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LES in Fluent: channel flow test case

Posted July 1, 2013 at 11:12 by sbaffini (NuTBox)

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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Lambda-2 criterion

Posted July 1, 2013 at 11:06 by sbaffini (NuTBox)

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]...
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File Type: c lambda2.c (2.6 KB, 248 views)
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3D Panel Method

Posted July 1, 2013 at 11:03 by sbaffini (NuTBox)

Some open/free 3D panel method tools:

APAME
http://www.3dpanelmethod.com/home.html

PANAIR (A502)
http://www.pdas.com/contents15.html (look for Panair - A502)

If you are looking for something more didactic, i suggest:

http://www.dept.aoe.vt.edu/~devenpor/aoe5104/

But it seems that the material is not available when the course is not active.
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The role of pressure for incompressible flows

Posted July 1, 2013 at 10:34 by sbaffini (NuTBox)

If we consider the continuity and momentum equations for a general compressible fluid:

\frac{\partial \rho}{\partial t} +
\frac{\partial}{\partial x_j}\left[ \rho u_j \right] = 0


\frac{\partial}{\partial t}\left( \rho u_i \right) +
\frac{\partial}{\partial x_j}
\left[ \rho u_i u_j + p \delta_{ij} - \tau_{ji} \right] = 0

taking the time derivative of the first one and the divergence of the second one:...
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Heat Exchanger Resistance

Posted June 28, 2013 at 07:31 by ryaron

The method I have given earlier is known as perturbation significance analysis.
Quote:
Originally Posted by ryaron View Post
What are the ratios of the conductivities ?
i.e. k1/k2 ?
Here's a quick answer:
make two dimensionless parameters epsilon=k1/k2 and eta characteristic length tube/characteristic length plate, make sure they are << 1.

Denote them as epsilon and eta.
Now expand both expression you've written in powers of epsilon and eta.
The one with the higher order O(epsilon^n),
...
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