Technical Brief

Trapped Cylindrical Flow With Multiple Inlets for Savonius Vertical Axis Wind Turbines

[+] Author and Article Information
Aaron S. Alexander

Department of Engineering Technology,
Oklahoma State University,
567 Engineering North,
Stillwater, OK 74078
e-mail: aaron.s.alexander@okstate.edu

Arvind Santhanakrishnan

Department of Mechanical and Aerospace Engineering,
Oklahoma State University,
218 Engineering North,
Stillwater, OK 74078
e-mail: askrish@okstate.edu

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 25, 2017; final manuscript received September 22, 2017; published online December 4, 2017. Assoc. Editor: Matevz Dular.

J. Fluids Eng 140(4), 044501 (Dec 04, 2017) (7 pages) Paper No: FE-17-1117; doi: 10.1115/1.4038166 History: Received February 25, 2017; Revised September 22, 2017

Savonius vertical axis wind turbines (VAWTs) typically suffer from low efficiency due to detrimental drag production during one half of the rotational cycle. The present study examines a stator assembly created with the objective of trapping cylindrical flow for application in a Savonius VAWT. While stator assemblies have been studied in situ around Savonius rotors in the past, they have never been isolated from the rotor to determine the physics of the flow field, raising the likelihood that a moving rotor could cover up deficiencies attributable to the stator design. The flow field created by a stator assembly, sans rotor, is studied computationally using three-dimensional (3D) numerical simulations in the commercial computational fluid dynamics (CFD) package Star-CCM+. Examination of the velocity and pressure contours at the central stator plane shows that the maximum induced velocity exceeded the freestream velocity by 65%. However, flow is not sufficiently trapped in the stator assembly, with excess leakage occurring between the stator blades due to adverse pressure gradients and momentum loss from induced vorticity. A parametric study was conducted on the effect of the number of stator blades with simulations conducted with 6, 12, and 24 blades. Reducing the blade number resulted in a reduction in the cohesiveness of the internal swirling flow structure and increased the leakage of flow through the stator. Two unique energy loss mechanisms have been identified with both caused by adverse pressure gradients induced by the stator.

