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Christian Bak - One of the best experts on this subject based on the ideXlab platform.
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Development of the Risø wind turbine Airfoils
Wind Energy, 2004Co-Authors: Peter Fuglsang, Christian BakAbstract:This paper presents the wind turbine airfoil development at Ris�.\nThe design method is\n\ndescribed together with our target characteristics for wind turbine\nAirfoils. The use of the\n\nCFD code Ellipsys2D for prediction of final target characteristics\nis described together with\n\nthe VELUX wind tunnel testing setup. Three airfoil families were developed;\nRis�-A1, Ris�-P\n\nand Ris�-B1. The Ris�-A1 airfoil family was developed for rotors of\n600 kW and larger. Wind\n\ntunnel testing and field testing showed that this airfoil family is\nwell suited for stall and\n\nactive stall control. However, sensitivity to roughness was higher\nthan expected. Field tests\n\nof a 600 kW active stall wind turbine showed an estimated reduction\nin blade fatigue\n\nloading of up to 15% at the same annual energy yield and at the same\ntime reduced blade\n\nweight and blade solidity. The Ris�-P Airfoils were developed to replace\nthe Ris�-A1 Airfoils\n\nfor use on pitch controlled wind turbines. Improved design objectives\nshould reduce the sen-sitivity to roughness, but measurements are\nnot yet available. The Ris�-B1 airfoil family was\n\ndeveloped for variable speed operation with pitch control of large\nmegawatt sized rotors.\n\nWind tunnel testing verified the high maximum lift for these Airfoils,\nand the Airfoils were\n\nfound to be very insensitive to leading edge roughness. Performance\nwith vortex genera-tors and Gurney flaps in combination was found\nto be attractive for the blade root part.\n\nField testing of a 1�5 MW rotor is in progress. Copyright � 2004 John\nWiley & So
Anya R. Jones - One of the best experts on this subject based on the ideXlab platform.
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Reynolds Number Effects on Airfoils in Reverse Flow
53rd AIAA Aerospace Sciences Meeting, 2015Co-Authors: Andrew H. Lind, Luke R. Smith, Joseph Milluzzo, Anya R. JonesAbstract:This work is aimed at providing an improved understanding of the impact of the radial Reynolds number distribution that exists in the reverse flow region of a helicopter operating at high advance ratios. Time-averaged sectional airloads and flow fields were measured experimentally for four Airfoils in forward and reverse flow at Reynolds numbers between 3.3× 10 and 1.0× 10. Two Airfoils with a sharp geometric trailing edge (NACA 0012 and NACA 0024) and two Airfoils with a blunt geometric trailing edge (a 24 % thick elliptical airfoil, and a 26 % thick cambered ellipse airfoil) were tested. This work shows that the airloads for a NACA 0012 in reverse flow (a “thin” airfoil with a sharp aerodynamic leading edge) are insensitive to Reynolds number due to early flow separation. The airloads of thicker Airfoils are found to be more sensitive to Reynolds number. In reverse flow, a NACA 0024 airfoil exhibits a decrease in the magnitude of the airloads with increasing Reynolds number for −3 ≤ −αrev ≤ 15deg. The lift curve of an elliptical airfoil becomes more linear with increasing Reynolds number. The character of the lift curve for the cambered ellipse airfoil in both forward and reverse flow changes drastically for Re ≥ 3.3 × 10. This includes a large shift in the zero-lift angle of attack. These results give insight to the design of high-speed helicopter rotor blades by examining the sensitivity of airloads to the range of Reynolds numbers encountered in the reverse flow region.
