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Cfd00d December 4, 2013 20:32

Turbulent kinetic Energy

I have a 3x3x3 mesh grid (chosen for simplicity) that I am using to analyze turbulent velocities. The turbulence is isotropic.

I have u-velocity measurements (fluctuations) made on the grid that were taken at some time, t. I also have v and w velocities that are the same size.

I would like to find the turbulent kinetic energy by using the equation \frac{1}{2} (u ^{2}_{ii})

What I am stuck on is understanding how to apply this equation to my data.

In example, if I wanted to plot TKE vs. t, I should only get a single point, right?

How do I boil down this data to get the single point?

Any help is appreciated.

pbachant December 5, 2013 11:45

You could pick a point and look at the turbulence kinetic energy over time. You could also average over the volume.

If your data is a sequence of 3D velocity fluctuation arrays, you can create a new k array by
\frac{1}{2}\left( u'^2 + v'^2 + w'^2 \right),
or squaring each element of the velocity fluctuation arrays and adding the arrays for each component to each other. If you have arrays of the total velocity, you will need to compute the time average for each point and subtract.

Cfd00d December 5, 2013 16:30

Thank you for your reply pbachant

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