Turbulent energy or viscosity

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1

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.

Thanks for your help!

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.

2

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.

3

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(2KTE)/|U|>
And then he defines the boundaries his 1 and 5%.
So will use the Turbulence intensity for my work. THANKS.

4

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.