Weather-Adaptive Noise Abatement Procedures

148 Pages·2017·12.28 MB·English

by  Co C. Petersen

Weather-Adaptive
Noise Abatement
Procedures
Using Optimal Control Theory
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Coverphoto:Cessna525CitationCJ1+atNancy-Essey(ENC/LFSN)-photobyFrancois-XavierSimon.
https://www.airliners.net/.
Weather-Adaptive
Noise Abatement
Procedures
Using Optimal Control Theory
by
Co C. Petersen
Toobtainthedegreeof
MasterofScience
inAerospaceEngineering
attheDelftUniversityofTechnology.
tobedefendedpubliclyonFridayOctober19,2018at14:30.
Studentnumber: 4293657
Thesiscommittee: Prof.dr.R.Curran, TUDelft,committeechair
Dr.ir.S.Hartjes, TUDelft,dailysupervisor
Dr.ir.J.Ellerbroek, TUDelft,externalcommitteemember
Anelectronicversionofthisthesisisavailableathttp://repository.tudelft.nl/.

Preface
This report is the result of the Master Thesis study at the department of Air Transport and Operations of
themastertrackControlandOperationsatthefacultyofAerospaceEngineeringoftheDelftUniversityof
Technology.
Inthepastmonths,Ihaveconductedresearchontheinfluenceofvariousweatherconditionsonnoiseopti-
maldepartureprocedures.Toperformthisanalysisatrajectoryoptimisationtoolhasbeendeveloped.Inits
currentform,themultipleobjectiveoptimisationtakesintoaccountthesoundlevelobservedontheground,
andtheeconomicalfactoroffuelusageinitsobjectivefunction.
AsIgrewupinthevicinityofAmsterdamAirportSchiphol,itwasinterestingtomodelthesoundlevelob-
servedinmyhometownwhenaircraftflyby.Beforestartingthisthesis,Inoticedthatthereweresomediffer-
encesinthesoundlevelobservedwhenaircraftontake-offflypastmyhousedependingontheseasonand
thetimeoftheday.Havinganalysedthesoundpropagationinvariousweatherconditions,Icanhappilysay
thatmyearsdidnotdeceiveme.
Withthisreport,itshouldbecomeclearforthereaderwhatthecausesareofthesevariationsinthesound
levelobservedandhowtrajectoriescanbechangedinordertoreducesthesoundlevelsattheobserverde-
pendingontheactualweatherconditions.
Icouldnothavewrittenthisthesiswithoutthehelpofmany.FirstofallIwouldliketothankthemembersof
myexamcommittee:
• Prof.dr.RickyCurran
• Dr.ir.SanderHartjes
• Dr.ir.JoostEllerbroek
Specialthanksgoouttomydailysupervisor,SanderHartjesfortheguidanceduringthethesiswork. Thank
youforremindingmetofirsttaketwostepsbackwardsandanalyseabasicproblem, beforejumpinginto
complicatedproblems. Thankyouforalwayshavingyourofficeopeninorderformetouseyourdesktopto
programinFORTRAN.Ihopeyouenjoyedmycompanyaswell.
InadditionIwouldliketothankdr.ir.H.G.Visser(Dries)forhisattendanceandfeedbackduringthevarious
presentations I have given discussing my progress. Please enjoy your retirement now. Thank you ir. P.C.
Roling(Paul)forattendingmygreenlightpresentationandthefeedback.
Lastbutmostcertainlynotleast, Iwouldliketothankmyfamilyandfriendswhohaveallcontributedin
variouswaystotheresultnowlyingbeforeus.ThankyoumomandomaforthedinnersonMondays!
CoC.Petersen
Delft,October2018
iii

Summary
Inthecoming20years,airtraveldemandisforecastedtodoublethecurrentdemand.Withtheincreasedde-
mand,flightmovementsattheairportwillincreaseaswell.Notonlythemaximumairportthroughputcapac-
itybecomesaconcern,alsothe(future)policiestowardsenvironmentalpollutionsuchasgaseousemissions
andnoisewillformamajorchallenge.
Ifthesoundisunwantedbythereceiver, itisconsideredasnoise. Aircraftnoiseismainlyregardedas
annoyingasitisrepresentedbyloud,singlenoiseeventsofdepartingorlandingaircraft. Theharmcaused
tothehealthbynoiseaswellasthesymptomsobservedareafunctionofsoundlevelandexposuretime.For
example,noiseingeneralcancausefeelingsofdiscomfortsuchasannoyance,anincreasedproductionof
stresshormonesandcancausedeprivationofsleep.
