NASA Technical Reports Server (NTRS) 20140017025: Boundary Layer Transition and Trip Effectiveness on an Apollo Capsule in the JAXA High Enthalpy Shock Tunnel (HIEST) Facility

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by  NASA Technical Reports Server (NTRS)

Boundary Layer Transition and Trip Effectiveness on an Apollo
Capsule in the JAXA High Enthalpy Shock Tunnel (HIEST) Facility
LindsayC.Kirk∗,RandolphP.Lillard†
NASAJohnsonSpaceCenter,Houston,TX77058
JosephOlejniczak‡
NASAAmesResearchCenter,MoffettField,CA94035
HideyukiTanno§
JAXAKakudaSpaceCenter,Kakuda,Miyagi,9811525Japan
ComputationalassessmentswereperformedtosizeboundarylayertripsforascaledApollocapsulemodelinthe
HighEnthalpyShockTunnel(HIEST)facilityattheJAXAKakudaSpaceCenterinJapan. Forstagnationconditions
between2MJ/kgand20MJ/kgandbetween10MPaand60MPa,theappropriatetripsweredeterminedtobebetween
0.2mmand1.3mmhigh, whichprovidedk/δ valuesontheheatshieldfrom0.15to2.25. Thetrippedconfiguration
consistedofaninsertwithaseriesofdiamondshapedtripsalongtheheatshielddownstreamofthestagnationpoint.
Surfaceheatfluxmeasurementswereobtainedonacapsulewitha250mmdiameter,6.4%scalemodel,andpres-
suremeasurementsweretakenataxialstationsalongthenozzlewalls. Atlowenthalpyconditions,thecomputational
predictionsagreefavorablytothetestdataalongtheheatshieldcenterline.However,agreementbecomeslessfavorable
as the enthalpy increases conditions. The measured surface heat flux on the heatshield from the HIEST facility was
under-predictedbythecomputationsinthesecases. Bothsmoothandtrippedconfigurationsweretestedforcompar-
ison, and a post-test computational analysis showed that k/δ values based on the as-measured stagnation conditions
rangedbetween0.5and1.2. Trippedconfigurationsforboth0.6mmand0.8mmtripheightswereabletoeffectively
triptheflowtofullyturbulentforarangeoffreestreamconditions.
I. Introduction
A 6.4% scale model of the Apollo entry capsule was tested in the High Enthalpy Shock Tunnel (HIEST) facility at the
Japan Aerospace Exploration Agency’s Kakuda Space Center (JAXA-KSC). A range of stagnation enthalpy and stagnation
pressureconditionsweretestedtogatherdatatohelpimprovecomputationalsimulationaccuracyathighenthalpyconditions,
toassessboundarylayertripeffectivenessathighenthalpyconditions, andtofurtherinvestigateanomaloussurfaceheatflux
datapreviouslyobtainedintheHIESTfacilityandotherhighenthalpyfacilitiessuchastheT5facilityattheCaliforniaInstitute
ofTechnology2. ThedetailsoftheHIESTtestcampaignwiththeApollocapsuleexaminedinthisworkhavebeenreportedby
Tannoet. al. inaseparatepublication3.
ForreentryvehiclesreturningthroughEarth’satmosphereonhighenergytrajectories,suchasthosefromthemoonorMars,
chemistryeffectsplayasubstantialroleintheaerodynamicheatingtothevehiclesurface**REFERENCE**. Computational
tools are able to predict the heating environments for these high enthalpy conditions where chemistry is important, but the
accuracy of and the uncertainties inherent in these predictions are generally less understood than those of lower enthalpy
conditions because there is less quality validation data available at the higher energy conditions. Ground test facilities are
limited in the conditions that can be reached at higher pressure and enthalpy conditions, so much of the validation data for
flight-like high enthalpy conditions comes from flight test data. Flight test data is able to measure the flight environment,
but understanding the data and quantitatively assessing the uncertainties in computational predictions is hindered by larger
measurement uncertainties such as those due to trajectory uncertainties, instrumentation installation uncertainties, and flight
datareconstructionuncertainties. **ADDMOREHERE**
∗AerospaceEngineer,AIAAMember
†Chief,ThermalDesignBranch
‡Manager,OrionMPCVAerosciences
§Associate Senior Researcher, Space Transportation Propulsion Research and Development Center, Space Transportation Mission Directorates,
[email protected],AIAAmember
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TheanalysispresentedherewillfocusonthecomputationalanalysisofthedataobtainedattheHIESTfacility. Apretest
analysis supported the design of the model and the trip insert, which was comprised of a series of “pizza box” trip elements
andlocateddownstreamofthestagnationpoint. Thepost-testanalysisconsistsofanevaluationofthepredictivecapabilityof
thecapsulesurfacequantitiesforasmoothconfigurationathighenthalpyconditionsandanassessmentoftheeffectivenessof
thetripsthatweredesignedinthepretestanalysis. Anadditionalassessmentoftheaccuracyofthepredictedpressuresonthe
nozzlewallisincludedtohelpunderstandthecomparisonsonthecapsulesurface.
