# Questions regarding .sum statistics

Greetings!

I’m a student at NTNU in Norway, and I’m currently working on my masters thesis about aeroelastic software and Turbsim.

A part of my task is to perform a parameter study on Turbsim. I’m now inspecting the .sum files of simulations with different amount of gridpoints e.g. 10x10, 20x20 and so on. I’m only using IEC kaimal parameters.
I have a few questions regarding the statistics in the .sum file:

statistics

• What would be the most important statistic for mechanical engineers (I’m studying computer science primarily)

U*

• As far as i know, the friction velocity is used to describe shear-related motion in moving fluids. Different amount of gridpoints gave me very different output for friction velocity (or u_star) ranging from 0.1 to 0.6. What does this mean? Shouldn’t this statistic be the same irregardless of the different grid resolutions?

literature

• Do you know any literature on the statistical approach to turbulence apart from Burton, Hau and Hansen’s books on the subject?
I’m having some trouble understanding the turbulence models like Kaimal and Mann.

In case some guys want to take a look at my runtime analysis, I’m adding a plot which shows runtime as function of gridpoints (square grid) with IEC Kaimal standard input.
As far as I recall, Dr Jonkman’s analysis only covered lower grid resolutions.

P.S. I’ve read the manual and also searched the forum.

Also I would like to thank you guys at NWTC for making this software available for everyone. It’s really useful for students like me

Thanks for the questions and plot. It’s interesting to see how the performance scales. Often times the number of gridpoints is not something we can choose: typically you want to have your grid fine enough that the grid resolution is similar to the turbine’s chord length, so that you correctly capture the turbine response.