# SimpleFoam Laminar Pipe Flow Pressure Drop Error

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 September 13, 2019, 09:10 SimpleFoam Laminar Pipe Flow Pressure Drop Error #1 New Member   Xiaolong Liu Join Date: Sep 2019 Posts: 6 Rep Power: 2 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/s/w91ak3klx3..._flow.zip?dl=0 Thanks, Xiaolong

 September 16, 2019, 09:26 #2 New Member   Xiaolong Liu Join Date: Sep 2019 Posts: 6 Rep Power: 2 Anyone has some insight in this?

 September 16, 2019, 10:57 #3 Senior Member   Join Date: Sep 2013 Posts: 230 Rep Power: 12 Your viscosity in transportProperties ("1e-06; //water") does not match what you specified Code: ```Dynamic viscosity (mu): 8.9e-4 N/m-s Density (rho): 997 kg/m^3```

September 16, 2019, 11:37
#4
New Member

Xiaolong Liu
Join Date: Sep 2019
Posts: 6
Rep Power: 2
Quote:
 Originally Posted by Bloerb Your viscosity in transportProperties ("1e-06; //water") does not match what you specified Code: ```Dynamic viscosity (mu): 8.9e-4 N/m-s Density (rho): 997 kg/m^3```
Hi Bloerb,

Thank you very much. I didn't realize I messed up with my data. Now it's matching.

Best,
Xiaolong