Gaseousemissionarerelatedtotheemissioncharacteristicsoftheengine. Thustoreducethegaseous
emission, enginetechnologyresearchisrequired. Thenegativeeffectsofnoiseemissionscanbereduced
withouttheintroductionofnewtechnology: Thiscanbeachievedbyintroducingoperationalrestrictions.
The most common operational measure in aviation to reduce the effect of environmental noise pollution
isnoiseabatementprocedures. Noiseabatementproceduresarerecommendedflyingtechniquesbasedon
noiseoptimaltrajectories,whichaimatreducingthenoiseimpactonlocalcommunitiesasmuchaspossible.
Noiseabatementproceduresarebasedonnoiseoptimaltrajectories. Thecurrentnoiseabatementproce-
duresarefixedandareusedinanyweathercondition.Howeveratmosphericconditionschangewithvarying
weatherconditions.Thusthepropagationofsoundfromthesoundsourceattheaircrafttotheobserveralso
changes.
PreviousresearchhaveanalysednoiseabatementproceduresinInternationalStandardAtmosphere(ISA)
conditionsinordertodevelopnoiseoptimisedtrajectoriesforaircraft. Furthermore,thechangeintheob-
servedsoundlevelsonthegroundinvaryingweatherconditionshavebeenanalysed.However,theapplica-
tionofweather-adaptivenoiseabatementprocedureshavenotbeenresearchedyet.
This research has been set up in order to analyse whether the implementation of weather-adaptive noise
abatementproceduresresultindifferentnoiseoptimaltrajectoriesindifferentweatherconditions. There-
searchobjectiveistoassesstheinfluenceofweatheronoptimisednoiseabatementdepartureproceduresfor
oneflyover,bydevelopinganoptimisationtoolthatallowsforthesynthesisofweather-adaptivenoiseabate-
mentprocedureswithintheTerminalManoeuvringArea(TMA).
Forthispurpose,theWeather-AdaptiveFlightOptimisationResearchTool(WAFORT)hasbeendeveloped.
Withinthisframework,anAircraftPerformanceModel(APM),soundpropagationmodel,noiseimpactmodel
andGeographicInformationSystem(GIS)iscombinedinthedynamicoptimisationsoftwareGPOPS.Based
ontheproblemstatement,aircraftdata,costfunctionalandinitialguess,thenoiseoptimaltrajectorywith
theminimisedmaximumnumberofexpectedawakeningsisobtainedusingthegradient-basedoptimisation
techniqueOptimalControlTheory(OCT).
Weathervariablesthatinfluencesoundpropagationaretheairtemperature, relativehumidityandthe
wind.
TheAPMismodelledusingBADA4.0. TheBADAholdsadatabasewithperformancecharacteristicsofair-
craft types. Furthermore the aerodynamic forces are related to the pressure and air temperature ratios to
accountfordifferentatmosphericconditions. Theaircraftmechanicsismodelledasapointmass,reducing
thenumberofvariablesintheoptimisation.
ThesourcenoiseleveloftheaircraftisderivedfromtheANPdatabase. CombinedwiththeDopplerfre-
quencyshift,thesoundispropagatedtowardstheobserver.Soundpropagationismodelledusinggeometric
raytracing. Raytracingisindependentoffrequency,reducingcomputationaltime. Refractionismodelled
bydividingtheatmosphereislogarithmicspacedatmosphericlayers. Withtheinclusionofwind,raysmay
berefractedupwardsupwindoftheaircraftduetodecreasingeffectivespeedofsoundlevels. Downwind,
raysarebentdownwardsdiminishingallshadowzones. Thelossesaccountedforinthepropagationmodel
v
vi 0.Summary
includespreadingloss,atmosphericattenuationlossandgroundreflection.Atmosphericattenuationlossis
influencedbyairtemperatureandrelativehumidity,withlargeratmosphericattenuationlossathigheratmo-
sphericattenuationcoefficients. Theatmosphericattenuationcoefficientisfrequencydependent. Ground
reflectionisinfluencedbythegroundsurfacetypeandisfrequencydependentaswell. Theshadowzones
aremodelledtoensurecontinuityforallobservers, whichisrequiredforthegradient-basedoptimisation
scheme.
