Spanwise thrust/power along the blade?

Wind & Water Computer-Aided Engineering Software Tools
1

Hello,

In AeroDyn v14, is it possible to output the local thrust or power (preferably the thrust and power coefficients) at each blade node, or do I need to modify the source code to achieve that? If modification is required, any pointers would be very much appreciated.

Update:

AeroDyn v14 can output the following spanwise quantities:

image
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Assuming that all the degrees of freedom are disabled except the rotational speed of the blades, is it correct to compute the local quantities as follows:

Ct_r = CNorm * NumBlades

Cp_r = CTang * r * omega * NumBlades

where omega is rotational speed.

Best regards,

Y.Thiziri

2

Dear @Yoor.Thiziri,

For the element-level PRINT outputs available from AeroDyn v14, CNorm and CTang are the force coefficients normal and tangential to the chordline, so, your equations are not correct. That said, ForceN and ForceT are the element-level forces normal and tagential to the rotor plane, so, to calculate the local thrust coefficient for ith blade element (Ct(i)), you could calculate:

Ct(i) = NumBlades * ForceN / ( AirDens * pi * RNodes(i) * DRNodes(i) * Vinf^2 )

Where Vinf is the disk-averaged free-stream wind speed normal to the rotor disk.

Best regards,

1 Like
3

Dear @Jason.Jonkman ,

Thank you very much for your answer. I have another follow-up question about computing the induction factors (axial and tangential).

I am coupling FAST with a CFD solver so I disabled the wake model (set to None instead of SWIRL/WAKE) which means that Aerodynv14 will report a value of 0 for both AxInd and TanInd.

I have the 3 velocity components (VX/VY/VZ) from the `.wind` file from Aerodyn14 when using the option PRINT WIND. (from this post)

My approach to compute the axial induction at each blade node:

  • Compute the wind speed normal to the rotor plane, U, and compute AxInd = 1 - U/Uinf.
  • To compute the TanInd:
    • Compute the relative speed from the Dynamic pressure output: W = sqrt(2*DynPres/AirDens).
    • Compute the inflow angle: PHI = Alpha + Pitch
    • image
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    • Compute the Tangential relative speed: VT = W * COS(PHI).
    • Compute TanInd from the relation: VT = r*Omega (1 + tanInd).

I appreciate your feedback/corrections.

Best regards,

Y.Thiziri

4

Update:

In AeroDyn 14 there are some debugging line that output VTTotal and VNWind which I believe are the relative tangential speed and the rotor-normal wind component, respectively, i.e.:

image

I can also get the same values for VTTotal and VNWind using the output from RootName.AD.out:

  • Compute the relative speed W = sqrt(2*DynPre/AirDens).
  • Compute the inflow angle: PHI = Alpha + Pitch.
  • Compute VTTotal = W * cos(PHI) and VNWind = W * sin(PHI).
  • Compute axial induction and tangential induction from VTTotal and VNWind.

Best regards,

1 Like