtoasthe Tunnel in CO2 and N2 test gases.The modelwas fabricated from
0.2 Ames3.5ftShockTunnel).Thefacility(sincedemolished)wasa stainless steel and instrumented with fast-response coaxial
DOI: 1 Hcoematbtursatniosfne-rhdeaatteada,nrdeflfleocwtefideslhdoscckhtluienrneenliwmitahge1s0–w2e0remosbtteasitnteimdeosn. tahnedrm1o6coduepglesa.nTdesltaimnginwara,stpraenrfsoitrimonedal,ataanndgletusrobfulaetntatckdaotaf0w,1er1e,
g | copper models instrumented with surface thermocouples. Three produced,althoughonlylaminar0degrunsareconsideredherein.
a.or separateconfigurationswereactuallytested.Allwere70degsphere- Althoughaspecificvalueforexperimentaluncertaintywasnotcited
a
ai cone geometries with 1.5 in. nose radii; however, the model had for the CO data of [9], error bars shown on the plots were
arc. interchangeableoutersectionswithvariouscornerradiithatresulted approximate2ly(cid:7)11%.
p:// in2.74–2.99in.maximumradiusmodels.Besidesthe0degangle-
13 | htt o(cid:4)f(cid:3)-att1a0ckanrdun2s0cdoengs.iAdenreedxpheerriemine,natadlduitniocenratlairnutnysowfe(cid:7)re10p%erfworamsceidteadt 4. CUBRCLENSIReflectedShockTunnelData
15, 20 fortheheatingdatafromthisstudy. intMheeaCsUurBeRmCenLtsEoNnSMIRSLeflgeecotemdeStrhyomckoTdeulnsnwele.rTewpeortfeosrtmseerdieisnwCeOre2
ch performed:thefirstwithathermocoupleandthin-filminstrumented,
Mar 2. GASLHYPULSEExpansionTubeData 12in.maximumradiusmodel[11,12]andthesecondwitha6in.
on Testingwasperformed[6–8]intheGASL(nowATK)HYPULSE maximumradiusmodelinstrumentedwiththin-filmgauges,coaxial
E
R ExpansionTubeon70degsphere-conemodelsof1.00in.maximum thermocouples, and silver calorimeters [13]. Both models were
T
N radiusinairandCO testgases.Laminardatawereobtainedonthree fabricated from stainless steel. In addition to the 0 deg angle-of-
E 2
C 70degsphere-conemodelsofvaryingcornerradiiandonablunted attackdataconsideredherein,runswerealsomadeat(cid:4)(cid:3)11,16,and
CH hyperboloid with 70 degasymptotes. The models were fabricated 20 deg that produced laminar, transitional, and turbulent flows.
R
A from Macor ceramic and instrumented with thin-film heat-flux Although specific values for experimental uncertainties for each
E
ES gauges. In addition to the (cid:4)(cid:3)0 data considered herein, data are gaugetypewerenotgiven,errorbarsshownonplotsin[13]were
Y R also available for 4 and 8 deg angles of attack. An experimental approximately(cid:7)5to(cid:7)10%.
LE uncertainty of (cid:7)11% was cited for the heating data from this
NG study. 5. UniversityofIllinoisHypervelocityExpansionTubeData
A
A L Themostrecentdataavailable[14]wereobtainedintheUniversity
AS 3. CaltechT5ReflectedShockTunnelData ofIllinoisHypervelocityExpansionTube(HET).Thetestgeometry
y N Heattransfertestswereperformed[9,10]ona3.50in.maximum wasa1.00in.maximumradius,70degsphere-conestainlesssteel
d b radius,70degsphere-conemodelintheCaltechT5ReflectedShock model instrumented with fast-response coaxial thermocouples.
e
d Laminar data were obtained at angles of attack of 0, 11, and
a
nlo 16 deg. An uncertainty of (cid:7)8% was cited for the coaxial gauge
w
o measurementsbutanoverallexperimentaluncertaintywasnotgiven.
