ris-r-1543 - Risø-R-1543(EN) Aerodynamic investigation of...

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Unformatted text preview: Risø-R-1543(EN) Aerodynamic investigation of Winglets on Wind Turbine Blades using CFD Jeppe Johansen and Niels N. Sørensen Risø National Laboratory Roskilde Denmark February 2006 Author: Jeppe Johansen and Niels N. Sørensen Title: Aerodynamic investigation of Winglets on Wind Turbine Blades using CFD Department: Wind Energy Department Risø-R-1543(EN) February 2006 ISSN 0106-2840 ISBN 87-550-3497-7 Contract no.: ENS-33031-0077 Group's own reg. no.: 1110047-01 Sponsorship: Cover : Pages: 17 Tables:2 References:5 Abstract (max. 2000 char.) : The present report describes the numerical investigation of the aerodynamics around a wind turbine blade with a winglet using Computational Fluid Dynamics, CFD. Five winglets were investigated with different twist distribution and camber. Four of them were pointing towards the pressure side (upstream) and one was pointing towards the suction side (downstream). Additionally, a rectangular modification of the original blade tip was designed with the same planform area as the blades with winglets. Results show that adding a winglet to the existing blade increase the force distribution on the outer approx 14 % of the blade leading to increased produced power of around 0.6% to 1.4% for wind speeds larger than 6 m/s. This has to be compared to the increase in thrust of around 1.0% to 1.6%. Pointing the winglet downstream increases the power production even further. The effect of sweep and cant angles is not accounted for in the present investigation and could improve the winglets even more. Risø National Laboratory Information Service Department P.O.Box 49 DK-4000 Roskilde Denmark Telephone +45 46774004 bibl@risoe.dk Fax +45 46774013 www.risoe.dk Contents Introduction 4 1 Winglet design 5 2 Generation of computational mesh 7 3 Results 8 4 Discussions 16 References 16 3 Risø-R-1543(EN) Introduction The following report is made during the EFP 2005 project “Program for Forskning i Anvendt Aeroelasticitet” under the milestone “Avanceret Rotoraerodynamik – herunder tip- og rodaerodynamik”, (Contract number: ENS-33031-0077) which is carried out by the Aeroelastic Design Group, Wind Energy department at Risø National Laboratory and the Fluid Mechanics Section at the Technical University of Denmark. In short, the purpose of adding a winglet to a rotor blade design is to decrease the induced drag from the blade by changing the downwash distribution. The art is then to design a winglet, which carries an aerodynamic load such that the vortex from the winglet spreads out the influence of the tip vortex decreasing the downwash and reduces the induced drag. Or in other words; to design a winglet such that the extra form drag, or profile drag, of the winglet is smaller than the decrease in induced drag such that the total drag is decreased. For further reading the theory and physics of winglets on a sailplane is thoroughly described in ref....
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This note was uploaded on 11/13/2011 for the course AEE 495 taught by Professor O.uzol during the Spring '11 term at Middle East Technical University.

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ris-r-1543 - Risø-R-1543(EN) Aerodynamic investigation of...

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