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Validating power and thrust coefficient

Hi all,

I am currently working my way into the simulation of a VAWT. the calculations are stable and I enjoy the user-friendly operation. (Thanks to the developers!)
The power coefficient cp = 0.39, which is displayed in the “Global Visualisations” (picture 1), seemed a bit too high to me, so I took a look at the results of the simulation. In the channel “Aero. Power [kW]”, I calculated an average value over a converged period and compared it with the power of the wind. I got a cp = 0.34.
I did the same with the thrust coefficient. The “Global Visualisations” give ct = 0.98. The mean value of the sum of channel “X_l For. TWR pos 0.000 [N]” and “Y_l For. TWR pos 0.000 [N]” calculates the thrust at the base of the tower. If I compare this with the thrust of the wind, I only get ct = 0.05.

Perhaps I look at the wrong chanels for the thrust?

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I could answer the question regrading the thrust on my own: I used guy ropes and forgot them. That’s why there were practically no forces at the tower bottom.

Hi Josua,

whats being shown in the “overview” next to the visualization are the current values from the “Aeroynamic Time Graph”. Aerodynamic Power, Aerodynamic Thrust, Power Coefficient and Thrust Coefficient for VAWT’s are already averaged over the last full revolution. In the graphs you also find the “Momentary” non-averaged values. The conversion from power to Cp is done based on windspeed and projected area of the rotor – it should be correct.



Hi David,

thank you for your answer. I really appreciate your work!

I still have concerns, but will first acquaint myself further.

BR, Josua

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