D
B. OtherRelevantSourcesofHigh-EnthalpyConvective
AeroheatingData
Other sources for high-enthalpy aeroheating data sets exist that
may be of use in defining uncertainties in nonequilibrium kinetic
modelseventhoughthesedatawerenotobtainedinpureCO flows.
2
These include, as previously noted, CO -Ar and air data from the
2
ARC42-InchShockTunnel[5],airdatafromGASL-HYPULSE[6–
8],andN datafromCaltechT5[10].
2
Other blunt-cone aeroheating data were obtained in several
facilitiesaspartoftheNATOAGARDWorkingGroup18activity
[15].Althoughtheprimarypurposeofthisprogramwastoobtain
rarefied wake flow data [16], high-enthalpy forebody aeroheating
datawerealsogeneratedintwoofthetests[17]:thoseconductedat
DLR-high enthalpy shock-tunnel Göttingen (DLR-HEG) and
CUBRCLENS.
The DLR-HEG tests was conducted on a 70 deg sphere-cone
modelwithhigh-enthalpyrunsinair,CO ,andCO -N mixtures.
2 2 2
Fig.6 Comparisonofgroundtestandflightconditions. Unfortunately,explicitinformationregardingfreestreamspeciemass
60 HOLLISANDPRABHU
Table3 Forwardreactionratecoefficients
No. Reaction A B C Type Third-partymultiplier Refs.
1 CO(cid:10)M!C(cid:10)O(cid:10)M 2:3(cid:6)1020 (cid:5)1:00 1:29(cid:6)105 Dissociation [28]
2 CO(cid:10)O!O (cid:10)C 3:9(cid:6)1013 (cid:5)0:18 6:92(cid:6)104 Exchange [29]
2
3 CO (cid:10)M!CO(cid:10)O(cid:10)M 1:5(cid:6)1025 (cid:5)2:50 6:60(cid:6)104 Exchange (cid:6)2forM(cid:3)atoms [30]
2
4 CO (cid:10)O!O (cid:10)CO 2:1(cid:6)1013 0.00 2:78(cid:6)104 Dissociation [28]
2 2
5 O (cid:10)M!2O(cid:10)M 2:0(cid:6)1021 (cid:5)1:50 5:94(cid:6)104 Dissociation (cid:6)5forM(cid:3)atoms [29]
2
concentrations is incomplete in the documentation available IV. AssessmentofExperimental–Computational
[18–20].Becauseitwasnotwithinthescopeofthisstudytoperform Comparisons
computationstodeterminefacilityoperatingconditions,thesedata
A. SurfaceHeatTransferComparisons
werenotanalyzed.Ifsuchinformationcouldbeobtained,thesedata
Comparisons were made between the LAURA and DPLR
shouldbefactoredintofuturework.
predictions and the experimental heat transfer data for each test
TheCUBRCLENSAGARD-18testwasconductedona70deg
condition. These comparisons are shown in Figs. 7–17 and are
sphere-cone model in air and N at enthalpies between 5 and
181 10 MJ=kg. Data were obtained [221] on both the blunted-cone odradtae,rendoitnjutesrtmosnofainfaccreilaistyin-bgyt-oftaaclileitnythbalapsyis.ovInerethaechwfihoglueres,etthoef
2 forebodyandinthewakeonaninstrumentedsting.
1.6 experimentaldataareshownwitherrorbarsof(cid:7)15%.Thisvalueis
14/ purely a nominal figure used as a consistent reference and is not
5
0.2 III. ComputationalMethods derivedfrom the published reports; the actual stated experimental
OI: 1 Flowfield solutions were generated at each test condition using uncertainties varied from approximately 5 to 15% as discussed
aa.org | D NnhuyAmpSeerArsi’ocsnaLilcAsUimaReuArloaatthinoednrmDtoPodLoylRsnacemomdiecpslo.TycehodemspebuyctoadNtieoAsnSasrAetahfnoedrtwcooenxpttrieinnmusuaivrmye ptchoreenvdniiootiunoscnlayt.aoFlpyottirioctn,hsef.uclolLymAcpUautRtaaAltyitoinacn,aldarnedDsuPsluLtspR,eprrcreaedtsaiucllyttistoicnwsweaarrelelsbghoeounwnenrdaaflorlyyr
c.ai documentation and background material are available (e.g., [22–
ar
p:// 25])foreachcode.Althoughtherearesomealgorithmicandphysical
htt modeling differences between them, both are structured-grid
3 | Navier–Stokes solvers for flows with vibrational and chemical
1
20 nonequilibrium.Pastcode-to-codecomparisonshavedemonstrated
15, goodagreementbetweenthemforentryvehicleaerothermodynamic
ch simulations relevant to HMMES, such as for the Mars Science
ar
M Laboratory[26]andFireII[27]missions.