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Strickland, J. H. , Webster, B. T. , and Nguyen, T. , 1979, “ A Vortex Model of the Darrieus Turbine: An Analytical and Experimental Study,” ASME J. Fluids Eng., 101(4), pp. 500–505. [CrossRef]
Gosselin, R. , Dumas, G. , and Boudreau, M. , 2013, “ Parametric Study of H-Darrieus Vertical-Axis Turbines Using uRANS Simulations,” 21st Annual Conference of the CFD Society of Canada (CFDSC), Sherbrooke, QC, Canada, May 6–9, pp. 6–9. http://www.lmfn.ulaval.ca/fileadmin/lmfn/documents/Articles/GosselinDumasBoudreau-CFD2013_reprint.pdf
Ikoma, T. , Masuda, K. , Maeda, H. , and Sasanuma, T. , 2007, “ A Basic Study on Characteristics of Torque and Hydrodynamic Force of Darrieus Water Turbines,” In Conference of the Japan Society of Naval Architects and Ocean Engineers (JASNAOE), Vol. 4, pp. 51–54.
Kotb, M. , and Aldoss, T. , 1991, “ Flow field Around a Partially-Blocked Savonius Rotor,” Appl. Energy, 38(2), pp. 117–132. [CrossRef]
Shaughnessy, B. , and Probert, S. , 1992, “ Partially-Blocked Savonius Rotor,” Appl. Energy, 43(4), pp. 239–249. [CrossRef]
Mohamed, M. , Janiga, G. , Pap, E. , and Thévenin, D. , 2011, “ Optimal Blade Shape of a Modified Savonius Turbine Using an Obstacle Shielding the Returning Blade,” Energy Convers. Manage., 52(1), pp. 236–242. [CrossRef]
Zhang, B. , Song, B. , Mao, Z. , and Tian, W. , 2017, “ A Novel Wake Energy Reuse Method to Optimize the Layout for Savonius-Type Vertical Axis Wind Turbines,” Energy, 121, pp. 341–355. [CrossRef]
Craig, A. E. , Dabiri, J. O. , and Koseff, J. R. , 2016, “ Flow Kinematics in Variable-Height Rotating Cylinder Arrays,” ASME J. Fluids Eng., 138(11), p. 111203. [CrossRef]
Sabzevari, A. , 1977, “ Performance Characteristics of Concentrator-Augmented Savonius Wind Rotors,” Wind Eng., 1(3), pp. 198–206. http://www.jstor.org/stable/43749084
Sivasegaram, S. , 1979, “ Concentration Augmentation of Power in a Savonius-Type Wind Rotor,” Wind Eng., 3(1), pp. 52–61. http://www.jstor.org/stable/43750165
Fukutomi, J. , Shigemitsu, T. , and Daito, H. , 2011, “ Study on Performance and Flow Condition of a Cross-Flow Wind Turbine With a Symmetrical Casing,” ASME J. Fluids Eng., 133(5), p. 051101. [CrossRef]
Sivapalan, S. , and Sivasegaram, S. , 1980, “ Direction-Independent, Concentration-Augmented Slow-Running Wind-Rotors,” Wind Eng., 4(3), pp. 134–141 http://www.jstor.org/stable/43749998.
Sivasegaram, S. , 1986, “ Power Augmentation in Wind Rotors—A Review,” Wind Eng., 10(3), pp. 163–179. http://www.jstor.org/stable/43749280
Altan, B. D. , Atilgan, M. , and Ozdamar, A. , 2008, “ An Experimental Study on Improvement of a Savonius Rotor Performance With Curtaining,” Exp. Therm. Fluid Sci., 32(8), pp. 1673–1678. [CrossRef]
Altan, B. D. , and Atilgan, M. , 2010, “ The Use of a Curtain Design to Increase the Performance Level of a Savonius Wind Rotors,” Renewable Energy, 35(4), pp. 821–829. [CrossRef]
Rowe, J. , 2004, “ Vertical Axis Wind Turbine,” Pacifex Management Inc., King City, ON, Canada, U.S. Patent No. 6,740,989. https://www.google.com/patents/US6740989
Pope, K. , Rodrigues, V. , Doyle, R. , Tsopelas, A. , Gravelsins, R. , Naterer, G. F. , and Tsang, E. , 2010, “ Effects of Stator Vanes on Power Coefficients of a Zephyr Vertical Axis Wind Turbine,” Renewable Energy, 35(5), pp. 1043–1051. [CrossRef]
Pope, K. , Dincer, I. , and Naterer, G. , 2010, “ Energy and Exergy Efficiency Comparison of Horizontal and Vertical Axis Wind Turbines,” Renewable Energy, 35(9), pp. 2102–2113. [CrossRef]
Korprasertsak, N. , Korprasertsak, N. , and Leephakpreeda, T. , 2014, “ CFD Modeling and Design of Wind Boosters for Low Speed Vertical Axis Wind Turbines,” Adv. Mater. Res., 1016, pp. 554–558. [CrossRef]
Korprasertsak, N. , and Leephakpreeda, T. , 2015, “ Optimal Design of Wind Boosters for Low Speed Vertical Axis Wind Turbines,” Appl. Mech. Mater., 798, pp. 195–199. [CrossRef]
Korprasertsak, N. , and Leephakpreeda, T. , 2016, “ Analysis and Optimal Design of Wind Boosters for Vertical Axis Wind Turbines at Low Wind Speed,” J. Wind Eng. Ind. Aerodyn., 159, pp. 9–18. [CrossRef]
Yen, J. T. , 1975, “ Tornado-Type Wind Energy System,” In Energy 10; Annual Intersociety Energy Conversion and Engineering Conference, Newark, DE, Aug. 18–22, pp. 987–994.
Yen, J. T. , 1978, “ Tornado-Type Wind Turbine,” Grumman Aerospace Corporation, Baldwin, NY, U.S. Patent No. 4,070,131. https://www.google.ch/patents/US4070131
Hsu, C. , 1984, “ Tornado Type Wind Turbines,” Iowa State University Research Foundation, Inc., Ames, IA, U.S. Patent No. 4,452,562. http://www.google.com.pg/patents/US4452562
Hsu, C. , and Minachi, A. , 1990, “ Performance Tests of Tornado-Type Wind Turbine Models,” J. Propul. Power, 6(2), pp. 181–185. [CrossRef]
Volk, T. , 1982, “ Performance of Tornado Wind Energy Conversion Systems,” J. Energy, 6(5), pp. 348–350. [CrossRef]
Eriksson, S. , Bernhoff, H. , and Leijon, M. , 2008, “ Evaluation of Different Turbine Concepts for Wind Power,” Renewable Sustainable Energy Rev., 12(5), pp. 1419–1434. [CrossRef]
Rassoulinejad-Mousavi, S. , Jamil, M. , and Layeghi, M. , 2013, “ Experimental Study of a Combined Three Bucket H-Rotor With Savonius Wind Turbine,” World Appl. Sci. J., 28(2), pp. 205–211.
de Farias Neto, S. , Legentilhomme, P. , and Legrand, J. , 1998, “ Finite-Element Simulation of Laminar Swirling Decaying Flow Induced by Means of a Tangential Inlet in an Annulus,” Comput. Methods Appl. Mech. Eng., 165(1–4), pp. 189–213. [CrossRef]
CD-adapco, 2016, “ Star-CCM+,” CD-adapco, Melville, NY.
Sanderse, B. , and Koren, B. , 2009, “ Energy Preservation in the Numerical Calculation of Wind Turbine Wakes,” Euromech Colloquium 508 Wind Turbine Wakes, Madrid, Spain, Oct. 20–22, pp. 16–18. https://www.ecn.nl/publicaties/PdfFetch.aspx?nr=ECN-M--09-145
Shigetomi, A. , Murai, Y. , Tasaka, Y. , and Takeda, Y. , 2011, “ Interactive Flow Field Around Two Savonius Turbines,” Renewable Energy, 36(2), pp. 536–545. [CrossRef]
McLaren, K. , Tullis, S. , and Ziada, S. , 2012, “ Computational Fluid Dynamics Simulation of the Aerodynamics of a High Solidity, Small-Scale Vertical Axis Wind Turbine,” Wind Energy, 15(3), pp. 349–361. [CrossRef]


