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Airfoil boundary-layer control through pulsating jets [Elektronische Ressource] / vorgelegt von Álvaro Pereira Coppieters

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Airfoil Boundary-Layer Control throughPulsating JetsVom Fachbereich Maschinenbauan der Technischen Universita¨t DarmstadtzurErlangung des Grades eines Doktor-Ingenieurs (Dr.-Ing.)genehmigteD i s s e r t a t i o nvorgelegt von´M. Sc. Alvaro Pereira Coppietersaus S˜ao Paulo, BrasilienBerichterstatter: Prof. Dr.-Ing. B. StoffelMitberichterstatter: Prof. Dr.-Ing. C. TropeaTag der Einreichung: 03.05.2010Tag der Mundlichen Prufung: 16.06.2010¨ ¨Darmstadt 2011D17Hiermit versichere ich, die vorliegende Doktorarbeit unter der Betreu-ung von Prof. Dr.-Ing. B. Stoffel nur mit den angegebenen Hilfsmittelnselbstaendig angefertigt zu haben.´Alvaro Pereira Coppieters Darmstadt, den 18.04.2010AcknowledgmentI would like to thank the people that have been involved in making thiswork possible.My parents, Isabel and Percival who gave me the motivation to go forthings in life I think have to be done. My wife Alice, who have beenalways on my side and gave me the support I needed along this way.My advisor Professor Dr.-Ing. Bernd Stoffel, for giving me this opportu-nity. His motivation and patience have proved invaluable in helping mecomplete this work. I would like to mention Mr. B. Matyschok and Pro-fessor Dr.-Ing. P. Peltz from FST and Mrs. S. Wallner for her goodwill.I would also like to thank Mr. U. Trometer and Mr. A. Schuler from theworkshop, whose ability permited to implement the concepts developedduring this work.

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Published 01 January 2011
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Airfoil Boundary-Layer Control through
Pulsating Jets
Vom Fachbereich Maschinenbau
an der Technischen Universita¨t Darmstadt
zur
Erlangung des Grades eines Doktor-Ingenieurs (Dr.-Ing.)
genehmigte
D i s s e r t a t i o n
vorgelegt von
´M. Sc. Alvaro Pereira Coppieters
aus S˜ao Paulo, Brasilien
Berichterstatter: Prof. Dr.-Ing. B. Stoffel
Mitberichterstatter: Prof. Dr.-Ing. C. Tropea
Tag der Einreichung: 03.05.2010
Tag der Mundlichen Prufung: 16.06.2010¨ ¨
Darmstadt 2011
D17Hiermit versichere ich, die vorliegende Doktorarbeit unter der Betreu-
ung von Prof. Dr.-Ing. B. Stoffel nur mit den angegebenen Hilfsmitteln
selbstaendig angefertigt zu haben.
´Alvaro Pereira Coppieters Darmstadt, den 18.04.2010Acknowledgment
I would like to thank the people that have been involved in making this
work possible.
My parents, Isabel and Percival who gave me the motivation to go for
things in life I think have to be done. My wife Alice, who have been
always on my side and gave me the support I needed along this way.
My advisor Professor Dr.-Ing. Bernd Stoffel, for giving me this opportu-
nity. His motivation and patience have proved invaluable in helping me
complete this work. I would like to mention Mr. B. Matyschok and Pro-
fessor Dr.-Ing. P. Peltz from FST and Mrs. S. Wallner for her goodwill.
I would also like to thank Mr. U. Trometer and Mr. A. Schuler from the
workshop, whose ability permited to implement the concepts developed
during this work.
My friends at TU-Darmstadt, Michael Heß, Kai-Henning Brune, Sven
Koenig, Pascal Schuler, Matthias Puff, Nuri Hamadeh, Val´erie Bischof,
Christian Mu¨ller and Anandarajah Mariadas.
