Effect of swept design on the normal inflow velocity of the blade.

[winder365]

Dear @jjonkman,

I modified the BlSwpAC in the "IEA-15-240-RWT_AeroDyn15_blade.dat" file to investigate the swept design on the performance of the IEA-15 MW wind turbine. The modified "IEA-15-240-RWT_AeroDyn15_blade.dat" file is shown as following, the swept distance (namely the d_tip in the figure) is about 10 m:

Then operation condition of the wind turbine is constant 10.59 m/s&7.55 rpm, without servo control. As can be seen in the following figure, the Vx of the swept blade is different from that of the original blade (namely the blade without swept design).

I am confused that why the the blade swept design has so significant effect on the Vx (namely the Local axial velocity in OutListParameters.xlsx) at each node.

Best wishes,

[jjonkman]

Dear @winder365,

Which version of OpenFAST are you using?

I know that Vx is one of the AeroDyn nodal outputs that we plan to deprecate, because the coordinate system is ill defined and implementation specific, meaning that its orientation depends on which aerodynamic options are enabled. I would instead output the velocities in well of the well-defined coordinate systems (inertial, polar, local polar, airfoil), which should then help you better understand the influence of sweep on the output. See the documentation of AeroDyn's coordinate systems for more information: https://openfast.readthedocs.io/en/main/source/user/aerodyn/coordsys.html#coordinate-systems.

Best regards,