on In this study,the physicalmodel employed was that of laminar
RE flow,withtwo-temperature(translationalandvibrational/electronic)
NT representationandnonequilibriumchemicalkinetics.Afive-reaction
E
C chemistry model for the CO -CO-O -O-C system was used, with
CH forward reactions as defined2by the2modified Arrhenius form of
R
A Eq.(1)andbackwardratesdeterminedfromtheequilibriumconstant
E
S definitionvia Eq. (2). The forward reaction coefficients are listed
E
Y R inTable3.Thecarbonatomproducingreactions(nos.1and2)were
E included in this set for completeness; however, these reactions
L
NG were found to be negligible for the range of test conditions
LA considered:
A (cid:2) (cid:3)
S
A cm3
d by N kF(cid:3)A(cid:6)TB(cid:6)exp(cid:8)(cid:5)C=T(cid:9) units of gmol-s (1) F1:i9g.M7J=CkUgBcRasCe.LENS I Reflected Shock Tunnel: Series 2, run 16,
e
ad (cid:2) (cid:3) (cid:2) (cid:3)
Downlo kB(cid:3)KkFC units of gmcmol62-s or gmcmol3-s (2)
For the comparisons with experimental data, the freestream
boundary conditions were taken from the published facility test
conditions. Thewall temperature boundary condition was set to a
constant300Kvalue;althoughheattransferratesforthesecasescan
be very high, the facility run times were in the millisecond to
microsecond ranges, over which time the increase in wall
temperaturewasnegligiblewithrespecttotheboundary-layeredge
temperatures. A surface catalysis boundary condition was also
required.Severalsurfacecatalysismodeloptionswereemployed:a
noncatalytic option, a fully catalytic option (forces atoms to
recombinetohomogenousdiatomics)anda“supercatalytic”option,
in which recombination to 100% CO is enforced at the surface.
2
Thechoiceofwallcatalysismodelhasbeenshowntohavealarge
effectonsensitivityofaeroheatingpredictions[4]but,unfortunately,
asdiscussedin[3],therearelittledataavailableatlowtemperatures
(such as generated in these tests) on catalysis effects for CO
2
reactions to help justify the selection of a particular catalysis Fig.8 CUBRC LENS I Reflected Shock Tunnel: Series 1, run 12,
model. 5:1MJ=kgcase.
HOLLISANDPRABHU 61
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1.6 Fig.9 CUBRC LENS I Reflected Shock Tunnel: Series 2, run 8, Fig.12 Caltech T5 Reflected Shock Tunnel: Run 2256, 6:1MJ=kg
14/ 5:6MJ=kgcase. case.
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AN consistentwithdifferencesbetweenthembeingmuchsmallerthan With the exception of the GASL HYPULSE case (which is the
A L thedifferencesproducedbyselectionofthewallcatalysisboundary highest enthalpy condition), the current comparisons between
AS condition. Thus, to maintain clarity on the plots, only the fully predictions and measurements are similar to the comparisons
y N catalyticDPLRresultswillbeshownalongwiththeLAURAresults previouslypublishedforeachstudy.FortheGASLHYPULSEcase
d b foreachboundarycondition. (Fig.17),thereisalargeoverpredictionofthedatainthecurrentstudy
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Fig.11 CUBRC LENS I Reflected Shock Tunnel: Series 2, run 12, Fig.14 CUBRC LENS I Reflected Shock Tunnel: Series 2, run 13,
6:0MJ=kgcase. 8:6MJ=kgcase.
