Investigation of Co-Flow Jet Flow Control and its Applications

257 Pages·2015·14.18 MB·English

University of Miami
Scholarly Repository
Open Access Dissertations Electronic Theses and Dissertations
2015-05-05
Investigation of Co-Flow Jet Flow Control and its
Applications
Alexis Michel Lefebvre
[email protected]
Follow this and additional works at:https://scholarlyrepository.miami.edu/oa_dissertations
Recommended Citation
Lefebvre, Alexis Michel, "Investigation of Co-Flow Jet Flow Control and its Applications" (2015).Open Access Dissertations. 1418.
https://scholarlyrepository.miami.edu/oa_dissertations/1418
This Open access is brought to you for free and open access by the Electronic Theses and Dissertations at Scholarly Repository. It has been accepted for
inclusion in Open Access Dissertations by an authorized administrator of Scholarly Repository. For more information, please contact
[email protected].
UNIVERSITYOFMIAMI
INVESTIGATIONOFCO-FLOWJETFLOWCONTROLAND ITSAPPLICATIONS
By
AlexisM.Lefebvre
ADISSERTATION
SubmittedtotheFaculty
ofthe UniversityofMiami
inpartialfulfillment oftherequirements for
thedegree ofDoctorofPhilosophy
CoralGables,Florida
May2015
(cid:2)c 2015
AlexisM.Lefebvre
AllRightsReserved
UNIVERSITYOFMIAMI
Adissertationsubmittedinpartialfulfillment of
the requirementsforthedegreeof
DoctorofPhilosophy
INVESTIGATIONOFCO-FLOWJETFLOWCONTROLAND ITSAPPLICATIONS
AlexisM.Lefebvre
Approved:
GechengZha,Ph.D. NaLi,Ph.D.
Professorof AssistantProfessorof
Mechanical&AerospaceEngineering Mechanical&Aerospace Engineering
AmirRahmani,Ph.D. BertrandDano,Ph.D.
SystemsEngineer ResearchFacultyatFIU
NASAJetPropulsionLaboratory
WeiyongGu,Ph.D. M.BrianBlake,Ph.D.
ProfessorandChairmanof DeanoftheGraduateSchool
Mechanical&AerospaceEngineering
LEFEBVRE,ALEXISM. (Ph.D.,Mechanical&AerospaceEngineering)
Investigation ofCo-FlowJetFlowControlanditsApplications (May2015)
AbstractofadissertationattheUniversity ofMiami.
DissertationsupervisedbyProfessorGechengZha.
No. ofpagesintext. (231)
Thisthesisinvestigatestheperformanceofco-flowjet(CFJ) flowcontrolanditsappli-
cations using experimental testing and computational fluid dynamics (CFD) simulations.
First, the study examines the CFJ energy expenditure, lift enhancement, drag reduction,
stall margin increase, dynamic stall removal, and performance variation with Mach num-
ber. Theseinvestigationsareconductedforavarietyofstationaryairfoils,pitchingairfoils,
and 3D CFJ wings. Then, the CFJ airfoil is applied to design an ultra-high wing loading
generalaviation electricairplane (EA).
For a stationary airfoil and wing, CFJ increases the lift coefficient (C ), reduces the
L
drag and may produce thrust at a low angle of attack (AoA). The maximum lift coefficient
issubstantiallyincreasedfora2DCFJairfoilandreachesavalueof4.8atCμ=0.30. The
powerconsumptionoftheCFJpump,measuredbythepowercoefficient(Pc),isinfluenced
byavarietyofparameters,includingthemomentumcoefficient(Cμ),theAoA,theinjection
slot location, and the internal cavity configuration. A low Cμ of 0.04 produces a rather
small Pc in the range of 0.01 - 0.02 while a higher Cμ rapidly increases the Pc. Due to
thestrongerleadingedgesuctioneffect,increasingtheAoAdecreasesthePc. Thatisuntil
◦ ◦
the flow is nearseparation, within about 2 - 3 of the stall AoA. An injection slot location
within2%-5%chordfromtheleadingedgeveryeffectivelyreducesthepowercoefficient
sincetheleadingedgesuctioneffectistypicallythestrongestwithinthisrange. Aninternal
cavitydesignwithnoseparationiscrucialtominimizetheCFJpowerconsumption. When
the Mach number is increased from 0.03 to 0.3, the suction pressure behind the airfoil
leading edge is lowered due to the compressibility effect. This increases the CFJ airfoil
maximumliftcoefficientanddecreasesthepowercoefficient becauseofthelowerrequired
jet injection pressure. The drag coefficient remains fairly stable within this range of Mach
numbers. At Mach 0.4, as the AoA increases, the flow on the suction surface becomes
transonic. Consequently, a strong λshock wave interrupts the jet and triggers a boundary-
layer separation. The shock wave boundary-layer interaction and wave drag increase the
totaldragandthepowercoefficientsignificantlyduetoalargeincreaseinentropy. Overall,
the CFJ effectiveness is enhanced with an increasing Mach number as long as the flow
remainssubsonic,typicallywithfreestreamMachnumberlessthan0.4.
