# Turbulent energy or viscosity

A beginners question. Say I have a traditional wind mill in a built environment and I want to understand the extra turbulence at the location of the wings compared to the free field): The full biotoop of the mill - Copy by vreijs | SimScale
I expect that turbulence will add extra forces to the wings.
Which output of CFD is best for this: turbulent energy of turbulent viscosity? And how do I compare the built values with the free field values: subtracts them of divided them)?
If there is some literature/webpage where such a comparison between two different situations (in my case: built en free field) is described, that would also be helpful.

All the best,

Victor

P.S. I was thinking to compare the kinematic energy: determine the standard deviation instead of TKE: sigma(built)=sqrt(2*KTE) en then compare this sigma(built) with the speedmagnitude(built): sigma(built)/speedmagnitude(build))=relative(built).
Do the same for the free field (relative(freefield)) and then compare these two.

The turbulent kinetic energy/turbulence intensity is the way to go. If you have 30 minutes, I’d suggest that you have a look at this video that was recently uploaded on Fluid Mechanics 101’s YouTube channel.

They put out super high quality stuff on various CFD topics.

Thanks Ricardo,
So if using the Fluid Mechanics 101 definition, the urms=sqrt(2KTE/3)
Turbulence intensity=urms/|U
<I was using relative(situation)=sqrt(2
KTE)/|U|>
And then he defines the boundaries his 1 and 5%.
So will use the Turbulence intensity for my work. THANKS.

Just to come back on these boundaries…
If I look at an ABL flow (6.44m/sec @10m and z0=1m) I see at 12.5m heigh;, a speed |U| of 7.2m/sec and a KTE of around 1.6m2/sec2. and this gives an I =sqrt(2KTE)/|U|=sqrt(21.6)/7.2=25%
So his boundaries (1 and 5%) do not really work for an ABL environment.