nanosecond dielectric barrier discharge plasma actuator

224 Pages·2016·11.53 MB·English

NANOSECOND DIELECTRIC BARRIER DISCHARGE
PLASMA ACTUATOR
CHARACTERIZATION AND APPLICATION

NANOSECOND DIELECTRIC BARRIER DISCHARGE
PLASMA ACTUATOR
CHARACTERIZATION AND APPLICATION
Proefschrift
terverkrijgingvandegraadvandoctor
aandeTechnischeUniversiteitDelft,
opgezagvandeRectorMagnificusprof.ir.K.C.A.M.Luyben,
voorzittervanhetCollegevoorPromoties,
inhetopenbaarteverdedigenopMaandag8februari2016om10:00uur
door
GiuseppeCORREALE
MasterofScienceinAerospaceEngineering
DelftUniversityofTechnology,TheNetherlands
geborenteNapels,Italië.
Ditproefschriftisgoedgekeurddoordepromotor:
Prof.dr.F.Scarano
Copromotor:Dr.M.Kotsonis
Samenstellingpromotiecommissie:
RectorMagnificus, voorzitter
Prof.dr.F.Scarano, TechnischeUniversiteitDelft,promotor
Dr.M.Kotsonis, TechnischeUniversiteitDelft,copromotor
Independentmembers:
Prof.dr.ir.L.L.M.Veldhuis, TechnischeUniversiteitDelft
Prof.dr.J.Little, ArizonaStateUniversity,US
Prof.dr.J.P.Bonnet, UniversitedePoitiers,FR
Dr.P.Leyland, EcolePolytechniqueFederaledeLausanne,CH
Prof.dr.N.Benard, UniversitedePoitiers,FR
Prof.dr.ir.G.vanBussel, TechnischeUniversiteitDelft,reservelid
v
Keywords: ns-DBDPlasmaActuator
Printedby: IpskampDrukkers
Front&Back: WheatfieldwithCrows,VincentVanGogh
Graphicby:
Copyright©2016byGiuseppeCorreale
ISBN978-94-6186-603-5
Anelectronicversionofthisdissertationisavailableat
http://repository.tudelft.nl/.
Autviaminveniamautfaciam.
Annibale
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S
UMMARY
AN experimental investigation about nanosecond Dielectric Barrier Discharge (ns-
DBD)plasmaactuatorispresentedinthisthesis. Thisworkaimedtoanswerfun-
damentalquestionsontheactuationmechanismofthisdevice. Inordertodoso,para-
metric studies in a quiescent airas wellaslaminar bounded offreeshear layerswere
performed. Amplitudeandlocationoftheinputwithrespecttothereceptivity region
as well as frequency of flow actuation were investigated. This work required the im-
plementation of acquisition techniques such as Schlieren, Particle Image Velocimetry
(PIV),infraredthermography,backcurrentshunttechniqueandbalancemeasurements.
Moreover,toolsofanalysiswereemployedsuchasLinearStabilityTheory(LST),Proper
OrthogonalDecomposition(POD)andInverseHeatTransferProblem(IHTP).
Resultsrevealedthattheeffectofans-DBDisthatof“enhancing”thedevelopment
ofnaturalhydrodynamicinstabilitiesofthespecificfieldofmotion. Therefore,incase
of a laminar boundary layer, the effect of a ns-DBD plasma actuator was to amplify
Tollmien–Schlichting wavesaccordingtolinearstabilitytheory. Suchresultsledtoun-
derstand the influence of the actuator position on the achievement of a specific flow
controltask.
Ans-DBDiscapableofproducingseveraleffects: ashockwave,asmallbodyforce
and a thermal gradient within the discharge volume. Thus, three were the possible
causes of flowactuation. The shock wavewasfound to betoo weakto becapable of
introducinganappreciabledisturbance. Astheshockwave,alsothemomentuminjec-
tioninducedbythebodyforceproducedbythepulseddischargewasfoundtoberela-
tivelytoosmalltojustifyacontrolauthoritybasedonmomentumredistributionwithin
the boundary layer, for cases of relatively high freestream velocity. Thus, the thermal
gradientinducedwithinthedischargevolumebytheenergydepositionofahighvolt-
agenanoseconddischargeistheeffectcapableofinducingarelativelylargedisturbance
intothefieldofmotion.Nevertheless,athermalgradientwithinagaseousflowinduces
twoeffects, itreducesdensityandincreasesviscosity. Atthemomentitisstillunclear
whichofthesetwoeffectsismorerelevant. Onceidentifiedthethermalgradientasthe
maincauseofflowcontrolmechanism,acharacterizationstudywasperformedaimed
toidentifythepropertiesofans-DBDplasmaactuator(thermal,electricalandgeomet-
rical)importanttomaximizetheinducedthermalgradientwithinthedischargevolume.
Ingeneral,ahigherefficiencyisachievedbyastrongdielectricmaterialconcerning
thermalenergydeposition. Abarrierofans-DBDplasmaactuatorshouldbeasthinas
possible.However,thethicknessaffectsalsothelifetimeofthebarrieritself.
NanosecondpulsedDBDplasmaactuatorshaveshowntohavethecapabilitytode-
layleadingedgeseparation. However,intherelevantliterature,aninfluenceoftheac-
tuationfrequencyontheachievedresultsisalwaysreported.Inordertoinvestigatethis
frequency effect, a parametric study ona BackwardFacing Step wasperformed. This
geometrywasselectedbecauseitmimicsafixedpointlaminarseparation,theflowsce-
ix
x SUMMARY
narioofinterest.Suchflowscenarioisunstableathighfrequenciesclosetothestepand
lowfrequencies downstreamthestepanditnaturally developsamostunstable mode
withinit. However,whenaflowisactuated,itsstabilitychanges,sodothemostunsta-
blefrequenciesnaturallydevelopedwithinit.Resultsshowedthattheeffectofactuation
istheredistributionofenergyamongmodesandthattheoptimalfrequencyofactua-
tionmustbebasedonthenewstabilityachievedbytheflowduetotheactuationitself.
Moreover,resultsindicatedthattheoptimalfrequencyofactuationisnotrelatedtothe
mostunstablefrequenciesnaturallypresentwithinthebasenon-actuatedflow.
Amethodtoquantifytheefficiencyofns-DBDsindepositingenergywithinthedis-
chargevolume is proposed. This energy is the one that eventually contributes to the
formationofthethermalgradientresponsibleoftheflowcontrolcapabilitiesshownby
thesedevices. Suchmethodisbasedonsimultaneousimplementationofinfraredther-
mographyandback-currentshunttechniques.Resultsshowedthattheoverallefficiency
ofans-DBDplasmaactuatorisinverselyproportionaltothethicknessofthedielectric
barrier.
Lastpartofthisthesisisconcernedwithademonstrative applicationofans-DBD
plasmaactuatoronatwoelementairfoil,atReynoldsnumbersrangingbetween0.2 106
·
and2 106. Resultsdemonstrateditscapabilitytodelayseparation,increaseliftandre-
·
ducedraginthepoststallregime.Moreover,theplasmaactuatorshowedthecapability
toeliminatebothalaminarbubbleseparationforsmallanglesofattackandthehystere-
sisbehaviouroftheselectedairfoil.
Inconclusion,thisworkshedsomelightontheflowactuationmechanismofans-
DBDplasmaactuatoranddeepeneditsbasicknowledge.