A. HIESTFacilityOverview
TheHIESThighenthalpyfacilityattheJAXA-KSCfacilityisafreepistonshock
tunneldesignedtosimulatetherealgaseffectsathightemperaturessuchasthose
seenbyspacecraftreenteringtheatmosphere1. Thefacilitymeasuresjustover
90 meters in length and has both a conical nozzle and a contoured nozzle to
reach a range of velocities from 3 km/s to 7 km/s. The HIEST can operate at
conditionsuptoamaximumstagnationenthalpyof25MJ/kgandamaximum
stagnation pressure of 150 MPa, and test times are at least 2 msec. Figure 1
showstheshocktubeandinertiamassoftheHIESTfree-pistonshocktunnel.
II. NumericalSimulationMethodology
The computational analysis for this work was performed using the Data-
Parallel Line Relaxation (DPLR)4 software v4.02.2 developed at the NASA
Ames Research Center. DPLR is a finite-volume Navier-Stokes solver that is
capable of modeling thermal and chemical non-equilibrium, both of which are
important for predicting reentry flight conditions and high enthalpy flows in
ground test facilities. All simulations for this analysis were completed using
a five species air chemistry model, and diffusion and transport properties were
modeledusingtheSelf-ConsistentEffectiveBinaryDiffusion(SCEBD)model
and Gupta-Yos transport models, respectively. To reduce complexity, the noz-
zleandcapsulesimulationswererunindependently. Bothsimulations,however,
usedthesamephysicalmodelsinthesimulationforconsistency.
A. NozzleCalculations
Figure1.HIESTShockTubeFacility
Freestream conditions for the Apollo capsule simulations were extracted from
axisymmetricnozzlesimulationswheretheflowwasexpandedthroughthenoz-
zlethroatfromasubsonicartificialwallextension.Theflowforeachrunwasas-
sumedtobeinchemicalequilibriumatthestagnationpressureandenthalpypro-
videdbythetestfacility. Equilibriumconditionsforafive-speciesairchemistry
modelwerecomputedusingChemicalEquilibriumwithApplications(CEA)5.
The grid resolution for the nozzle simulations was 178 cells in the axial direction and 600 cells in the radial direction for a
totalof approximately105,000 cells. Figure2 showsa samplenozzlesimulation fora stagnationpressurefor 45MPa anda
stagnationenthalpyof20MJ/kg.
Astudyofthenozzlewallcatalycitywasperformedusingbothcatalyticandnon-catalyticboundaryconditions.Theresults
showed that, for a case with a stagnation enthalpy of 20 MJ/kg and a stagnation pressure of 20 MPa, the wall catalycity had
littleeffectonthecorefloworthewallboundarylayerparameters,specificallytheheightandmomentumthicknessReynolds
number,Re . Asaresult,allsubsequentnozzlesimulationswererunwithanon-catalyticboundarycondition.
θ
A similar study of the effects of the chosen turbulence model on the core flow was completed using a laminar flow as-
sumptionaswellasaturbulentflowassumptionusingtheSpalart-Allmaras(SA)andShearStressTransport(SST)turbulence
models. Figure3showstheeffectofeachofthesemodelingassumptionsontheMachnumberattheassumedmodellocation.
LittledifferenceintheMachnumberwasobservedbetweenthetwoturbulentsolutions,soallsubsequentsimulationswererun
withtheSSTturbulencemodel.
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Figure2.NozzlesimulationforP0=45MPaandH0=20MJ/kgwithMachnumberontopandtranslationaltemperatureonbottom.
