[Martin1]

Dear Friends,

I am using a Smagorinsky LES model in my simulations but I can't make a contour plot of the turbulence intensity since that option does not exist in the contours list. I have to make a user defined function but don't know how the turbulent intensity is defined in fluent for this turbulent model.

I have used the equation TI = u'/u

where u'=( 1/3 * (uv'^2 + uw'^2 +vx'^2) )

where the terms uv', uw' etc are the resolved reynolds stress components obtained under unsteady statistics. But this does not give reasonable contour plots.

Can anyone please help me to define the turbulent intensity.

[Martin1]

No one can help?

[susovanpal]

Hello martin1. I am also having the same problem. Have you got any solution for this?

[swpnl9282@gmail.com]

Hello all,
I'm doing simulation of heat exchanger.
Shell side fluid is water and tube side fluid is hot gas.
So how to capture the properties of gad only in UDF.
If anyone had idea about it, please let me know as early as possible

Sent from my Moto G (4) using CFD Online Forum mobile app

[LuckyTran]

Originally Posted by susovanpal

Hello martin1. I am also having the same problem. Have you got any solution for this?

There is a resolved part of the TKE based on the fluctuation of the resolved part (the filtered) velocities. The resolved part of k, say k_resolved = 0.5(u'^2+v'^2+w'^2).

Now you need to get the turbulent kinetic energy of the subgrid scale. This is the tricky part. I forget the formula, it's hiding somewhere in the Fluent manual and Pope's book, but it involves the subgrid scale filter length, and subgridscale viscosity. I could dig it up out of my code later.

However, to get the average subgrid scale kinetic energy you still need to average it. Which means you need to create a custom field function or UDF. Custom field functions don't run in parallel pre-v18, so if you're using anything before v18 it needs a UDF.