This article describes a direct comparison between two symmetrical airfoils undergoing dynamic stall at high, unsteady reduced frequencies under otherwise identical conditions. Particle image velocimetry (PIV) was performed to distinguish the differences in flow structure between a NACA 0021 and a NACA 0012 airfoil undergoing dynamic stall. In addition, surface pressure measurements were performed to evaluate aerodynamic load and investigate the effect of laminar separation bubbles and vortex structures on the pressure fields surrounding the airfoils. Airfoil geometry is shown to have a significant effect on flow structure development and boundary layer separation, with separation occurring earlier for thinner airfoil sections undergoing constant pitch-rate motion. Inertial forces were identified to have a considerable impact on the overall force generation with increasing rotation rate. Force oscillation was observed to correlate with multiple vortex structures shedding at the trailing-edge during high rotation rates. The presence of laminar separation bubbles on the upper and lower surfaces was shown to dramatically influence the steady-state lift of both airfoils. Poststall characteristics are shown to be independent of airfoil geometry such that periodic vortex shedding was observed for all cases. However, the onset of deep stall is delayed with increased nondimensional pitch rate due to the delay in initial dynamic-stall vortex.

References

References
1.
Sangwan
,
J.
,
Sengupta
,
T. K.
, and
Suchandra
,
P.
,
2017
, “
Investigation of Compressibility Effects on Dynamic Stall of Pitching Airfoil
,”
Phys. Fluids
,
29
(
7
), p.
076104
.
2.
Tangler
,
J. L.
,
2004
, “
Insight Into Wind Turbine Stall and Post‐Stall Aerodynamics
,”
Wind Energy
,
7
(
3
), pp.
247
260
.
3.
Ericsson
,
L. E.
, and
Reding
,
J. P.
,
1988
, “
Fluid Mechanics of Dynamic Stall—Part 1: Unsteady Flow Concepts
,”
J. Fluids Struct.
,
2
(
1
), pp.
1
33
.
4.
Francis
,
M. S.
, and
Keese
,
J. E.
,
1985
, “
Airfoil Dynamic Stall Performance With Large-Amplitude Motions
,”
AIAA J.
,
23
(
11
), pp.
1653
1659
.
5.
McAlister
,
K. W.
, and
Carr
,
L. W.
,
1979
, “
Water Tunnel Visualisations of Dynamic Stall
,”
ASME J. Fluids Eng.
,
101
(
3
), pp.
376
380
.
6.
Lee
,
T.
, and
Su
,
Y.
,
2015
, “
Surface Pressures Developed on an Airfoil Undergoing Heaving and Pitching Motion
,”
ASME J. Fluids Eng.
,
137
(
5
), p.
051105
.
7.
Poels
,
A.
,
Rudmin
,
D.
,
Benaissa
,
A.
, and
Poirel
,
D.
,
2015
, “
Localization of Flow Separation and Transition Over a Pitching NACA0012 Airfoil at Transitional Reynolds Numbers Using Hot-Films
,”
ASME J. Fluids Eng.
,
137
(
12
), p.
124501
.
8.
Conger
,
R. N.
, and
Ramaprian
,
B. R.
,
1994
, “
Pressure Measurements on a Pitching Airfoil in a Water Channel
,”
AIAA J.
,
32
(
1
), pp.
108
115
.
9.
Jumper
,
E. J.
,
Schreck
,
S. J.
, and
Dimmick
,
R. L.
,
1987
, “
Lift-Curve Characteristics for an Airfoil Pitching at Constant Rate
,”
J. Aircr.
,
24
(
10
), pp.
680
687
.
10.
McAlister
,
K.
,
Pucci
,
S.
,
McCroskey
,
W.
, and
Carr
,
L.
,
1982
, “
An Experimental Study of Dynamic Stall on Advanced Airfoil Section. Volume 2: Pressure and Force Data
,” National Aeronautics and Space Administration, St Louis, MO, Technical Memorandum No.
