The results of stereo particle-image-velocimetry (PIV) measurements are presented in this paper to gain further insight into the wake of a finite width Gurney flap. It is attached to an FX 63-137 airfoil which is known for a very good performance at low Reynolds numbers and is therefore used for small wind turbines and is most appropriate for tests in the low speed wind tunnel presented in this study. The Gurney flaps are a promising concept for load control on wind turbines but can have adverse side effects, e.g., shedding of additional vortices. The investigation focuses on frequencies and velocity distributions in the wake as well as on the structure of the induced tip vortices. Phase-averaged velocity fields are derived of a proper-orthogonal-decomposition (POD) based on the stereo PIV measurements. Additional hot-wire measurements were conducted to analyze the fluctuations downstream of the finite width Gurney flaps. Experiments indicate a general tip vortex structure that is independent from flap length but altered by the periodic shedding downstream of the flap. The influence of Gurney flaps on a small wind turbine is investigated by simulating a small 40 kW turbine in QBlade. They can serve as power control without the need of an active pitch system and the starting performance is additionally improved. The application of Gurney flaps implies tonal frequencies in the wake of the blade. Simulation results are used to estimate the resulting frequencies. However, the solution of Gurney flaps is a good candidate for large-scale wind turbine implementation as well. A FAST simulation of the NREL 5 MW turbine is used to generate realistic time series of the lift. The estimations of control capabilities predict a reduction in the standard deviation of the lift of up to 65%. Therefore, finite width Gurney flaps are promising to extend the lifetime of future wind turbines.

References

References
1.
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2011
, “
Performance Optimization of Wind Turbine Rotors With Active Flow Control
,”
ASME
Paper No. GT2011-45493.
2.
Barlas
,
T. K.
, and
van Kuik
,
G. A. M.
,
2010
, “
Review of State of the Art in Smart Rotor Control Research for Wind Turbines
,”
Prog. Aerosp. Sci.
,
46
(
1
), pp.
1
27
.
3.
Standish
,
K. J.
, and
van Dam
,
C. P.
,
2005
, “
Computational Analysis of a Microtab-Based Aerodynamic Load Control System for Rotor Blades
,”
J. Am. Helicopter Soc.
,
50
(
3
), pp.
249
258
.
4.
Baker
,
J. P.
,
Standish
,
K. J.
, and
Van Dam
,
C. P.
,
2005
, “
Two-Dimensional Wind Tunnel and Computational Investigation of a Microtab Modified S809 Airfoil
,”
AIAA
Paper No. 2005-1186.
5.
Eisele
,
O.
,
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2011
, “
Experimental Investigation of Dynamic Load Control Strategies Using Active Microflaps on Wind Turbine Blades
,”
European Wind Energy Association (EWEA 2011)
,
Brussels
,
Belgium
, Mar. 14–17, pp. 43–47.
6.
Bach
,
A. B.
,
Holst
,
D.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2013
, “
Transitional Effects of Active Micro-Tabs for Wind Turbine Load Control
,”
ASME
Paper No. GT2013-94369.
7.
Mayda
,
E. A.
,
Van Dam
,
C. P.
, and
Yen Nakafuji
,
D.
,
2005
, “
Computational Investigation of Finite Width Microtabs for Aerodynamic Load Control
,”
AIAA
Paper No. 2005-1185.
8.
Holst
,
D.
,
Bach
,
A. B.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2013
, “
Influence of a Finite Width Micro-Tab on the Spanwise Lift Distribution
,”
ASME
Paper No. GT2013-94381.
9.
Althaus
,
D.
,
1996
, Niedriggeschwindigkeitsprofile: Profilentwicklungen und Polarenmessungen im Laminarwindkanal des Instituts für Aerodynamik und Gasdynamik der Universität Stuttgart. Aus dem Programm Strömungsmechanik. Vieweg, Braunschweig/Wiesbaden, Germany.
10.
Selig
,
M. S.
, and
McGranahan
,
B. D.
,
2004
, “
Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbines
,”
ASME J. Sol. Energy Eng.
,
126
(
4
), pp.
986
1001
.
11.
Huber
,
A. F.
, and
Mueller
,
T. J.
,
1987
, “
The Effect of Trip Wire Roughness on the Performance of the Wortmann FX 63-137 Airfoil at Low Reynolds Numbers
,”
Exp. Fluids
,
5
(
4
), pp.
263
272
.
12.
Selig
,
M. S.
, and
McGranahan
,
B. D.
,
2003
, “
Wind Tunnel Aerodynamic Tests of Six Airfoils for Use on Small Wind Turbines
,” National Renewable Energy Laboratory, Golden, CO, Technical Report No. NREL/SR-500-34515.
13.
Migliore
,
P.
, and
Oerlemans
,
S.
,
2004
, “
Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines
,”
ASME J. Sol. Energy Eng.
,
126
(
4
), pp.
974
985
.
14.
Lumley
,
J. L.
,
1967
, “
The Structure of Inhomogeneous Turbulence
,”
Atmospheric Turbulence and Radio Wave Propagation
,
A. M.
Yaglom
and
V. I.
Tatarski
, eds., Nauka, Moscow, pp.
166
178
.
