GC: n
CT: Yaw dynamics have been investigated by a number of researchers. The most comprehensive work was done by Swift (Swift, 1981 3. He developed a model which was used as the starting point for the work reported herein, He used bladeelernent/mornentum aerodynamics and was the first wind turbine analyst to use the skewed wake effects as developed for helicopter analysis (Coleman, Feingold et al., 1945; Gaonkar and Peters, 1986; Rtt md Peters, 19811. As will be shown later, these effects are crucial to correct estimation of aerodynamic yaw moments. He also considered induction lag, or the time delay between a change in thrust loading of a rotor and the induced velocity field of that rotor. His model uses linear aerodynamics and idealized twist and chord distributions to simplify the aerodynamics analysis. de Vries (de Vries, 19851 discussed the inability of simple blade-element/momentum theory to adequately predict aerodynamic yaw moments on a rotor. He showed that a simple adjustment to the induced velocity field exhibited the correct qualitative influence on the moments. Swift, mentioned above, however was first to show a quantitative method based in physical principles for performing the adjustment.
Chaiyapinunt and Wilson (Chiyapinma and Wilson, 1983) showed that blade stiffness influences yaw motion by affecting the phase angle between an aerodynamic input such as tower shadow and the structural response. They showed that tower shadow will cause a steady yaw tracking error when rotor blades are not infinitely stiff. They also stated that blade element/momentum methods predict very small aerodynamic yaw, moments on a rotor unless the rotor has preconing.
S: UOU – http://www.nrel.gov/docs/legosti/old/4822.pdf, p. 2 (last access: 3 November 2014)
N: 1. Origin unknown. First Known Use: 1546.
Movement of an airplane, ship, etc., to the left or right; especially: unwanted left or right movement.
The action of yawing; especially: a side to side movement.
The extent of the movement in yawing.
From the verb to yaw: “to fall away from the line of a course,” 1580s (as a noun 1540s), perhaps ultimately from Old Norse jaga, Old Danish jæge “to drive, chase,” from Middle Low German jagen (see yacht).
2. The rotation of the HAWT (horizontal axis wind turbine) about its vertical axis to align it with the wind.
S: 1. MW – http://www.merriam-webster.com/dictionary/yaw (last access: 21 December 2014); OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=yaw&searchmode=none (last access: 21 December 2014). 2. TERMIUMPLUS.
SYN:
S:
CR: wind energy, [wind turbine].
