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Wind Turbines Coordinates System

Global coordinate system (G) / DeepLines global coordinate system

  • origin : global frame origin

  • \(X_G\) : pointing to user required horizontal direction

  • \(Y_G\) : (\(X_G,Y_G,Z_G\)) direct coordinate system
  • \(Z_G\) : pointing vertically upward opposite to gravity

Nacelle coordinate system (N)

  • origin : rigid body reference point, top of the tower

  • (\(X_N, Y_N, Z_N\)),

    • \(X_N\) : defined by the heading of the turbine or by the heading (azimuth) of the fairlead point on which the turbine is connected,

    • \(YN\) : (\(X_N, Y_N, Z_N\)) direct coordinate system

    • \(ZN\) : pointing vertically upward opposite to gravity

Hub coordinate system (H)

  • Origin : rigid body reference point; defined on the Nacelle as Rotor Reference,
  • \(X_H\) : downward (shaft tilt from vertical direction)
  • \(Y_H\) : (\(X_H, Y_H, Z_H\)) direct coordinate system
  • \(Z_H\) : hub rotation, upwind with shaft tilt from horizontal

In the hub local frame, the blades are initially defined as such:

Coned coordinate system (CO)

  • oriented by the blade fairleads of the hub
  • XCO : in the (YH, ZH) plane.
  • YCO : (XCO, YCO, ZCO) direct coordinate system,
  • ZCO : in the blade axis at connection.

The Coned coordinate system is represented below. This frame of reference is fixed with respect to the hub. If the structural twist of the blade is 0 at connection to the hub, then the blade coordinate system (see below) is equivalent to the CO system. Note that in the frame below, the blade is represented in feathered mode, therefore the Blade coordinate system has an angle of about -90 around the Z-axis of the CO system.

Blade coordinate system (B):

  • Origin : mechanical center of the blade (P),

  • XB : direct frame (XB,YB,ZB),

  • YB : direct frame (XB,YB,ZB),

  • ZB : collinear to blades axis, from rotor to blades edge (HAWT).

(XB,YB) are oriented initially as (XCO, YCO) if there is no prebend. If there is a prebend there is a slight difference due to the change in orientation of the blade axis along the blade. Also the blade coordinate system will rotate with the pitch control.

Note that the arc length along the blade is always defined by the length of each section entered as input in the blade panel. When prebend is defined, the mechanical center of the blade P is positioned using IP and OP prebend information. The position is obtained with respect to P defined as the mechanical center of the blade without prebend and in the plane (XB,YB) defined as the Blade coordinate system without prebend. Consistency between initial structural twist and IP/OP prebend should be checked by the user when defining the windturbine.

Aerodynamic Blade coordinate system (AB) :

  • Origin : aerodynamic center,

  • XAB : direct frame (XAB,YAB,ZAB),

  • YAB : collinear to chord, positive from leading edge to trailing edge,

  • ZAB : collinear to blades axis, from rotor to blades edge (HAWT).

Mechanical Blade coordinate system (MB):

  • Origin at the mechanical center of the blade,

  • XMB, YMB, ZMB: derived from the coned coordinate system taking into account the structural twist along the blade axis.