Figure3.NozzleTurbulenceModelEffectonCoreMachNumber
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B. CapsuleCalculations
ThetestarticleusedinthetestserieswasanaxisymmetricidealizedmodeloftheApollocapsulewithheatfluxinstrumentation
along the heatshield centerline and off-centerline on the leeside of the heatshield. All simulations were run with a smooth,
heatshield only, half-body grid to reduce the computational cost. The heatshield only approximation was made due to the
lack of instrumentation on the model backshell, and all conditions were tested at 28◦ angle of attack with no side slip so a
symmetricalsimulationwasalsoanappropriateapproximation. Thisresultedinagridsizeofapproximately2.5Mcells,with
160cellsintheoff-bodydirection.
Thenozzlesimulationsshowedthattheflowatthelocationofthetestarticlewasapproximatelyuniformacrossthenozzle
crosssection,andthiswasseeninFigure3. Asaresult,thefreestreamconditionsforthecapsulesimulationswereextractedat
thenozzlecenterline. Figure4showstheassumedmodellocationwithinthenozzle.
Figure4.Assumedtestarticlelocationwithinthenozzle
Once the freestream conditions for each run were extracted from the nozzle simulations, the capsule simulations were
completed assuming both laminar and turbulent flow assuming an isothermal wall boundary condition of 300 K. Turbulent
simulationswererunwiththeBaldwin-LomaxandSSTturbulencemodels. Thewallboundaryconditionwasinitiallyassumed
to be non-catalytic, but it was also expected that catalytic effects would become more important as the enthalpy increased.
For a higher enthalpy run, H = 20 MJ/kg, at a high stagnation pressure of 40 MPa, an additional simulation with a fully
0
catalytic wall boundary condition was completed for comparison. Figure 5 shows this comparison and the nearly negligible
difference between the wall heat transfer resulting from the non-catalytic boundary condition and that of the fully catalytic
boundary condition. The largest differences, which are still minimal, are seen near the windside shoulder. When comparing
thecomputationalresultstothedatameasuredattheseconditions,bothwallcatalycityassumptionssignificantlyunder-predict
thedata. Fromthisresult,wallcatalycityappearstoprovideasmallamountofuncertaintyinpredictingthesurfaceheatflux
measuredinthetunnel.However,somephenomenonappearstobemissingfromthesimulationsthatiscontributingtothelarge
discrepancybetweenthecomputationalpredictionsandthemeasureddata.Thisresultisconsistentwithsometestingshownby
Marineau,et. al. intheT5highenthalpyfacilityatCalTech2. AdditionalinvestigationattheHIESTfacility,particularlywith
respecttosourcesofradiationthatcouldbecausingthisincreasedheating,iscurrentlyunderwayandresultswillbepublished
atalaterdate.
Asampleofthecapsulesimulationsforahighpressure(P =50MPa)andlowenthalpy(H =10MJ/kg)conditioncanbe
0 0
seeninFigure6. Thelaminarandtwoturbulentsolutionscanbeseeninseparatesurfaceheatfluxmapsinadditiontoaplot
comparingthecomputationalpredictionsalongthecenterlinetothesmoothandtrippeddatameasuredinthetunnel.
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Figure5.Shot2220withNon-catalyticandFullyCatalyticWallBoundaryConditions,H0=20.75MJ/kg,P0=41.54MPa
Figure6.LaminarandturbulentcapsulesimulationsforP0=50MPaandH0=10MJ/kgwithsmoothandtrippedmeasureddatacomparisons.
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III. AnalysisResults
A. BoundaryLayerTripSizingandEffectiveness
Apretestcomputationalanalysiswasperformedtodeterminethetripheightstobemanufacturedfortesting. Tripheightsthat
would effectively cause the flow to transition from laminar to turbulent were desired. A range of stagnation enthalpies and
stagnationpressures,showninTable1,wereconsidered.