Grahic Jump Location
Fig. 1

Schematic of the stator model

Grahic Jump Location
Fig. 2

(a) Mesh distribution around the stator assembly and (b) result of the grid sensitivity study between the low (15 ×106 cells), mid (18 ×106 cells), and high (22 ×106 cells) cell count cases

Grahic Jump Location
Fig. 3

Contours of normalized tangential velocity inside the stator at the central plane with velocity vectors overlaid on (d) as representative of the shape of the flow field. Flow is from left to right and is normalized by freestream velocity (V). Re = (a) 278,311, (b) 347,888, (c) 417,466, and (d) 466,171. Reynolds number (Re) is defined based on external diameter of the stator and freestream velocity (V).

Grahic Jump Location
Fig. 4

Bypass rate versus Re

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Fig. 5

CFD time evolution results of the tangential velocity inside the stator at the indicated polar positions for V = 33.5 m/s and Rmax = 105 mm (central plane of stator)

Grahic Jump Location
Fig. 6

Pressure coefficient (Eq. (2)) contours for (a) 20 m/s and (b) 33.5 m/s (mid-height of the stator). Adverse pressure gradients (APG) 1 and 2 are shown in (a) while APG3 is shown in (b).

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Fig. 7

Depiction of the variation of normalized velocity contour (V = 33.5 m/s) with height for 5 cm below the centerline, the centerline, and 5 cm above the centerline (left to right)

Grahic Jump Location
Fig. 8

Depiction of the variation of the vorticity contour (V = 33.5 m/s) with height for 5 cm below the centerline, the centerline, and 5 cm above the centerline (left to right)

Grahic Jump Location
Fig. 9

Pressure coefficient (Eq. (2)) and normalized velocity (V = 33.5 m/s) contours for (a) 6 and (b) 12 blades (mid-height of the stator)

Grahic Jump Location
Fig. 10

Slot concept shown on a single blade



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