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LES Anything concerning Large Eddy Simulation
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Useful LES tools in Fluent - Part 1

Posted August 2, 2013 at 04:15 by sbaffini (NuTBox)
Updated December 21, 2016 at 09:09 by sbaffini

Here i collect some very basic tools i used when performing basic LES computations in Fluent.

1) Custom field function for the Q criterion (q_crit.txt, to be renamed in .scm). Some Fluent versions (12, 13 and maybe 14) only have a "Normalized Q criterion" scalar, while previous ones simply don't have it at all. This custom field function is what i used in those dark days.

2) Several initialization routines (init*.c and scalefield.c) fully described in the files...
Attached Files
File Type: txt q_crit.txt (2.3 KB, 2224 views)
File Type: c initialize_chan.c (1.7 KB, 674 views)
File Type: c initialize_pipe.c (1.6 KB, 559 views)
File Type: c initTGV.c (1.3 KB, 488 views)
File Type: c scalefield.c (787 Bytes, 564 views)
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Old

Q-criterion isosurfaces in MATLAB

Posted July 1, 2013 at 11:33 by sbaffini (NuTBox)
Updated December 21, 2016 at 09:09 by sbaffini

Let us suppose you have the following matrices:

x(nx,ny,nz): x coordinates of your grid

y(nx,ny,nz): y coordinates of your grid

z(nx,ny,nz): z coordinates of your grid

dudx(nx,ny,nz): x-wise derivative of x-wise velocity component

dudy(nx,ny,nz): y-wise derivative of x-wise velocity component
.
.
.
dwdz(nx,ny,nz): z-wise derivative of z-wise velocity component

This is, more or less, how i would...
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Old

LES in Fluent: channel flow test case

Posted July 1, 2013 at 11:12 by sbaffini (NuTBox)
Updated December 21, 2016 at 09:10 by sbaffini

A paper produced for a national conference. Some basic details of the LES in Fluent are covered, together with the main setup:

http://www.lamc.ing.unibo.it/aimeta2.../MEM-273-0.pdf
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Old

Lambda-2 criterion

Posted July 1, 2013 at 11:06 by sbaffini (NuTBox)
Updated December 21, 2016 at 09:10 by sbaffini

The lambda 2 criterion simply concerns the definition of the scalar lambda2 and how turbulent structures can be visualized by proper isosurfaces of lambda2 (like for the Q criterion). Hence, the real difference with the scalar Q is how you compute the scalar lambda2.

This is defined as the second (in magnitude) eigenvalue of the matrix:

S_{ik} S_{kj} + \Omega_{ik} \Omega_{kj}

where:

[LaTeX Error: Syntax error]...
Attached Files
File Type: c lambda2.c (2.6 KB, 467 views)
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