TurbSim wind direction change

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.

Best regards
Kemal

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,

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

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:

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

Hi Jason,

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

Sorry, I have not knowledge to discuss about that.

Ok thank you for your time.

Dear Jason,

I would like to change the wind direction in time in TurbSim. I saw that there is no way but to change “HFlowAng” of the source code INP file. This can be done externally in a loop using MATLAB for example, but how the output files can be merged into a single one to give a single simulation where the wind mean direction changes in time?

Kindest regards

Younes

Dear Younes.

A similar question was asked and answered on our forum before–see: http://forums.nrel.gov/t/stitch-together-turbsim-timeseries/2245/6.

Best regards,

Dear Jason,

I looked at the post you shared and helped me a lot. Thank you!

Kindest regards

Younes