Dear forum

As a part of my master thesis I am currently working on a turbine model which is ultimately going to be used for control design purposes.

I wrote a BEMT code in MATLAB, but after comparison with FAST I noticed that the thrust force was almost the same, while the aerodynamic torque was quite off.

In the FAST simulation I have set all DOF’s to zero except for the rotation, and applied a uniform and constant wind field.

In my code I assume a linear variation in the tangential loads between each node point on the blade, when I carry out integration.

My question is:

How is the aerodynamic torque found in Aerodyn? Is it also assuming linear variation of the tangential loads, or is it held constant for each element under integration?

I wasn’t able to decipher this in the source code and didn’t find the answer to this in the documentation either.

I noticed this section in the AeroDyn_IO.f90 file:

[code] ! integrate force/moments over blades by performing mesh transfer to hub point:

force = 0.0_ReKi

moment = 0.0_ReKi

do k=1,p%NumBlades

call Transfer_Line2_to_Point( y%BladeLoad(k), m%HubLoad, m%B_L_2_H_P(k), ErrStat2, ErrMsg2, u%BladeMotion(k), u%HubMotion )

force = force + m%HubLoad%force( :,1)

moment = moment + m%HubLoad%moment(:,1)

end do

tmp = matmul( u%HubMotion%Orientation(:,:,1), force )

m%AllOuts( RtAeroFxh ) = tmp(1)

m%AllOuts( RtAeroFyh ) = tmp(2)

m%AllOuts( RtAeroFzh ) = tmp(3)

tmp = matmul( u%HubMotion%Orientation(:,:,1), moment )

m%AllOuts( RtAeroMxh ) = tmp(1)

m%AllOuts( RtAeroMyh ) = tmp(2)

m%AllOuts( RtAeroMzh ) = tmp(3)[/code]

Does the function “Transfer_Line2_to_Point” find the force and moment on each blade? or how does it work?

Best regards Stefan