62 HOLLISANDPRABHU
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1.6 Fig.15 CaltechT5ReflectedShockTunnel:Run2254,10:6MJ=kg
14/ case.
5
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1
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a.or were determined from the definition of the equilibrium constant
a
c.ai (e.g., [32]). When the chemistry models employed in [6–8] were
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01 adiscrepancybetweencurrentandpreviouscomparisons.
2
5, Thedifferencesbetweenpredictionandmeasurementshownfor
h 1 each of the gauges in Figs. 7–17 were averaged for each case to
c
Mar determine an overall uncertainty for that case. Averages were
n generatedforsupercatalyticandnoncatalyticcomparisonintermsof
o
E both the average magnitude (absolute value) of the differences
R
NT betweenpredictionandmeasurementandtheaverageofthesigned
CE (positive/negative) differences. These averages are plotted in
H Figs. 18–21 vs total enthalpy. From these figures, several general
C
AR observationscanbemade:
SE 1) The average magnitude per case of the differences between
E
Y R Fig.16 CaltechT5ReflectedShockTunnel:Run2255,11:3MJ=kg noncatalytic predictions and experimental data varied between 15
LE case. and45%.
G 2) The average magnitude per case of the differences between
N
A supercatalytic predictions and experimental data varied between
A L thatwasnotevidentintheoriginalcomparisons.Thisdifferencewas approximately5and30%,withtheexceptionofa148%difference
AS traced to the chemical–kinetic models employed. In the original fortheGASLHYPULSEcase.Uponreviewofadraftofthispaper
y N study,explicitforwardandbackwardreactionrateswerespecifiedas bytheoperatorsofHYPULSE,‡itwasindicatedthatthepublished
d b perEvansetal.[31],whereasinthecurrentstudy,thebackwardrates resultsfromthistestmaycontainadatareductionerrorthatproduced
e
ad erroneouslyhighheatingvalues.However,timelimitationspreclude
o
wnl reviewingandrevisingthesedatainthepresentpublication.
Do 3)Thenoncatalyticpredictionsaveragedfromapproximately1to
35%lowerthanthedatapercase,expectfortheGASLHYPULSE
casewherethepredictionswere45%higherthanthedata.
4)Thesupercatalyticpredictionsaveragedfrom5to35%higher
thanthedatapercase,withtheexceptionofa148%overprediction
fortheGASLHYPULSEcaseandtheunderpredictionforthelow-
enthalpyCUBRCLENScase.
5)Alinearfitcanbemadeforanyoftheaveragecomparisonsto
showthatthedifferencesincreasewithtotalenthalpy.However,the
qualityofsuchfitsisquestionablegiventhesmallnumberofdata
points available and the skew resulting from the very large
differencesfortheGASLHYPULSEcase.
From these results, it is tempting to conclude that the
supercatalyticboundaryconditionisappropriatebecauseitprovides
theclosestagreementwiththedata,withtheexceptionoftheGASL
HYPULSEcase,whichcouldbeeliminatedasanoutlierpoint(andis
subject to possible revision due to data reduction error as noted
previously).Infact,forNASA’sMSLmission,thisconclusionwas
Fig.17 GASLHYPULSEExpansionTube:(cid:2)12:3MJ=kgcase. ‡FromprivatecommunicationwithChing-YiTsai,ATK(Aug.2011).
HOLLISANDPRABHU 63
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10. Fig.19 Comparisonofnoncatalyticpredictionswithdata(averaged Fig.21 Comparisonofsupercatalyticpredictionswithdata(averaged
OI: signederror). signederror).
D
org | appliedbecausethesupercatalyticoptionprovidesthemostdesign
aa. conservatism[33]. differenceswerealsoobservedinthecomparisonsbetweenpredicted
c.ai However, although possibly appropriate as a vehicle design andmeasuredshockshapes.Suchflowfielddifferencescannotbea
http://ar puanrcaedritgaimnt,ysauncahlysais.cOonthcleurseiovnidecnacnenmotusbtealsaoppbleiecdontsoidaererdig.oFriorsuts, ffuacntcotrisontoocfosnusrifdaecre. catalysis, thus there must be other uncertainty
13 | thatthelimitedsetofdataonCO2surfacecatalysisdonotsupport[3]
20 thesupercatalyticmodelformetallicsurfacesatlowtemperatures.
