How does turbsim generate turbulent winds that vary in height

[cjking1226]

If I want to create a turbulent wind with wind direction changing along the height, for example, the wind direction changes by 0.05deg for every 1m higher, can this be set on turbsim or modify the Bts file

[jjonkman]

Dear @cjking1226,

You can define your own wind profile in TurbSim, including shear and veer, by selecting WindProfileType = "USR" and specifying the profile in ProfileFile. See the UsrShear.inp example in the TurbSim v2 CertTest for an example: https://www.nrel.gov/docs/libraries/wind-docs/turbsim_v2-00-07a-bjj-exe.exe?sfvrsn=aa667e46_1&download=true.

Best regards,

[cjking1226]

Dear @cjking1226,

You can define your own wind profile in TurbSim, including shear and veer, by selecting WindProfileType = "USR" and specifying the profile in ProfileFile. See the UsrShear.inp example in the TurbSim v2 CertTest for an example: https://www.nrel.gov/docs/libraries/wind-docs/turbsim_v2-00-07a-bjj-exe.exe?sfvrsn=aa667e46_1&download=true.

Best regards,

Thank you very much for receiving your reply. What should I do if I want to implement turbulent wind input with these three conditions in openfast

[jjonkman]

Dear @cjking1226,

The mean wind speed and wind direction with height can be specified directly in the ProfileFile I referred to in my previous post.

TurbSim does not permit you to directly specify the turbulence intensity as a function of height (without changing the source code). Rather, the standard deviation of turbulence can be specified, but is assumed to be uniform across the inflow plane. With mean wind speed increasing with height, this will naturally lead to a turbulence intensity (TI = std(U)/mean(U)) that decreases with height as you show.

Best regards,

[cjking1226]

Thank you very much for your help. On the basis of you, I have simulated three inflow conditions. Please see the three figures. I used your method for speed and direction, and then input the Standard Deviation and Length Scale required in the table of USRVKM turbulence model according to the empirical formula, such as: k = 0.41;
L0 = 42; % Reference length scale, L = k * heights./ (1 + k * heights/L0); sigma = turb_intensities .* wind_speeds / 100; However, according to this formula, I directly input turbsim, and the calculated TI has a certain deviation. Then I divided the target number of each layer by my existing value, took the square root of this ratio, and multiplied by my previous standard deviation, and finally got the target value. Do you think this method is right

[jjonkman]

Dear @cjking1226,

Certainly your wind shear and direction look correct.

That said, I'm not familiar with the equation you are using in the USRVKM spectra model to calculate length scale based on height and I'm not following how you are updating the standard deviation.

Best regards,