Modeling Low Level Jet Profile with High Wind Speed in TurbSim

Discuss the effects of turbulence on wind turbines and its simulation.

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Amber.Kapoor
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Joined: Mon May 14, 2018 10:15 am
Organization: University of Massachusetts
Location: Massachusetts

Modeling Low Level Jet Profile with High Wind Speed in TurbSim

Postby Amber.Kapoor » Tue May 15, 2018 2:56 pm

We are trying to replicate wind data in TurbSim that was generated with a large-eddy simulation. Some of the LES data follow a low level jet wind profile so we've used the GP_LLJ spectral model and JET wind profile. The specific LES profile we are trying to replicate is below.
LES_windprofile_x10.jpg
LES_windprofile_x10.jpg (20.75 KiB) Viewed 3883 times

If we run TurbSim with a URef of 40 mps or less and default values for the Non-IEC Meteorological Boundary Conditions and Spatial Coherence Parameters, we get a reasonable profile.
profile_u35_defaults.jpg
profile_u35_defaults.jpg (24.01 KiB) Viewed 3883 times

But we need the mean wind speed to be above 70 mps (72 mps for the LES case mentioned above). If we run TurbSim with the same default parameters mentioned above but a URef of 72, we get a strange profile at the top and bottom of the grid.
windprofile_x10_U72_defaults.jpg
windprofile_x10_U72_defaults.jpg (34.58 KiB) Viewed 3883 times

It looks like the middle of the profile is following the LLJ profile but the top and bottom are following a log profile or something similar. I tried adjusting the RICH NO and the UStar values but those didn't impact the profile much.
Are there any suggested changes I could make to the input file that will help? Is it possible to model the LLJ profile with higher mean wind speeds in TurbSim?
Thank you,
Amber

Jason.Jonkman
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Re: Modeling Low Level Jet Profile with High Wind Speed in TurbSim

Postby Jason.Jonkman » Wed May 16, 2018 7:37 am

Dear Amber,

I'm not sure I know enough myself about the GP_LLJ model to know if it is possible to get the wind-speed profile you want through changes to the settings in the input file. The GP_LLJ model is really a site-specific model.

However, one option you have is to specify your own user-defined wind-speed profile. TurbSim v2.0 (available here: https://nwtc.nrel.gov/alphas) makes it easy for users to specify their own user-defined wind-speed profile, as well as user-defined spectra, coherence, Reynolds' stresses, etc. I suggest perusing the TurbSim v2.0 documentation to see what new functionality is available.

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


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