5, Second,thattheHYPULSEdatawereobtainedonmodelsfabricated B. Shock-ShapeComparisons
1
ch fromMacorceramic, whichwouldbeexpected toshowevenless Comparisons were made between the predicted and measured
Mar catalyticefficiencythanametallicmodel;thus,thistestmayprovide shockshapes(withtheexceptionofCaltechrun2256forwhichno
on adistinctlydifferentphysicalenvironmentthantheothersandcannot image was available) as shown in Figs. 22–30. The differences
RE beimmediatelydismissed.Third,thatthefreestreamenvironmentof betweenpredictedandmeasuredshockstandoffdistancesatthenose
NT theGASLHYPULSEtest(andalsotheUniversityofIllinoisHET areshowninFig.31withrespecttototalenthalpyandinFig.32with
CE test) was generated in a significantly different manner than the respect to freestream density. With the exception of the lowest
CH CUBRCLENS,CaltechT5,andAmes42-InchShockTunneltests; enthalpyCUBRCLENScase(series2,run16)andperhapstheARC
AR thefirsttwofacilitiesoperateasshock-expansiontunnels,whereas 42-Inchcase,therewerelargedifferencesbetweenthepredictedand
SE theotherthreeoperateasreflectedshocktunnels.Asdiscussedin measuredshockshapesforallcases.Shockstandoffdistanceswere
E
Y R [34], there is considerable uncertainty as to the vibrational underpredictedfortheCUBRCLENSandGASLHYPULSEcases
E nonequilibrium state of the freestream in reflected shock tunnels, andoverpredictedfortheCaltechT5andUniversityofIllinoisHET
L
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N
A heattransfermeasurements.Andfinally,aswillbeshowninthenext ARC 42-Inch Shock Tunnel case). These comparisons suggest
L
A section, regardless of surface catalysis model selected, major fundamentaldifferencesbetweenactualandcomputedchemicaland
S
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Fig.20 Comparisonofsupercatalyticpredictionswithdata(averaged Fig.22 CUBRC LENS I Reflected Shock Tunnel: Series 2, run 16,
errormagnitude). 1:9MJ=kgcase.
64 HOLLISANDPRABHU
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aa.org | F5:i6g.M23J=kCgUcBaRseC. LENS I Reflected Shock Tunnel: Series 2, run 8, F6:i0g.M25J=kCgUcBasReC. LENS I Reflected Shock Tunnel: Series 2, run 12,
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13 | htt pwrheedtihceterdthseudrfifafceerehnecaetsiningmraetaessu.rTehduasn,ditprceadnincotetdbheeasatiindgfroartecsewrtaeirne pshreacpiessionforentthrey.cTahseesdiinffetrheinscesstudinypwreedriectmeducahndlamrgeearsuthreadnsthhoocske
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arc conditions are typically determined through a combination of availableforcomparisons.
M diagnosticmeasurementsandnumericalmethods,itisalsopossible
n
E o that the freestream conditions were not accurately characterized.
TR This possibility is more likely for the reflected shock tunnels, as C. OverallAssessmentofComparisons
EN discussedin[14,34]. Withoutattemptingtoassignthecausetoeitherexperimentalor
C
H Although the focus of this study is primarily on heat transfer computational methods, this survey reveals that very large
RC uncertainties,thepredictionofshockshapesalsoaffectsaerodynamic differences exist between the two with respect to convective
ESEA udnisctreirbtauitniotinesa.nTdhtehsuhsoocfktshheafpoercisesananinddmicotomreonftsthreessuulrtfiancgefproremssuthree afleorwohs.eDatiifnfgerreantecsesainndhfleoawttfiraenldsfsehroractkesshvaaprieesdfboerthwigeehn-e1n5thaanldpy14C8O%2
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Y integrationofthatpressuredistribution.Ithasbeenshown[35]that and were strongly influenced by the selection of surface catalysis
LE theuseofdifferentmodels(Camac[36]andMillikan–White[37])for modelsforthecomputations.Shockstandoffdistancecomparisons
G
N vibrationalrelaxationratesofthepolyatomicCO moleculeproduces revealed differences ranging from 50% underprediction to 50%
A 2
L anuncertaintyinthetrimangleofadegreeormorefortheMSL-entry overprediction.