Table1.StagnationConditionsUsedinTripSizingStudy
Case P [MPa] H [MJ/kg]
0 0
A 20.0 5.0
B 20.0 10.0
C 20.0 20.0
D 40.0 5.0
E 40.0 10.0
F 40.0 20.0
G 60.0 5.0
H 60.0 10.0
I 60.0 20.0
Figure7showsthecomputedboundarylayerthickness,δ,andmomentumthicknessReynoldsnumber,Re ,onthecapsule
θ
heatshield for the conditions selected. Also noted is the planned location of the trip elements on the test article. Case F was
chosenasthebaselineconditiontosizethetripsforallotherconditions.Table2showsthek/δvalueschosenfortheassessment
aswellastheresultingtripheightsrequiredtoobtainthedesiredk/δ fortheboundarylayerthicknesspredictedforCaseFat
thedesiredtriplocation. Herek istheheightofthetripandk/δ isanon-dimensionalscalingparameterusedtomeasurethe
tripeffectivenessfordifferentflowconditions.
(a) BoundaryLayerThickness (b) BoundaryLayerMomentumThicknessReynoldsNumber,Reθ
Figure7.Boundarylayerparametersusedintripsizingstudy
Table2.CaseFBoundaryLayerScalingParameters,δ=1.103mm
k/δ 0.2 0.3 0.5 0.7 1.0 1.2
k[mm] 0.22 0.33 0.55 0.77 1.10 1.32
From previous experience ***FIND REFERENCES***, the boundary layer is expected to trip at values of k/δ between
0.3and1.0,dependingonthevalueofRe . Thesixtripheightschosenforthistestingprovidedawiderangeofk/δ options
θ
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acrossthedesiredtestconditions. ForCaseCwiththethickestboundarylayer, thelargesttripwouldprovideak/δ valueof
0.86,andforCaseGwiththethinnestboundarylayer,thesmallesttripwouldprovideak/δ valueof0.41,bothofwhichare
withintherangeexpectedtotriptheboundarylayer.
Post-testanalysisshowedawiderangeofk/δ valueswereachievedduringtesting. Boundarylayerthicknessvalueswere
computedbasedontheas-measuredreservoirstagnationconditionsfromthetestingaccordingtotheproceduresdiscussedin
SectionII.Forthelowenthalpy3MJ/kgcondition,a0.6mmtripwasusedandak/δof0.93wasachieved. Asaresultofthe
highk/δ, fullyturbulentflowwasattaineddownstreamofthetrip. However, atahighenthalpyandhighpressurecondition,
(40MPaand20MJ/kg),thetaller0.8mmtripwasnotaseffective. Thek/δvaluecomputedforthesetestconditionswas0.75,
butthelowfreestreamReynoldsnumberof1.8×105,basedontheheatshielddiameter,preventedtheflowfromtransitioning
tofullyturbulentwiththelargetrip.
A high pressure, low enthalpy condition was tested with two different trip heights of 0.6 mm and 0.8 mm. At these
conditions,theboundarylayerwasthinenough(0.7mm)thatbothtripheightseffectivelytrippedtheboundarylayertofully
turbulent. Thesetripsresultedink/δvaluesof0.84and1.13,respectively.
**ANYTRENDSINEFFECTIVENESSVS.RE THETA??***
B. ValidationofCapsuleSurfaceHeatFluxPredictions
ForeachoftheconditionstestedintheHIESTfacilityduringtheApollocapsuletestcampaign,thecomputationalresultsalong
theheatshieldcenterlinewerecomparedwiththeheatfluxdatameasuredinthetunnel.Datawasobtainedforbothsmoothwall
conditionsandtrippedconditions,somewithmultipletripheightsforagivenfreestreamcondition. Table3showsthenozzle
stagnationconditionsexaminedfortheApollocapsuleduringthistestseries,aswellasthecomputedfreestreamconditionsfor
thecapsuleanalysis.
Table3.NozzleStagnationandCapsuleFreestreamConditionsAnalyzedforCapsuleTestSeries
Shot P [MPa] H [MJ/kg] ρ [kg/m3] V [m/s] T [K] T [K] Re ×10−5
0 0 ∞ ∞ ∞ v,∞ D
2216 31.86 6.22 0.0204 3299.33 569.62 606.70 5.497
2218 31.08 3.64 0.0264 2716.69 315.18 479.03 8.875
2220 41.54 20.76 0.0103 5631.80 2190.24 2194.60 1.823
2221 60.02 9.39 0.0278 3986.06 1024.39 1029.62 6.029
2232 12.72 4.63 0.0102 2864.18 368.36 588.61 3.251
2233 15.44 2.98 0.0168 2330.92 206.61 519.36 6.733
One test condition at a low stagnation enthalpy and high stagnation pressure showed natural boundary layer transition
alongtheheatshieldcenterline. Figure9showsthecomparisonofthedatafromshot2218withouttrips,shot2242atsimilar
conditions with an array of trips 0.6 mm tall, as well as the computational simulations for a non-catalytic wall boundary at
laminarandturbulentconditions. Theheatfluxinthelaminarregionpriortotransitionisunder-predictedbythelaminarflow
prediction,andaswasshownpreviously,catalycityhasaminimaleffectonthewallheatfluxattheseconditions,sodifferences
arelikelyduetootherinaccuraciesinthemodeling.
