TurbSim wind direction change

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Kemal.Kartal
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Location: Germany

TurbSim wind direction change

Postby Kemal.Kartal » Sun Sep 29, 2019 9:24 am

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

Jason.Jonkman
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Re: TurbSim wind direction change

Postby Jason.Jonkman » Mon Sep 30, 2019 6:58 am

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,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Kemal.Kartal
Posts: 13
Joined: Mon Jan 11, 2016 5:01 am
Organization: self
Location: Germany

Re: TurbSim wind direction change

Postby Kemal.Kartal » Wed Oct 02, 2019 3:37 am

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

Jason.Jonkman
Posts: 4280
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: TurbSim wind direction change

Postby Jason.Jonkman » Wed Oct 02, 2019 11:12 am

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
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Kemal.Kartal
Posts: 13
Joined: Mon Jan 11, 2016 5:01 am
Organization: self
Location: Germany

Re: TurbSim wind direction change

Postby Kemal.Kartal » Sat Oct 05, 2019 1:24 am

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.


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