84245
.https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19830003778.pdf
11.
Butterfield
,
C. P.
,
Hansen
,
A. C.
,
Simms
,
D.
, and
Scott
,
G.
,
1991
, “
Dyanamic Stall on Wind Turbine Blades
,” National Renewable Energy Laboratory, Palm Springs, CA.
12.
Munduate
,
X.
, and
Coton
,
F. N.
,
2000
, “
Identification of Dynamic Stall Regions on Horizontal Axis Wind Turbines
,”
AIAA
Paper No. 2000-0039.
13.
Schreck
,
S. J.
,
Robinson
,
M. C.
,
Maureen Hand
,
M.
, and
Simms
,
D. A.
,
2001
, “
Blade Dynamic Stall Vortex Kinematics for a Horizontal Axis Wind Turbine in Yawed Conditions
,”
ASME J. Sol. Energy Eng.
,
123
(
4
), pp.
272
281
.
14.
Shipley
,
D. E.
,
Miller
,
M. S.
, and
Robinson
,
M. C.
,
1995
, “
Dynamic Stall Occurance on a Horizontal Axis Wind Turbine
,” National Renewable Energy Laboratory, Houston, TX.
15.
Laneville
,
A.
, and
Vittecoq
,
P.
,
1986
, “
Dynamic Stall: The Case of the Vertical Axis Wind Turbine
,”
ASME J. Sol. Energy Eng.
,
108
(
2
), pp.
140
145
.
16.
Müller-Vahl
,
H. F.
,
Nayeri
,
C. N.
,
Paschereit
,
C. O.
, and
Greenblatt
,
D.
,
2016
, “
Dynamic Stall Control Via Adaptive Blowing
,”
Renewable Energy
,
97
, pp.
47
64
.
17.
Müller-Vahl
,
H. F.
,
Strangfeld
,
C.
,
Nayeri
,
C. N.
,
Paschereit
,
C. O.
, and
Greenblatt
,
D.
,
2014
, “
Control of Thick Airfoil, Deep Dynamic Stall Using Steady Blowing
,”
AIAA J.
,
53
(
2
), pp.
277
295
.
18.
Tadjfar
,
M.
, and
Asgari
,
E.
,
2018
, “
Active Flow Control of Dynamic Stall by Means of Continuous Jet Flow at Reynolds Number of 1×106
,”
ASME J. Fluids Eng.
,
140
(
1
), p.
011107
.
19.
Schubel
,
P. J.
, and
Crossley
,
R. J.
,
2012
, “
Wind Turbine Blade Design
,”
Energies
,
5
(
9
), pp.
3425
3449
.
20.
Leishman
,
J. G.
,
2000
,
Principles of Helicopter Aerodynamics
,
2nd ed.
,
Cambridge Aerospace Press
,
New York
.
21.
Panda
,
J.
, and
Zaman
,
K.
,
1992
, “
Experimental Investigation of the Flowfield of an Oscillating Airfoil
,”
AIAA
Paper No. AIAA-92-2622-CP.
22.
Panda
,
J.
, and
Zaman
,
K.
,
1994
, “
Experimental Investigation of the Flow Field of an Oscillating Airfoil and Estimation of Lift From Wake Surveys
,”
J. Fluid Mech.
,
265
(
1
), pp.
65
95
.
23.
Shih
,
C.
,
Lourenco
,
L.
, and
Krothapalli
,
A.
,
1995
, “
Investigation of Flow at Leading and Trailing Edges of Pitching-Up Airfoil
,”
AIAA J.
,
33
(
8
), pp.
1369
1376
.
24.
Shih
,
C.
,
Lourenco
,
L.
,
Van Dommelen
,
L.
, and
Krothapalli
,
A.
,
1992
, “
Unsteady Flow past an Airfoil Pitching at a Constant Rate
,”
AIAA J.
,
30
(
5
), pp.
1153
1161
.
25.
