Wake model + TurbSim


I have been assigned to a project where I have to make TurbSim capable of taking into account a wake model (Jensen, Larsen) in the calculation of the windfiles. To clarify: TurbSim has to generate wind data for the situation behind a user specified turbine at a user specified distance. The implementation is still in a very initial stage where no wake meandering is taken into account and it is assumed that the two turbines are lined up behind each other.

Just as TurbSim has calculated the original velocity field a subroutine is called that calculates the velocity deficient based on several user defined parameters. Another subroutine is called that calculates the added turbulence intensity due to the wake. It is assumed that this added turbulence is isotropic (for now). This calculation is based on user defined parameters as well, but also on the ambient turbulence intensity calculated from the original velocity field.

The velocity deficient is substracted from the velocity field yielding a modified velocity field and then TurbSim starts generating output. During this output generation TurbSim also calculates the turbulence intensity (TI) of the wind.

My questions are related to the turbulence intensity part of TurbSim.

  • As I modify the velocity field the average velocity lowers and the std. dev. stays the same. This results in an increased TI. Should I still add the wake added turbulence to the TI calculated by TurbSim? I understand that this question is not really related to TurbSim itself, but I hope to get an opinion of someone who’s more experienced (I’m just a student).

  • TurbSim calculates the TI in several locations. When writing to the BLADED binary file (sub WrBinBLADED) it calculates the TI for normalization purposes. It uses UHub as the mean velocity.
    In another place it writes the ‘Hub-Height Simulated Turbulence Statistical Summary:’ to the .sum file. Here it uses UBar as the mean velocity. UBar = UHub when the velocity field is not modified. As I modify the field this equality no longer holds. My question is: why are there two different variables used for the calculation of the same parameter? And can I change UHub in UBar without any problems?

Thank you for your help in advance.