[fanta]

Hi,

i am new to OpenFOAM, but i have done my first simulations with simpleFoam.
To verificate my studies i want to do a classic example.
I have a Pipe with 1m length, 0,01m diameter. Through that pipe i have a flow with water at 20 °C with 0,1 m/s. I made a 3D model of the pipe with Solidworks, exported it to STEP and meshed it with SALOME, being carefully about the units, because it has to be converted in meters. Now when i run the study at the end i do a "postProcess -func 'patchAverage(name=inlet, p)'" i get a pressure that i have to multiply with rho. The result of that is 56 Pa. The analytical result of my calculation with the Law of Hagen-Poiseulle is 32.064 Pa. Now my first question is, why is there so much difference between the analytical result and the simulation?

My second question is: I did a "postProcess -func "totalPressureIncompressible(p,U)"", but the result is 0.006 Pa. Why is that?

The whole case is around 44 MB including the STEP file and the UNV Mesh, so where to upload? I don't have an own webspace.

Regards, fanta

[fanta]

Hi,
i uploaded the case to google drive:

https://drive.google.com/file/d/0BwY...ew?usp=sharing

Regards, fanta

[walakaka]

Originally Posted by fanta

Hi,

i am new to OpenFOAM, but i have done my first simulations with simpleFoam.
To verificate my studies i want to do a classic example.
I have a Pipe with 1m length, 0,01m diameter. Through that pipe i have a flow with water at 20 °C with 0,1 m/s. I made a 3D model of the pipe with Solidworks, exported it to STEP and meshed it with SALOME, being carefully about the units, because it has to be converted in meters. Now when i run the study at the end i do a "postProcess -func 'patchAverage(name=inlet, p)'" i get a pressure that i have to multiply with rho. The result of that is 56 Pa. The analytical result of my calculation with the Law of Hagen-Poiseulle is 32.064 Pa. Now my first question is, why is there so much difference between the analytical result and the simulation?

My second question is: I did a "postProcess -func "totalPressureIncompressible(p,U)"", but the result is 0.006 Pa. Why is that?

The whole case is around 44 MB including the STEP file and the UNV Mesh, so where to upload? I don't have an own webspace.

Regards, fanta

I'm not an expert!

But check that you calculate your pressure gradient only against the developed region of your flow. (Take the pressure difference within the developed region and divide it by the length of the developed region).
To my understanding the H-P equation is only legitimate when calculating developed flow.

Regards
Shafik