Asymmetric results with variation of vertical angle inflow wind

Wind & Water Computer-Aided Engineering Software Tools
1

Hello everyone,

I am currently studying how variations in wind parameters influence power production. The wind turbine I am using is the WindPACT 3.0 MW. To ensure perpendicular wind flow, I’ve set the shaft tilt and precone angles to 0°.

One parameter I’ve modified is the inflow vertical velocity (via TurbSim). Initially, I didn’t expect significant changes, as I assumed the results would scale with the velocity (cos(β) × velocity) and would be symmetric for ±β.

However, when running the simulation, I observed unexpected results (see attached graph): the negative inflow angle produces a power output closer to the base state compared to the positive angle. -1° angle even produces more power than the base state !

Could this be due to differences in wind potential energy or an asymmetry in the blade geometry? Or is there another explanation?

DeltaP_vertical_angle
DeltaP_vertical_angle2780×1488 87.7 KB

On the graph, I’ve plotted ΔP = (Power with modified inflow) - (Power with base state), where the base state corresponds to steady, parallel wind.

I’d greatly appreciate any insights or suggestions!

Thanks in advance,
Alice Baruzier

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Dear @Alice.Baruzier,

Can you clarify what you mean by beta? Is this the vertical inflow angle, i.e., arctan(W/U)?\

Also, are you using OpenFAST (which version) and have you enabled any structural degrees of freedom (DOFs)? If you’ve enabled the tower-bending DOFs, the tower deflection would lead to an effective shaft tilt angle even if you’ve set ShftTilt = 0, which could explain the asymmetry in your results.

Best regards,

3

Hello,

Thank you for your response, and I apologize for the lack of clarity.

To clarify, by “beta,” I am referring to the VFlowAng parameter in TurbSim, which corresponds to the “Vertical mean flow (uptilt) angle [degrees].”

I am using OpenFAST version 13.2.0 and TurbSim version 3.5.3.

As you suggested, I tested with all structural DOFs set to false, and you are correct — this had a significant impact on the asymmetry and the overall power generation.

Thanks again for your insights!

Best regards,
Alice

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