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The Effect of Wind Turbine Rotor Deflection on Its Aerodynamic Performance Using Actuator Disc Model

Jalali, Ramin | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48301 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Darbandi, Masoud
  7. Abstract:
  8. An aerodynamical model for studying asymmetric and three-dimensional flow fields about wind turbine rotors is presented. The developed algorithm combines a asymmetric and three-dimensional Navier-Stokes solver with a so-called actuator disc technique in which the loading is distributed along lines representing the blade forces. The loading is determined iteratively using a bladeelement approach and tabulated airfoil data. Computations are carried out for a 5MW NREL wind turbine equipped with three blades. The computed power production is found to be in good agreement with measurements. The computations give detailed information about basic features of wind turbine wakes, including distributions of interference factors and vortex structures. The model serves in particular to analyze and verify the validity of the basic assumptions employed in the simple engineering models. The influence of coning a wind turbine rotor is analysed numerically using the blade element momentum (BEM) method and an actuator disc model combined with the Navier–Stokes equations. The two models are compared and short comings of the BEM model are discussed. In accordance with theoretical predictions and investigations by Madsen and Rasmussen (European Wind Energy Conference, Nice, 1999; 138–141), the computations demonstrate that the power coefficient based on the projected area of the actuator disc is invariant to coning. The induced velocities, however, are no longer constant, but vary as a function of spanwise position. Next, the flow past the 5MW NREL wind turbine is computed with and without coning. The most important findings from this study are that, although the power is reduced when the rotor is coned, the power coefficient based on the projected area is only slightly changed. The computations show that upstream coning results in a 2%–3% point lower power production than the corresponding downstream coning of the rotor
  9. Keywords:
  10. Megawatt Wind Turbine ; Computational Fluid Dynamics (CFD) ; Blade Element Momentum Theory ; Actuator Disk Method ; Coned Angle

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