For a pitching airfoil, CFJ is able to remove the dynamic stall with a substantial lift
increaseanddragdecrease. Twopitchingairfoiloscillationswithdynamicstallarestudied
in this thesis, namely the mild dynamic stall and the deep dynamic stall. At Mach 0.3, the
CFJ with a relatively low Cμ of 0.08 removes the mild dynamic stall. Thereby, the time-
averaged lift is increased by 32% and the time-averaged drag is decreased by 80%. The
resulting time-averaged aerodynamic (L/D) , which does not take the pumping power
ave
into account, reaches 118.3. WhenCμis increased, the time-averaged drag becomes nega-
tive,whichdemonstratesthefeasibilityofaCFJtopropelhelicopterbladesusingitspump
as the only source of power. The deep-stall is mitigated at Cμ = 0.12 and completely re-
moved at Cμ = 0.20 with a great (L/D)ave increase. At Mach 0.4, the CFJ mitigates the
mild dynamic stall. However, the energy consumption is higher than at Mach 0.3 due to
theappearanceofshockwavesintheflow.
A 3D CFJ wing based on NACA 6415 airfoil with an aspect ratio of 20 produces a
maximum L/D of 38.5 at a remarkably high cruise C of 1.20 with an AoA of 5.0◦ and a
L
lowCμof0.04. ThetakeoffandlandingperformanceisalsoexcellentwithamaximumCL
of4.7achievedatCμof0.28andAoAof40.0◦. Whenthewingthicknessisincreasedfrom
15% to 21%, not only the lift is increased by about 5% but the structural strength is also
improved. Overall the CFJ wing efficiency is found to be similar to that of conventional
wings, but the lift coefficient at cruise condition is much higher, typically by 2-3 times.
HenceCFJisparticularly suitabletodesignacompactwingwithhighwingloading.
In the final study of this thesis, a CFJ Electric Aircraft (CFJ-EA) is designed for the
general aviation. The aircraft has a high wing loading so that it can carry more battery
and reach a longer range with a relatively small wing size. The CFJ-EA mission is to
carry 4 passengers at a cruise Mach number of 0.15 with a range of 315nm. The CFJ-EA
cruises at a very high C of 1.3, which produces a wing loading of 182.3kg/m2, about 3
L
timeshigherthanthatofaconventionalgeneralaviationairplane. Todeterminetheaircraft
range and endurance, we introduce the corrected aerodynamic efficiency (L/D) defined
c
as (L/D)c = L/(D+P/V∞), where the L and D are the aerodynamic lift and drag, P is
the CFJ pumping power andV∞ is the free stream velocity. The (L/D)c of the CFJ-EA is
excellentwithacruisevalueof23.5atalowCμof0.04. Takeoffandlandingdistancesare
alsogoodduetoaveryhighmaximumCL of4.8,achievedwithahighCμof0.28. During
takeoffandlanding,thewingpivotsaroundits1/4chordaxissothatitcanachieveanAoA
of 25.0◦ with the fuselage rotated by only 5.0◦. Based on a measure of merit defined as
MPS=Miles*Passengers/S, where S is the wing planform area, the MPS of the present EA
design is about half that of a conventional reciprocating engine general aviation airplane,
and is 1.5 to 2.5 times greater than the MPS of the state of the art EA. This suggests that,
comparedtotheconventionalEA,asamesizeCFJ-EAhasafargreaterrange,orasmaller
CFJ-EA achieves the same range. Therefore, the CFJ-EA concept may open the door to a
new class of general aviation EA designs. The same CFJ airfoil flow control technology
is also suitable for airplanes and rotorcraft using conventional propulsion systems includ-
ing high altitude planform, general aviation, commercial aviation or military transport to
improve therange,reducethe wingsizeand/orreducethe takeoffandlandingdistances.
Dedicated to everyone that shares the passion for Aeronautics
and works for its Excellence
iii
Contents
ListofFigures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
ListofTables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
ListofSymbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
Chapter1 Introduction 1
1.1 Airfoil Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Chronological Evolution . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.2 ModernAirfoil Design . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 HighLiftFlowControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2.1 VortexGenerator . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1.2.2 SlatandFlap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.3 SuctionandBlowing . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.2.4 PlasmaActuator . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
1.2.5 Circulation Control Airfoil . . . . . . . . . . . . . . . . . . . . . . 20
1.2.6 CFJFlowControlMethod . . . . . . . . . . . . . . . . . . . . . . 22
1.3 CFJAirfoil forRotorcraft . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.3.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
1.3.2 Dynamic StallMitigation . . . . . . . . . . . . . . . . . . . . . . . 29
1.3.3 CFJAirfoil, anEffectiveSolutiontoRemoveDynamic Stall . . . . 31
1.4 CFJAirfoil forElectricAircraft . . . . . . . . . . . . . . . . . . . . . . . 31
1.4.1 Environmental Background . . . . . . . . . . . . . . . . . . . . . 33
1.4.2 Electric EnergyStorage . . . . . . . . . . . . . . . . . . . . . . . 34
1.4.3 Propulsive Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.4.4 ANecessaryRevolution ofAircraftTechnology . . . . . . . . . . . 37
1.4.5 CFJGeneralAviationElectricAircraft: ARevolutionary Concept . 39
1.5 Outline andStrategyoftheThesis . . . . . . . . . . . . . . . . . . . . . . 40
Chapter2 TheFluidFlowGoverningEquations 42
2.1 TheNavier-Stokes Equations . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.2 Spalart-AllmarasTurbulence Model . . . . . . . . . . . . . . . . . . . . . 47
Chapter3 NumericalMethodology 52
3.1 Implicit Discretization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.2 Implicit TimeIntegration . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3.3 Gauss-SeidelLineRelaxation . . . . . . . . . . . . . . . . . . . . . . . . . 55
3.4 UserPrescribedCμBoundaryCondition forCFJ . . . . . . . . . . . . . . 56
3.5 ValidationStudy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Chapter4 CFJAirfoilParameters 59
4.1 Lift,DragandMomentCalculation . . . . . . . . . . . . . . . . . . . . . 59
iv