15.
Berkooz
,
G.
,
Holmes
,
P.
, and
Lumley
,
J. L.
,
1993
, “
The Proper Orthogonal Decomposition in the Analysis of Turbulent Flows
,”
Annu. Rev. Fluid Mech.
,
25
(
1
), pp.
539
575
.
16.
Holmes
,
P.
,
Lumley
,
J. L.
, and
Berkooz
,
G.
,
1996
,
Turbulence, Coherent Structures, Dynamical Systems, and Symmetry
,
Cambridge University Press
, Cambridge, UK.
17.
Luchtenburg
,
D. M.
,
Noack
,
B. R.
, and
Schlegel
,
M.
,
2009
, “
An Introduction to the POD Galerkin Method for Fluid Flows With Analytical Examples and MATLAB Source Codes
,” Technische Universität Berlin, Berlin, Technical Report No. 01/2009.
18.
Cordier
,
L.
, and
Bergmann
,
M.
,
2003
, “
Proper Orthogonal Decomposition: An Overview
,”
Post-Processing of Experimental and Numerical Data
(VKI Lecture Series 2003-04), Karman Institute for Fluid Dynamics, Rhode-St-Genese, Belgium.
19.
Cordier
,
L.
, and
Bergmann
,
M.
,
2003
, “
Two Typical Applications of POD Coherent Structures Education and Reduced Order Modelling
,” Post-Processing of Experimental and Numerical Data (VKI Lecture Series 2003-4), von Karman Institute for Fluid Dynamics, Rhode-St-Genese, Belgium.
20.
Sirovich
,
L.
,
1987
, “
Turbulence and the Dynamics of Coherent Structures. Part I–III
,”
Quarterly of Applied Mathematics
,
XLV
(3), pp.
561
590
.
21.
Van Oudheusden
,
B. W.
,
Scarano
,
F.
,
Van Hinsberg
,
N. P.
, and
Watt
,
D. W.
,
2005
, “
Phase-Resolved Characterization of Vortex Shedding in the Near Wake of a Square-Section Cylinder at Incidence
,”
Exp. Fluids
,
39
(
1
), pp.
86
98
.
22.
Bechert
,
D. W.
,
Meyer
,
R.
, and
Hage
,
W.
,
2000
, “
Drag Reduction of Airfoils With Miniflaps. Can We Learn From Dragonflies?
,”
AIAA
Paper No. 2000-2315.
23.
Troolin
,
D. R.
,
Longmire
,
E. K.
, and
Lai
,
W. T.
,
2006
, “
Time Resolved PIV Analysis of Flow Over a NACA 0015 Airfoil With Gurney Flap
,”
Exp. Fluids
,
41
(
2
), pp.
241
254
.
24.
Troolin
,
D. R.
,
Longmire
,
E. K.
, and
Lai
,
W. T.
,
2006
, “
The Effect of Gurney Flap Height on Vortex Shedding Modes Behind Symmetric Airfoils
,”
13th International Symposium on Applications of Laser Techniques to Fluid Mechanics
, Lisbon, Portugal, June, 26–29.
25.
Wagner
,
S.
,
Barei
,
R.
, and
Guidati
,
G.
,
1996
,
Wind Turbine Noise
,
Springer
,
Berlin
.
26.
Bach
,
A. B.
,
Berg
,
R.
,
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2015
, “
Experimental Investigation of the Aerodynamic Lift Response of an Active Finite Gurney Flap
,”
AIAA
Paper No. 2015-1270.
27.
Bach
,
A. B.
,
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2015
, “
Wake Vortex Field of an Airfoil Equipped With an Active Finite Gurney Flap
,”
AIAA
Paper No. 2015-1271.
28.
Müller
,
G.
, and
Möser
,
M.
, eds.,
2012
,
Handbook of Engineering Acoustics
,
Springer
, Berlin.
29.
Marten
,
D.
,
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2010
, “
Integration of a WT Blade Design Tool in XFOIL/XFLR5
,”
10th German Wind Energy Conference (DEWEK 2010)
,
Bremen
,
Germany
, Nov. 17–18.
30.
Marten
,
D.
,
2014
, “
QBlade
,” Technische Universität Berlin, Berlin, http://fd.tu-berlin.de/en/research/projects/wind-energy/qblade/, December.
31.
Gasch
,
R.
, and
Twele
,
J.
, eds.,
2012
,
Wind Power Plants: Fundamentals, Design, Construction and Operation, Electrical Engineering
,
Springer
, Berlin.
32.
Jonkman
,
J.
,
Butterfield
,
S.
,
Musial
,
W. P.
, and
Scott
,
G.
,
2009
, “
Definition of a 5-MW Reference Wind Turbine for Offshore System Development
,” National Renewable Energy Laboratory, Golden, CO, Technical Report No. NREL/TP-500-38060
.
33.
Weinzierl
,
G.
,
Pechlivanoglou
,
G.
,
Nayeri
,
C. N.
, and
Paschereit
,
C. O.
,
2012
, “
Performance Optimization of Wind Turbine Rotors With Active Flow Control: Part 2—Active Aeroelastic Simulations
,”
ASME
Paper No. GT2012-69200.
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