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Pressure drop calculation

Posted Mar 26, 2012, 6:11 a.m. EDT Computational Fluid Dynamics (CFD) Version 4.2a 2 Replies

Harmke van der Velde
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I'm trying to calculate a pressure drop using laminar flow in comsol.

I started with a simple model (see attachment). I also calculated the pressuredrop using the hagen-poiseuille equation but I get different answers.

Hagen poiseuille: en.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation


I have tried this with and without an entrance length and compressible and incompressible. For all these calculations Comsol gives a larger pressuredrop than the analytical equation.

What goes wrong? Is it the model or the analytical equation?

Attachments:

2 Replies Last Post Mar 27, 2012, 6:08 a.m. EDT
Jaap Verheggen
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Posted: 1 decade ago Mar 27, 2012, 5:28 a.m. EDT
I can't open your file, it requires the CAD module.
It's easier if you just apply a pressure difference on inlet and outlet.
Can you try that?

How are you defining the velocity of the fluid at the inlet?
I can't open your file, it requires the CAD module. It's easier if you just apply a pressure difference on inlet and outlet. Can you try that? How are you defining the velocity of the fluid at the inlet?
Amir Fadel
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Posted: 1 decade ago Mar 27, 2012, 6:08 a.m. EDT
Hi,

Your pressure drop is virtually nothing, less than 1Pa, so the differences you see can be deemed to be tantamount to oscillations around the zero.
You may want to try a 2D-axisymmetric model with a much finer mesh.

Cheers




I'm trying to calculate a pressure drop using laminar flow in comsol.

I started with a simple model (see attachment). I also calculated the pressuredrop using the hagen-poiseuille equation but I get different answers.

Hagen poiseuille: en.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation


I have tried this with and without an entrance length and compressible and incompressible. For all these calculations Comsol gives a larger pressuredrop than the analytical equation.

What goes wrong? Is it the model or the analytical equation?


Hi, Your pressure drop is virtually nothing, less than 1Pa, so the differences you see can be deemed to be tantamount to oscillations around the zero. You may want to try a 2D-axisymmetric model with a much finer mesh. Cheers [QUOTE] I'm trying to calculate a pressure drop using laminar flow in comsol. I started with a simple model (see attachment). I also calculated the pressuredrop using the hagen-poiseuille equation but I get different answers. Hagen poiseuille: http://en.wikipedia.org/wiki/Hagen%E2%80%93Poiseuille_equation I have tried this with and without an entrance length and compressible and incompressible. For all these calculations Comsol gives a larger pressuredrop than the analytical equation. What goes wrong? Is it the model or the analytical equation? [/QUOTE]

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