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TurbSim wind direction change

Posted: Sun Sep 29, 2019 9:24 am
by Kemal.Kartal
Hallo,

is there any option to generate windfields or use windfields with direction change? I find the TurbSim input parameter "HFlowAng". But this value is constant for the whole simulation. Below you see the option in Bladed.

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Best regards
Kemal

Re: TurbSim wind direction change

Posted: Mon Sep 30, 2019 6:58 am
by Jason.Jonkman
Dear Kemal,

You can set the fixed wind direction in either TurbSim (HFlowAng) or the InflowWind module of FAST / OpenFAST (PropagationDir), but the latter is preferred because the wind will propagate along the wind direction specified in InflowWind (PropagationDir) regardless of the setting of HFlowAng in TurbSim.

Without changing the source code, there is no way to prescribe a time-varying wind direction of the TurbSim wind field in FAST / OpenFAST. It is standard practice to run many FAST / OpenFAST simulations (each with different wind speed, turbulence intensities, etc.) at fixed wind directions. The design standards (e.g., IEC 61400-1) also specify discrete gust and direction-change events, but these simulations do not involve full-field turbulence.

Best regards,

Re: TurbSim wind direction change

Posted: Wed Oct 02, 2019 3:37 am
by Kemal.Kartal
Thank you very much for your feedback. For the load case 1.2, the IEC does not state that the yaw error should be +-8 degree. It only says to include one if ... The GL wants a yaw error of +-8 degrees. But it does not say that the direction should be constant +-8 degrees, only in average. This means that the simulant can also implement a wind change to reach 8 degrees in average. For example from -10° to -6°. Some simulations shows, that constant wind directions from the side generating higher loads then winds from the side with a direction change.

Do you think, that this parameter will be included?

Best regards
Kemal

Re: TurbSim wind direction change

Posted: Wed Oct 02, 2019 11:12 am
by Jason.Jonkman
Dear Kemal,

The wind direction (HFlowAng in TurbSim or PropagationDir in InflowWind) are the mean wind direction during the simulation. The instantaneous wind direction would change based on the turbulence.

I would question how accurately the numerical simulation can model a slow wind direction combined with turbulence because of how the Taylor's frozen turbulence assumption is used to transform turbulent wind on a 2D plane (from TurbSim) into a 3D volume in FAST / OpenFAST.

I'm not sure I understand your question:
Do you think, that this parameter will be included?
If you are asking whether we intend to introduce this feature in OpenFAST, the answer is no because of the Taylor's frozen turbulence approach.

Best regards

Re: TurbSim wind direction change

Posted: Sat Oct 05, 2019 1:24 am
by Kemal.Kartal
Hi Jason,

The wind direction (HFlowAng in TurbSim or PropagationDir in InflowWind) are the mean wind direction during the simulation. The instantaneous wind direction would change based on the turbulence.

You are right, but with the asked parameter you can choose the range.

I would question how accurately the numerical simulation can model a slow wind direction combined with turbulence because of how the Taylor's frozen turbulence assumption is used to transform turbulent wind on a 2D plane (from TurbSim) into a 3D volume in FAST / OpenFAST.

Sorry, I have not knowledge to discuss about that.

If you are asking whether we intend to introduce this feature in OpenFAST, the answer is no because of the Taylor's frozen turbulence approach.

Ok thank you for your time.