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Pressure drop error of laminar pipe flow with simpleFoam

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Old   September 11, 2019, 12:39
Default Pressure drop error of laminar pipe flow with simpleFoam
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Xiaolong Liu
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Hello Foamers,

I am new to openfoam. I am trying to simulate a laminar pipe flow by using simpleFoam and compare the pressure drop with the analytical solution. However, I found a quite consistent about 11% pressure drop error by adjusting the inlet velocity (Re=500, 1000, 1500, 2000)

Below are the parameters I used for this simulation

Pipe length (L): 0.5m
Pipe diameter (D): 0.015m
Dynamic viscosity (mu): 8.9e-4 N/m-s
Density (rho): 997 kg/m^3
Max value of parabolic velocities:
(1) 5.96e-2 m/s(Re=500); (2) 1.19e-1 m/s (Re=1000); (3) 1.78e-1 m/s (Re=1500); (4) 2.38e-1 m/s (Re=2000).
Boundary conditions:
p:
Inlet: zeroGradient;
Outlet: fixedValue uniform 0;
Wall: zeroGradient;
U:
Inlet: parabolic velocity (I tried fixedvalue uniform inlet velocity as well without measuring in the entry length region, the same problem);
Outlet: zeroGradient;
Wall: fixedValue uniform (0 0 0);


I also compared simulation results with Fluent, as shown in the figure below:

https://www.dropbox.com/s/22xv8hlwuv...luent.png?dl=0

I have tried (1) refining the mesh in different levels; (2) adjusting the gradient scheme to leastsquares method; (3) importing the mesh developed in ANSYS for Fluent simulation. None of these can change the results.

Since this is a very simple case, I believe simpleFoam should be able to provide accurate prediction on the pressure drop. However, I just can not get it.

I really appreciate if anyone can help to point out what the problem is.

Please find my code in the following link:

https://www.dropbox.com/sh/3ow6w0cvx...LbEbgwH_a?dl=0

Thanks,
Xiaolong

Last edited by xiaolong; September 12, 2019 at 08:34. Reason: To make a statement more clear
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Old   September 12, 2019, 02:45
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anonymous
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Hi!
Sorry, I was wrong, but I can't delete the post.
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Old   September 12, 2019, 08:27
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Xiaolong Liu
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Hi simrego,

Thanks for your quick reply though.

Xiaolong
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Old   September 16, 2019, 10:51
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Xiaolong Liu
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Just got pointed out by another foamer. I set wrong value of nu in transportproperties. Now they match.
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laminar pipe flow, pressure drop error, simplefoam

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