Ol
,
M. V.
,
Bernal
,
L.
,
Kang
,
C.-K.
, and
Shyy
,
W.
,
2009
, “
Shallow and Deep Dynamic Stall for Flapping Low Reynolds Number Airfoils
,”
Exp. Fluids
,
46
(
5
), pp.
883
901
.
26.
Platzer
,
M. F.
,
Jones
,
K. D.
,
Young
,
J.
, and
S. Lai
,
J.
,
2008
, “
Flapping Wing Aerodynamics: Progress and Challenges
,”
AIAA J.
,
46
(
9
), pp.
2136
2149
.
27.
Visbal
,
M.
,
1990
, “
Dynamic Stall of a Constant-Rate Pitching Airfoil
,”
J. Aircr.
,
27
(
5
), pp.
400
407
.
28.
Visbal
,
M.
, and
Shang
,
J.
,
1989
, “
Investigation of the Flow Structure Around a Rapidly Pitching Airfoil
,”
AIAA J.
,
27
(
8
), pp.
1044
1051
.
29.
Visbal
,
M. R.
,
1991
, “
On the Formation and Control of the Dynamic Stall Vortex on a Pitching Airfoil
,”
AIAA
Paper No. 6.1991-6.
30.
Visbal
,
M. R.
,
2011
, “
Numerical Investigation of Deep Dynamic Stall of a Plunging Airfoil
,”
AIAA J.
,
49
(
10
), pp.
2152
2170
.
31.
Visbal
,
M. R.
,
2014
, “
Analysis of the Onset of Dynamic Stall Using High-Fidelity Large-Eddy Simulations
,”
AIAA
Paper No. AIAA 2014-0591.
32.
Young
,
J.
, and
S. Lai
,
J. C.
,
2004
, “
Oscillation Frequency and Amplitude Effects on the Wake of a Plunging Airfoil
,”
AIAA J.
,
42
(
10
), pp.
2042
2052
.
33.
Young
,
J.
, and
S. Lai
,
J. C.
,
2007
, “
Mechanisms Influencing the Efficiency of Oscillating Airfoil Propulsion
,”
AIAA J.
,
45
(
7
), pp.
1695
1702
.
34.
Stevens
,
P.
, and
Babinsky
,
H.
,
2017
, “
Experiments to Investigate Lift Production Mechanisms on Pitching Flat Plates
,”
Exp. Fluids
,
58
(
1
), p.
7
.
35.
Garmann
,
D. J.
, and
Visbal
,
M. R.
,
2017
, “
Analysis of Tip Vortex Near-Wake Evolution for Stationary and Oscillating Wings
,”
AIAA J.
,
55
(
8
), pp.
2686
2702
.
36.
Barlow
,
J. B.
,
Rae
,
W.
, and
Pope
,
A.
,
1999
, “
Low-Speed Wind Tunnel Testing
,”
Wiley
,
New York
.
37.
Raffel
,
M.
,
Willert
,
C.
,
Wereley
,
S.
, and
Kompenhans
,
J.
,
2007
,
Particle Image Velocimetry: A Practical Guide
,
2nd ed.
,
Springer
,
Berlin
.
38.
Westerweel
,
J.
,
2000
, “
Theoretical Analysis of the Measurement Precision in Particle Image Velocimetry
,”
Exp. Fluids
,
29
(
7
), pp.
S003
S012
.
39.
Gibson
,
B. A.
,
2012
, “
Laminar Flow Control of a Flat Plate Boundary Layer Using Dielectric Barrier Discharge Plasma
,”
Ph.D. dissertation
, The University of Adelaide, Adelaide, South Australia.https://core.ac.uk/download/pdf/12795765.pdf
40.
Olsman
,
W.
,
Willems
,
J.
,
Hirschberg
,
A.
,
Colonius
,
T.
, and
Trieling
,
R.
,
2011
, “
Flow Around a NACA0018 Airfoil With a Cavity and Its Dynamical Response to Acoustic Forcing
,”
Exp. Fluids
,
51
(
2
), pp.
