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how to plot Cp for unsteady flow past a cylinder

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Old   April 16, 2013, 20:41
Default how to plot Cp for unsteady flow past a cylinder
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Roger Liu
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how to plot Cp for unsteady flow past a cylinder?
I use pimpleFoam to calculate Cd and Cl.
but how to calculate Cp? and finally plot it vs. X Position
Thanks!
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Old   April 16, 2013, 22:49
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HECKMANN Frédéric
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You can use Paraview to plot this. Just open your case, then use the calculator to compute the Cp by your own. Just apply the formula drom Cp.

The calculator looks like this:
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Old   April 16, 2013, 23:20
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hi
What expression for example is suitable for total pressure?
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Old   April 17, 2013, 00:04
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Quote:
Originally Posted by fredo490 View Post
You can use Paraview to plot this. Just open your case, then use the calculator to compute the Cp by your own. Just apply the formula drom Cp.

The calculator looks like this:
but the Cp I want to plot (vs. X position) is just around the object (e.g. cylinder), how can I capture the pressure value on the cylinder surface??

Thanks!
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Old   April 17, 2013, 00:09
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1) open your case with the wall only (or any patch)
2) use the calculator to get Cp
Cp = (P - P_inf) / (1/2 * rho_inf * V_inf ^ 2)
If you have a decomposed part, you need to select the step 1 (and not 0) to do the calculation. It seems that there is a bug if you use the first step.
3) use the filters -> plot on intersection curve to get the curve.


You can also use the sampling function from openfoam but I never use it so I don't have any example. http://www.openfoam.com/features/run...processing.php
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