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Fig.24 UniversityofIllinoisHETExpansionTube:5:7MJ=kgcase. Fig.26 ARC42-InchShockTunnel:8:5MJ=kgcase.
HOLLISANDPRABHU 65
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1
25 8:6MJ=kgcase.
10. Fig.29 CaltechT5ReflectedShockTunnel:Run2255,11:3MJ=kg
OI: case
org | D MaTrhseesxepcloomraptiaornismonisssaiorensstamrtulisntgbleypcoonosriadnedretdh.eFirirismt,pilnicahtiisotnosricfoarl
aa. context, is the successful Viking mission. Viking peak heating thepredictedandmeasuredshockshapesdifferindicatesthatother
c.ai conditionswereonthelowrangeofthesedata,wheretheuncertainty phenomena beside wall catalysis are not being modeled properly
http://ar (cid:7)in2h0e%atibnagsemdiognhtthbeeseascsoigmnpeadriaso“nrse.aOsofnfacboluer”sev,anlueiethienrtthheerdaantageseotsf acnodursme,atyheaslesodifcfoernetnricbeusteintsohoacekroshheaaptiensgpruondcuecretaainntiaeesr.odAynnda,moicf
3 | reviewedhereinnorthecomputationaltechniquesemployedexisted uncertainty that cannot be assessed because there are no relevant
201 whenthatmissionwasdeveloped.Instead,analyticalmethodswere force-and-momentdataagainstwhichtocomparepredictions.
5, appliedwithhighlevelsofconservatism. It is a requirement of this study that some numerical values be
1
ch Incontrast,theMSLmission,forwhichmostofthesedatasets assignedtothecomputationalaeroheatinguncertaintyofthestate-of-
Mar were developed, is at the high end of the test range. Noncatalytic the-arttoolsusedbyNASAforMars-entryproblems.Althoughsuch
on predictions were up to (cid:4)35% lower than the experimental data, an assessment is recognized as being overly simplistic, it at least
RE whereas supercatalytic predictions were up to (cid:4)35% higher providesastartingpointforconsiderationoftheissue.Thus,based
NT (exceptingtheGASLHYPULSEcase).Itisfortunatethat,infact,the onthecomparisonspresentedinFigs.7–17,approximateuncertainty
CE supercatalyticmodelwasemployedinthedesignprocessbecauseit estimates for laminar, convective aeroheating have been made in
CH overpredicts all experimental data except a single low-enthalpy terms of total enthalpy. Because of the previously noted doubts
AR condition. astotheappropriatenessofthesupercatalyticboundaryconditions,
SE Looking to the future, HMMES-class missions will experience these estimates are based on the averaged error magnitude
E
EY R emnitshsaiolpnisesarweeolultbsiedyeonthdearnayngeexoisftitnhgetteesstt ddaattaa,.iBteccaanunsoetHsaMfeMlyEbSe reenstuhlatlipnyg(f<ro5mMtJh=ekgn)o,n(cid:7)c1a5ta%lytuicncberotuainndtayr;y2)cfoonrdmitoiodne:ra1te)efnotrhallopwy
GL assumed that the supercatalytic assumption will providesufficient (5–10MJ=kg), (cid:7)30% uncertainty; and 3) for high enthalpy
AN conservatismforaeroheatingpredictions.Additionally,thefactthat (10–20 MJ=kg),(cid:7)60%uncertainty.
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Fig.28 CaltechT5ReflectedShockTunnel:Run2254,10:6MJ=kg Fig.30 GASL HYPULSE Expansion Tube: Run 749, 12:3MJ=kg
case. case.