493
509
.
41.
Choudhry
,
A.
,
Leknys
,
R.
,
Arjomandi
,
M.
, and
Kelso
,
R.
,
2014
, “
An Insight Into the Dynamic Stall Lift Characteristics
,”
Exp. Therm. Fluid Sci.
,
58
, pp.
188
208
.
42.
Granlund
,
K.
,
Ol
,
M.
,
Garmann
,
D.
,
Visbal
,
M.
, and
Bernal
,
L.
,
2010
, “
Experiments and Computations on Abstractions of Perching
,”
AIAA
Paper No. 2010-4943.
43.
Sayers
,
A.
, and
Ball
,
D.
,
1983
, “
Blockage Corrections for Rectangular Flat Plates Mounted in an Open Jet Wind Tunnel
,”
Proc. Inst. Mech. Eng. Part C
,
197
(
4
), pp.
259
263
.
44.
Hansen
,
K. L.
,
2012
, “
Effect of Leading Edge Tubercles on Airfoil Performance
,” Ph.D. dissertation, The University of Adelaide, Adelaide, South Australia.
45.
Hosseinverdi
,
S.
,
2014
, “
Influence of Free-Stream Turbulence on Laminar-Turbulent Transition in Long Laminar Separation Bubbles: Direct Numerical Simulations
,”
Masters dissertation
, University of Arizona, Tucson, AZ.https://www.researchgate.net/publication/271454420_Influence_of_Free-Stream_Turbulence_on_Laminar-Turbulent_Transition_in_Long_Laminar_Separation_Bubbles_Direct_Numerical_Simulations
46.
Hosseinverdi
,
S.
, and
Fasel
,
H. F.
,
2015
, “
Laminar-Turbulent Transition in a Laminar Separation Bubble in the Presence of Free-Stream Turbulence
,”
Procedia IUTAM
,
14
, pp.
570
579
.
47.
Lourenco
,
L. M.
,
Krothapalli
,
A.
,
Van Dommelen
,
L.
, and
Shih
,
C.
,
1993
, “
Unsteady Flow past a NACA 0012 Airfoil Pitching at Constant Rates
,” Florida Agricultural and Mechanical University, Tellahassee, FL.
48.
Erm
,
L.
,
2003
, “
Measurement of Flow-Induced Pressures on the Surface of a Model in a Flow Visualization Water Tunnel
,”
Exp. Fluids
,
35
(
6
), pp.
533
540
.
49.
Thompson
,
D.
,
1990
, “
Water Tunnel Flow Visualisation of Vortex Breakdown Over the F/a-18
,” Aeronautical Research Laboratories, Melbourne, Australia.
50.
Katz
,
J.
, and
Plotkin
,
A.
,
2001
,
Low-Speed Aerodynamics
,
2nd ed.
, Vol.
13
,
Cambridge University Press
,
New York
.
51.
Gharib
,
M.
, and
Roshko
,
A.
,
1987
, “
The Effect of Flow Oscillations on Cavity Drag
,”
J. Fluid Mech.
,
177
(
1
), pp.
501
530
.
52.
Hudy
,
L. M.
,
Naguib
,
A.
, and
Humphreys
,
W. M.
,
2007
, “
Stochastic Estimation of the Separation-Flow Field Using Wall-Pressure-Array Measurements
,”
Phys. Fluids
,
19
(
2
), p. 024103.
53.
Rival
,
D.
,
Kriegseis
,
J.
,
Schaub
,
P.
,
Widmann
,
A.
, and
Tropea
,
C.
,
2013
, “
A Criterion for Vortex Separation on Unsteady Aerodynamic Profiles
,”
AIAA
Paper No. 2013-0836.
54.
Choudhuri
,
P. G.
,
Knight
,
D.
, and
Visbal
,
M.
,
1994
, “
Two-Dimensional Unsteady Leading-Edge Separation on a Pitching Airfoil
,”
AIAA J.