TheturbulentpredictionswereagainperformedwiththeBaldwin-LomaxandSSTturbulencemodels. Thetransitionaldata
fromshot2218betweenz=-0.05mandz=-0.02miswellpredictedbytheSSTturbulencemodel,butthefullyturbulentdata
frombothtestrunsforzgreaterthan0.0misbetterpredictedbytheBaldwin-Lomaxturbulencemodel,butstilloverpredicted
by both models in this region. Due to the complex nature of predicting boundary layer transition, it is likely serendipitous
thatthetransitionlocationandtransitionaldataaresowellpredictedbytheSSTturbulencemodel. Themomentumthickness
Reynoldsnumber,Re ,wasextractedfromtheCFDpredictionatthesensorlastobservedtobelaminar(z=-0.05m).TheRe
θ θ
valuewascomputedtobe76.7,whichislowerthanthetransitionRe valuesobservedinothercapsuletestingfromarangeof
θ
testfacilities6. DatafromhigherenthalpyfacilitiessimilartoHIESTwerealsoincludedinthestudy,althoughwithaCO test
2
gas,butthetransitionRe predictedfordataobtainedinthesefacilitiesagreedwellwiththatofthedataobtainedinfacilities
θ
withanairtestgas.
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Figure8.HeatshieldCenterlineData
Figure9.Shot2218NaturalTransition,H0=3.64MJ/kg,P0=31.08MPa
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C. ComputationalPredictionsofNozzleWallPressure
FortherunsinTable4,pressuresmeasuredataxialstationsalongthenozzlewallwereprovided. Thelocationsofthepressure
sensorscanbeseeninFigure10. Thecomputationalpredictionswereextractedalongthenozzlewallatthesensorlocations
andcomparedtothepressuretracesmeasuredinthetunnel.
Table4.StagnationConditionsAnalyzedforNozzlePressureSensors
Shot P [MPa] H [MJ/kg]
0 0
2341 44.62 20.49
2346 45.05 22.23
2347 56.59 8.05
Figure10.NozzlePressureSensorLocations
Thecomputationalpredictionsfortheseconditionswererunwithasteady-stateassumption,sotherewasnophysicaltime
componenttothesimulations. Forthisreason,atimewhentheshockpassedbythepressuresensorshadtobeassumedforthe
computationalpredictionsinorderforthetestdataandcomputationalpredictionstobecompared. Thistimewasselectedby
examinationofthetimetracesintheexperimentaldataandselectingthetimethattheshockpassedtocorrespondtothefirst
spikeinpressureseeninthefirstpressuresensor. Thistimewasimposedonallsensorsdownthenozzlewithouttakinginto
accounttheshockspeed. Whiletheshockwavemovesquicklydownthenozzle,thetimethattheshockpasseseachsensorwill
vary. Itisrecognized,therefore,thattheassumptionofaconstanttimeofshockpassageforeachsensorisnotaccurate,butis
sufficientforthisanalysis.
Figure 11 shows the comparison of the pressures measured at each of the nozzle sensor locations, shown in the black
lines, with the computationally predicted pressures at the discrete points. The high pressures measured near the throat of
the nozzle are predicted well with the computations, but farther down the nozzle, the predicted pressures are less accurate
andgenerallyoverpredictthemeasurements. **CALCULATEPERCENTAGEDIFFERENCEINPRESSURES**Different
assumptions for catalycity and chemistry models were made in an attempt to understand these differences. However, these
modelingassumptionshadlittleeffectonthepredictedpressures.
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Figure11.Shot2341NozzleWallPressureComparison
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