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Time-Averaged Aerodynamics of Sharp and Blunt Trailing-Edge Static Airfoils in Reverse Flow
AIAA Journal, 2014Co-Authors: Andrew H. Lind, Jonathan N. Lefebvre, Anya R. JonesAbstract:Two-dimensional wind-tunnel experiments have been conducted on three Airfoils held at static angles of attack through 360 deg at a Reynolds number of Re=1.1×105 to evaluate the influence of trailing-edge shape on time-averaged force and flowfield measurements. The present study focuses on airfoil performance in reverse flow to advance the understanding of this flow regime for high-speed helicopter applications. It is shown that the drag of a NACA 0012 airfoil in reverse flow is more than twice as large compared to forward flow due to early flow separation, similar to a flat plate. Two blunt trailing-edge Airfoils are considered in this work: an elliptical airfoil and the DBLN-526. Both Airfoils exhibit a rapid increase in lift at low angles of attack in both forward and reverse flows. The drag of the elliptical airfoil in reverse flow is significantly lower than the NACA 0012 for 5
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time averaged aerodynamics of sharp and blunt trailing edge static Airfoils in reverse flow
AIAA Journal, 2014Co-Authors: Andrew Lind, Jonathan N. Lefebvre, Anya R. JonesAbstract:Two-dimensional wind-tunnel experiments have been conducted on three Airfoils held at static angles of attack through 360 deg at a Reynolds number of Re=1.1×105 to evaluate the influence of trailing-edge shape on time-averaged force and flowfield measurements. The present study focuses on airfoil performance in reverse flow to advance the understanding of this flow regime for high-speed helicopter applications. It is shown that the drag of a NACA 0012 airfoil in reverse flow is more than twice as large compared to forward flow due to early flow separation, similar to a flat plate. Two blunt trailing-edge Airfoils are considered in this work: an elliptical airfoil and the DBLN-526. Both Airfoils exhibit a rapid increase in lift at low angles of attack in both forward and reverse flows. The drag of the elliptical airfoil in reverse flow is significantly lower than the NACA 0012 for 5<αrev<17 deg. Lift was calculated via a circulation box method applied to time-averaged flowfield measurements and compared t...
Peter Fuglsang - One of the best experts on this subject based on the ideXlab platform.
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Development of the Risø wind turbine Airfoils
Wind Energy, 2004Co-Authors: Peter Fuglsang, Christian BakAbstract:This paper presents the wind turbine airfoil development at Ris�.\nThe design method is\n\ndescribed together with our target characteristics for wind turbine\nAirfoils. The use of the\n\nCFD code Ellipsys2D for prediction of final target characteristics\nis described together with\n\nthe VELUX wind tunnel testing setup. Three airfoil families were developed;\nRis�-A1, Ris�-P\n\nand Ris�-B1. The Ris�-A1 airfoil family was developed for rotors of\n600 kW and larger. Wind\n\ntunnel testing and field testing showed that this airfoil family is\nwell suited for stall and\n\nactive stall control. However, sensitivity to roughness was higher\nthan expected. Field tests\n\nof a 600 kW active stall wind turbine showed an estimated reduction\nin blade fatigue\n\nloading of up to 15% at the same annual energy yield and at the same\ntime reduced blade\n\nweight and blade solidity. The Ris�-P Airfoils were developed to replace\nthe Ris�-A1 Airfoils\n\nfor use on pitch controlled wind turbines. Improved design objectives\nshould reduce the sen-sitivity to roughness, but measurements are\nnot yet available. The Ris�-B1 airfoil family was\n\ndeveloped for variable speed operation with pitch control of large\nmegawatt sized rotors.\n\nWind tunnel testing verified the high maximum lift for these Airfoils,\nand the Airfoils were\n\nfound to be very insensitive to leading edge roughness. Performance\nwith vortex genera-tors and Gurney flaps in combination was found\nto be attractive for the blade root part.\n\nField testing of a 1�5 MW rotor is in progress. Copyright � 2004 John\nWiley & So
J J R Williams - One of the best experts on this subject based on the ideXlab platform.