,
32
(
4
), pp.
673
681
.
55.
Perry
,
A.
, and
Steiner
,
T.
,
1987
, “
Large-Scale Vortex Structures in Turbulent Wakes Behind Bluff Bodies—Part 1: Vortex Formation Processes
,”
J. Fluid Mech.
,
174
(
1
), pp.
233
270
.
56.
McCroskey
,
W.
,
McAlister
,
K.
,
Carr
,
L.
,
Pucci
,
S.
,
Lambert
,
O.
, and
Indergrand
,
R.
,
1981
, “
Dynamic Stall on Advanced Airfoil Sections
,”
J. Am. Helicopter Soc.
,
26
(
3
), pp.
40
50
.
57.
Leishman
,
J.
,
1990
, “
Dynamic Stall Experiments on the NACA 23012 Aerofoil
,”
Exp. Fluids
,
9
(
1–2
), pp.
49
58
.
58.
Heine
,
B.
,
Mulleners
,
K.
,
Joubert
,
G.
, and
Raffel
,
M.
,
2013
, “
Dynamic Stall Control by Passive Disturbance Generators
,”
AIAA J.
,
51
(
9
), pp.
2086
2097
.
59.
Zhou
,
Y.
,
Alam
,
M. M.
,
Yang
,
H.
,
Guo
,
H.
, and
Wood
,
D.
,
2011
, “
Fluid Forces on a Very Low Reynolds Number Airfoil and Their Prediction
,”
Int. J. Heat Fluid Flow
,
32
(
1
), pp.
329
339
.
60.
Huang
,
R. F.
, and
Lin
,
C. L.
,
1995
, “
Vortex Shedding and Shear-Layer Instability of Wing at Low-Reynolds Numbers
,”
AIAA J.
,
33
(
8
), pp.
1398
1403
.
61.
Kim
,
D.-H.
,
Chang
,
J.-W.
, and
Chung
,
J.
,
2011
, “
Low-Reynolds-Number Effect on Aerodynamic Characteristics of a NACA 0012 Airfoil
,”
J. Aircr.
,
48
(
4
), pp.
1212
1215
.
62.
Lin
,
J.-C.
, and
Rockwell
,
D.
,
1996
, “
Force Identification by Vorticity Fields: Techniques Based on Flow Imaging
,”
J. Fluids Struct.
,
10
(
6
), pp.
663
668
.
63.
Anyoji
,
M.
,
Nonomura
,
T.
,
Aono
,
H.
,
Oyama
,
A.
,
Fujii
,
K.
,
Nagai
,
H.
, and
Asai
,
K.
,
2014
, “
Computational and Experimental Analysis of a High-Performance Airfoil Under Low-Reynolds-Number Flow Condition
,”
J. Aircr.
,
51
(
6
), pp. 1864–1872.
64.
Hansen
,
K. L.
,
Kelso
,
R. M.
, and
Dally
,
B. B.
,
2011
, “
Performance Variations of Leading-Edge Tubercles for Distinct Airfoil Profiles
,”
AIAA J.
,
49
(
1
), pp.
185
194
.
65.
Leknys
,
R. R.
,
2013
, “
Investigations Into the Dynamic Stall Characteristics of Airfoils Used in the Wind Turbine Industry Using Flow Visualisation Techniques
,” Masters dissertation, The University of Adelaide, Adelaide, South Australia.
66.
Carr
,
L. W.
, and
Chandrasekhara
,
M.
,
1996
, “
Compressibility Effects on Dynamic Stall
,”
Prog. Aerosp. Sci.
,
32
(
6
), pp.
523
573
.
67.
McCroskey
,
W. J.
,
Carr
,
L. W.
, and
McAlister
,
K. W.
,
1976
, “
Dynamic Stall Experiments on Oscillating Airfoils
,”
AIAA J.
,
14
(
1
), pp.
57
63
.
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