Noise impact is evaluated using the FICAN dose-response relationship, relating Sound Exposure Level
(SEL)tothemaximumnumberofexpectedawakenings. Theanalysisismadesite-specificbytheGIS,using
thelatestdatafrom2017publishedbyStatisticsNetherlands(CBS).
Agradient-based optimisationtechnique is used as ithasa superior run time over other optimisation
techniques. Using optimal control theory, one composite objective function is evaluated within a couple
secondstominutes.Aninitialguessisrequiredtostarttheoptimisation.
Verificationandvalidationofthesoundpropagationmodelwasperformedbycomparingthesoundlevels
againstthe soundlevels obtained using the Integrated Noise Model (INM), the current standardto evalu-
ateaircraftnoise. Thenewpropagationmodelresultsinlargersoundlevels. Thisiscausedbythedifferent
atmosphericattenuationlossobtainedineachatmosphericlayers. INMemploysaconstant,arithmeticat-
mospherewhichdoesnottakeintoaccountdifferentatmosphericlayers. FurthermoresinceINMdoesnot
modeltheshadowzone, largedifferencesinsoundlevelsareobservedwhenthereceiverisintheshadow
zone.
Inthenewpropagationmodel,largersoundlevelsareobservedwhentheaircraftisflyingawayfromthe
observerduetotheDopplerfrequencyshift. Furthermoretheshiftintheshadowzonelocationisclearly
observedwiththeinclusionofwind. Thin,narrowbandswithvariedsoundlevelsareobservedduetothe
groundreflection,causedbysecondarysoundraysinterferingconstructivelyordestructivelywiththedirect
soundray. Withsoftergroundsurfaces,theeffectofgroundreflectionisdamped,resultinginloweroverall
soundlevelsandsmallergroundreflectionpeaks.
Thegradientsofthenoiseimpactmodelareobtainedusingtheforwardfinitedifferencemethodasauto-
maticderivativeswithmachineprecisionresultedinconvergencedifficulties.
Toanalysetheinfluenceoftheweathervariables,simulationsinvariouswindandatmosphericattenuation
conditions have been performed on two different Standard Instrument Departure (SID) procedures from
AmsterdamAirportSchiphol(AAS):
• Spijkerboor3KdeparturetowaypointANDIK.-Departurefromrunway24insouthwesterndirection,
whereafterasharpturntowardstherightismadetocontinueflightinnortheasterndirection.
• Arnem3EdeparturetowaypointIVLUT.-Departurefromrunway18Linsoutherndirection,followed
byaleftturntowardstheeast.
Thetwodepartureprocedurediffermainlyinthepopulationdensityspreadaroundthedeparturetrackand
inlength. NearlyallaroundthegroundtrackoftheSpijkerboordeparturethereispopulationwhileforthe
Arnemdeparture, thepopulationismainlylocatedattheinitialandfinalpositionofthesimulation. The
Arnemdepartureisalsoshorterinlength,meaningreducedflighttime.
To analyse the separate influences of the weather variables on the fuel usage, the sound propagation and
thenoiseimpact,firsttheweathervariableshavebeenanalysedseparately. Theresultsobtainedforthetwo
departure procedures were compared to the results obtained in International Standard Atmosphere (ISA)
conditions. This was followed by an analysis on actual weather conditions observed in the past months,
whichcombinesthedifferentweatherconditions.
It turned out that the difference in fuel usage, noise propagation and the noise impact in different at-
mosphericconditionscanbepredictedwithrespecttothevaluesobtainedinISAconditions. However,the
noiseoptimaltrajectoryisatrade-offbetweenfuelusageandnoiseimpactperformedbytheoptimisation.
EspeciallyfortheSpijkerboordeparture,unexpectedtrajectorieswereobtainedwhenthedifferentweather
variableswerecombined.
However,convergencedifficultiesforhigherweightingfactorsforthenoiseimpactintheobjectivefunc-
tion,k ,resultedinnotentirelynewnoiseoptimaltrajectories.Mostoftheobtainednoiseoptimaltrajec-
noise
toriescanbeconsideredasslightadaptationsonthehorizontal,verticalandvelocityprofileinISAconditions.
vii
Theinitialsearchrangeoftheoptimisationisbasedontheinitialguess. Initialguessesoftrajectoriesflying
aroundcitieswithlargerpopulationdensity,convergestowardseitherthesolutionpresentedinthespecific
caseorthethresholdoffeasibilityoroptimallycouldnotbeobtained.