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aerodynamic improvements of wind turbine airfoil geometries with the prescribed surface curvature distribution blade design circle method
Journal of Engineering for Gas Turbines and Power-transactions of The Asme, 2012Co-Authors: Theodosios Korakianitis, Mohammad Amin Rezaienia, I A Hamakhan, E J Avital, J J R WilliamsAbstract:The prescribed surface curvature distribution blade design (CIRCLE) method can be used for the design of two-dimensional (2D) and three-dimensional (3D) turbomachinery blade rows with continuous curvature and slope of curvature from leading edge (LE) stagnation point to trailing edge (TE) stagnation point and back to the LE stagnation point. This feature results in smooth surface pressure distribution Airfoils with inherently good aerodynamic performance. In this paper the CIRCLE blade design method is modified for the design of 2D isolated Airfoils. As an illustration of the capabilities of the method, it is applied to the redesign of two representative Airfoils used in wind turbine blades: the Eppler 387 airfoil and the NREL S814 airfoil. Computational fluid dynamic analysis is used to investigate the design point and off-design performance of the original and modified Airfoils, and compare with experiments on the original ones. The computed aerodynamic advantages of the modified Airfoils are discussed. The surface pressure distributions, drag coefficients, and lift-to-drag coefficients of the original and redesigned Airfoils are examined. It is concluded that the method can be used for the design of wind turbine blade geometries of superior aerodynamic performance. [DOI: 10.1115/1.4005969]
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aerodynamic improvements of wind turbine airfoil geometries with the prescribed surface curvature distribution blade design circle method
Volume 1: Aircraft Engine; Ceramics; Coal Biomass and Alternative Fuels; Wind Turbine Technology, 2011Co-Authors: Theodosios Korakianitis, Mohammad Amin Rezaienia, I A Hamakhan, E J Avital, J J R WilliamsAbstract:The presc ri bed sur face c urvature distribution bl ade de sign (CIRCLE) method can be used for the design of two-dimensional (2D) and three-dimensional (3D) turbomachinery blade rows with continuous curvature and slope of curvature from leading edge (LE) stagnation point to trailing edge (TE) stagnation point and back to the LE stagnation point. This feature results in smooth surface pressure distribution Airfoils with inherently good aerodynamic performance. In this paper the CIRCLE blade design method is modified for the design of 2D isolated Airfoils. As an illustration of the capabilities of the method, it is applied to the redesign of two representative Airfoils used in wind turbine blades: the Eppler 387 airfoil; and the NREL S814 airfoil. Computational fluid dynamic analysis is used to investigate the design point and off-design performance of the original and modified Airfoils, and compare with experiments on the original ones. The computed aerodynamic advantages of the modified Airfoils are discussed. The surface pressure distributions, drag coefficients, and lift-to-drag coefficients of the original and redesigned Airfoils are examined. It is concluded that the method can be used for the design of wind turbine blade geometries of superior aerodynamic performance.Copyright © 2011 by ASME
Severin Kempf - One of the best experts on this subject based on the ideXlab platform.
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Numerical Investigation of Tandem Airfoils for Subsonic Axial-Flow Compressor Blades
Journal of Turbomachinery-transactions of The Asme, 2009Co-Authors: Jonathan Mcglumphy, Wing-fai Ng, Steven R. Wellborn, Severin KempfAbstract:The tandem airfoil has potential to do more work as a compressor blade than a single airfoil without incurring significantly higher losses. Although tandem blades are sometimes employed as stators, they have not been used in any known commercial rotors. While the long-term goal for this program is development of a commercially viable tandem rotor, this paper discusses tandem Airfoils in subsonic, shock-free rectilinear cascade flow. Existing literature data on tandem Airfoils in rectilinear cascades have been compiled and presented in a Lieblein loss versus loading correlation. Large scatter in the data gave motivation to conduct an extensive 2D computational fluid dynamics (CFD) study evaluating the overall performance as a function of the relative positions of the forward and aft Airfoils. CFD results were consistent with trends in the open literature, both of which indicate that a properly designed tandem airfoil can outperform a comparable single airfoil on and off design. The general agreement of the CFD and literature data serves as a validation for the computational approach.
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numerical investigation of tandem Airfoils for subsonic axial flow compressor blades
ASME 2007 International Mechanical Engineering Congress and Exposition, 2007Co-Authors: Jonathan Mcglumphy, Steven R. Wellborn, Severin KempfAbstract:The tandem airfoil has potential to do more work as a compressor blade than a single airfoil without incurring significantly higher losses. Although tandem blades are sometimes employed as stators, they have not been used in any known commercial rotors. While the long-term goal for this program is development of a commercially viable tandem rotor, this paper discusses tandem Airfoils in subsonic, shock-free rectilinear cascade flow. Existing literature data on tandem Airfoils in rectilinear cascades have been compiled and presented in a Lieblein loss versus loading correlation. Large scatter in the data gave motivation to conduct an extensive 2-D CFD study evaluating the overall performance as a function of the relative positions of the forward and aft Airfoils. CFD results were consistent with trends in the open literature, both of which indicate that a properly designed tandem airfoil can outperform a comparable single airfoil on- and off-design. The general agreement of the CFD and literature data serves as a validation for the computational approach.Copyright © 2007 by ASME
