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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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Old

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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Old

Workbench meshing - 1

Posted June 27, 2013 at 08:16 by kartrmswy

So I modeled (with some difficulty) a concentric heat exchanger pipe on ANSYS WB Design modeler, and found that it's not that difficult to start using. However, the main challenge encountered was in the mesh, wherein the automatically generated mesh proved to be too extensive (even with a coarse relevance center) and the total number of nodes was in the order of 20,00,000 - this was going to take very long even on the 8-core machine I was working on.

I need to change the mesh...
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Fresh sonicFoam NACA airfoil results

Posted May 29, 2013 at 05:52 by skeptik (CFD notes)

pretty good results. but i need to simulate airfoil with trailing edge flap so i need accurate Cp at x/c=1.

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Airfoil NACA 23012 results, transonic flow

Posted May 28, 2013 at 05:38 by skeptik (CFD notes)

What i've got about my airfoil (exp and Fluent data were extracted from article, but it's in russian. originally exp data from TZAGI report)
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So there present oscillations, they were caused by second order schemes. I'll simulate it on upwind later.

The differences in p fields are showed here:

upwind
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linear corrected 1
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