Whenanalysingconvergencebehaviour, itisobservedthatforatmosphericconditionsinwhichrelatively
high sound levels are obtained, the weighting value of noise in the objective function k has been in-
noise
creaseduntilthenormalisedParetofrontsshowasatisfactorycurveinwhichawakeningsareonlyslightly
decreasedwithlargeincreaseinfuelusage. Onereasonforthisbehaviourmightbetheshapeoftheobjec-
tivefunction.Thehighersoundlevelsarepenalisedmoreduetotheincreasednumberofawakeningsinthe
objectivefunction.
Atlowersoundlevels,theoptimisationmightbedeceivedbytheincreasedsoundlevelsduetogroundre-
flection.Thegroundreflectioninducesthinnarrowbandswithincreasingordecreasingsoundlevels.When
alargepopulationgridpointislocatedexactlywithinthepeaks,theoptimisationisstuckandconvergence
difficultiesarise.Withincreasingk values,thiseffectisstrengthened.
noise
Forsimulationswiththeinclusionofwind,theshadowzonemightalsobeasourceoftheconvergence
difficulties. When entering the shadow zone, initially the sound level drops linearly. Although the loss is
modelledcontinuously,thesecondorderderivative,theHessian,isnotcontinuous.Incaseofstrongerwind
velocities, the shadow zone upwind of the aircraft moves closer to the aircraft due to the change in local
speedofsound. Againwhenalargepopulationgridpointislocatedneartheboundaryoftheilluminated
andshadowzone,convergenceissuesmightbeencountered.
Furthermoretheset-upofthecasesinfluencetheconvergence.AstheArnemdepartureisveryrestricted
bythepopulationspread,noiseoptimaltrajectorieswithlowerk valuearealsothenoiseoptimaltrajec-
noise
toryforlargerk values.ThislimitsthenumberofdatapointsontheParetofront,resultinginnon-smooth
noise
normalisedParetofronts.
Basedonthesefindings,itisconcludedthattheweather-adaptivenoiseabatementprocedureswillbenefit
thelocalcommunity. Itisnotedthatthefueloptimaltrajectoryevaluatedinthisstudyismorefuelefficient
thanthecurrentprocedures. Thusthelimitedincreaseinfuelusageoverthefueloptimaltrajectorydoes
notnecessarilyincreasethecurrentfuelusage. Furthermoreasnoentirenewtrajectoriesareobtained,the
implementationofweather-adaptivenoiseabatementproceduresshouldnotintroducemanydifficultiesfor
bothcockpitcrewandairnavigationserviceproviders.
Limitationsoftheanalysisperformedinthisresearchisthatonlyoneaircrafttypehasbeensimulated,noac-
tualmeasurementsinthefieldhavebeenperformed,theuseofFICANdose-responserelationshipasnoise
criterion,andtheuseofgradient-basedoptimisationincombinationwithaninitialguesstostarttheopti-
misation. Differentaircrafttypeshavedifferentsourcenoiseandperformance,resultingindifferentnoise
optimaltrajectories. Furthermorethenoiseimpactisbasedonthemaximumexpectednumberofawaken-
ings.Asthisisafictionalvalue,itmightbedifficulttocommunicatethevaluetooutsiders.
RecommendationsforfurtherimprovementstotheWAFORTincludemoreaccurateandflyabletrajecto-
ries,moreaccuratemodellingoftheatmosphereandatmosphericproperties,modellingoftheaircraftand
sound source as rigid models and the modelling of more accurate flow resistivity per ground surface. Fly
abilityisimprovedbyimplementingareanavigation.
Forfuturework,itisinterestingtoenhancetheWAFORToptimisationschemewithanevolutionaryal-
gorithmtoobtaintheglobalminimum,thedefinitionofamultiplenoiseeventproblemandthecreationof
arunwayallocationproblemfromanairportperspective. TheWAFORTinitscurrentformcanbeusedto
identifyatmosphericconditionsinwhichitisofinteresttoemployweather-adaptivenoiseabatementpro-
cedures.Usingtheevolutionaryalgorithm,theglobaloptimumandthusthemostnoiseoptimaltrajectories
canbeobtained.Asthetotalnumberofawakeningsareverymuchinfluencedbytheatmosphericconditions,
arunwayallocationproblemtominimisenoisefortheentirecommunityaroundtheairportmightresultin
interestingnewnoisepreventingfindings.