Lastly, the support of the CAPES (Brazil) for the scholarship.This achievement is dedicated to my wife Alice and our children Andr´e
and Ana Ju´lia.Contents
1 Introduction 1
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Previous Research - Literature Review . . . . . . . . . . . . . . . . . . . . 4
1.3 Problem Statement and Purpose of Present Work . . . . . . . . . . . . . . 9
1.4 Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2 Boundary-Layer Theory and Separation Control 11
2.1 Flow Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.1 Laminar Separation . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.1.2 Separation Bubbles . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
2.1.3 Turbulent Separation . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2.1.4 Airfoil Stall . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
2.2 Separation Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
2.2.1 Passive Flow Control Strategies . . . . . . . . . . . . . . . . . . . . 20
2.2.2 Active Flow Control Strategies . . . . . . . . . . . . . . . . . . . . 22
3 Experimental Methods and Facility 29
3.1 Facility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.1.1 Low Speed Wind-Tunnel . . . . . . . . . . . . . . . . . . . . . . . . 29
3.1.2 NACA 63 -018 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
3.1.3 Actuator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3.2 Experimental Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.1 Hot-Wire Anemometry . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.2.2 Particle Image Velocimetry. . . . . . . . . . . . . . . . . . . . . . . 40
3.2.3 Static Pressure Distribution . . . . . . . . . . . . . . . . . . . . . . 44
3.3 Data Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
i3.4 Uncertainty Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.1 Uncertainty of Experimental Results . . . . . . . . . . . . . . . . . 53
4 Calibration of the Actuator 56
5 Results 65
5.1 Tests Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
5.2 Static Pressure Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.2.1 Pressure Distribution - Active Control at α = 17,1 . . . . . . . . . 69
5.2.2 Pressure Distribution - Active Control at α = 18,9 . . . . . . . . . 72
5.3 Flow Field Measurements - PIV . . . . . . . . . . . . . . . . . . . . . . . . 75
5.4 Boundary-Layer Measurements - Hot-Wire . . . . . . . . . . . . . . . . . . 91
5.4.1 Time Averaged Velocity . . . . . . . . . . . . . . . . . . . . . . . . 91
6 Conclusion 97
iiNomenclature
Symbols
2A m projection of an area in a plane paralel to the flow
b m width of slot for air injection
c m airfoil chord or general body characteristic length
C - momentum coefficientμ
c - steady component of Cμ μ
0c - unsteady component of Cμμ
C - drag coefficientD
C - skin friction coefficientf
C - lift coefficientL
C - pressure coefficientp
d mm distance from slot to trailing edge
F N total drag forceD
f Hz frequency
+f - non-dimensional actuation frequency
f - characteristic frequencyc
H - shape factor
l mm slot length
Ma - Mach number
Nu - Nusselt number
p Pa static pressure
p Pa total pressure0
pr - ratio of compressed air line pressure and ambient pressure
Re - Reynolds number
iiiRe - critical Reynolds numbercrit
Re ∗ - Reynolds number based on displacement thicknessδ
Re - Reynolds number based on momentum thickness at the transition onsetθt
Re - Reynolds number based on a general positionx
Re - Reynolds number at the transition onsettr
s m airfoil span
t s time
Tu - turbulence level
u m/s velocity
0u m/s unsteady component of u
+u - nondimensional velocity
u¯ m/s mean velocity
u m/s amplitute of the unsteady jet velocity cycleA
u m/s velocity of main stream1
u m/s flow velocity at the boundary layer edgee
u m/s velocity of air jet from the actuator slot (instantaneous)j
u¯ m/s mean velocity velocity of air jet from the actuator slotj
v m/s component of velocity in the y-direction
x m general position
+y - wall unit
Greek Letters
α grad angle of attack
δ mm boundary layer thickness
δ mm displacement thickness
η - nondimensional wall distance
γ - intermittency factor
γ - fraction of forward flow in the viscous sublayerp
λ - Pohlhausen pressure gradient parameter
λ - Thwaites pressure gradient parameterθ
μ kg/ms dynamic viscosity
iv2ν m /s kinematic viscosity
φ m/s fit coefficient used for the calibration of the actuator
3ρ kg/m density
τ - duty cycle of the solenoid valve
2τ N/m shear stress in the ij planeij
2τ N/m wall shear stressw
θ mm momentum thickness
ζ m/s fit coefficient used for the calibration of the actuator
Abbreviation
AFC Active Flow Control
DNS Direct Numerical Simulation
IA Interrogation Area
IGV Inlet Guide Vane
LDA Laser Doppler Anemometry
LPT Low Pressure Turbine
NACA National Advisory Committee for Aeronautics
PIV Particle Image Velocimetry
PFC Passive Flow Control
RANS Reynolds Average Navier-Stokes
RMS Root Mean Square
vList of Tables
2.1 Aspects of Passive Flow Control methods. . . . . . . . . . . . . . . . . . . 19
2.2 Aspects of Active Flow Control methods. . . . . . . . . . . . . . . . . . . . 19
3.1 Actuation cycles recorded for each actuation frequency (f = 5 kHz). . . 48acq
3.2 Uncertainty of measured variables. . . . . . . . . . . . . . . . . . . . . . . 55
5.1 Range of active control parameters used in the tests. . . . . . . . . . . . . 68
5.2 Test cases examined with PIV at angles of attack α = 17,1 and 18,9 . . . 75
5.3 Test cases examined with HW anemometry at α = 18,9 . . . . . . . . . . . 91
vi