# Issues with Modeling Laminar Pipe Flow Using Cyclic Boundary Conditions

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 February 16, 2021, 16:34 Issues with Modeling Laminar Pipe Flow Using Cyclic Boundary Conditions #1 New Member   Join Date: Dec 2019 Posts: 11 Rep Power: 6 Hello, I am trying to model laminar flow inside of a duct with square cross sections. I am using cyclic bundary conditions and I am starting with simplefoam to solve for a steady-state solution. I set the inlet and outlet boundary conditions to be "cyclic" and specified Ubar to be 0.04m/s. The axial velocity profile looks alright and is quite close to the analytical solution calculated using the pressure gradient printed out after each iteration. However, my simulation has two major problems: 1. The residual from the pressure solver is very high and fluctuates at around 0.28, and the residuals from the velocity solvers are also much higher than the case where the boundary conditions are not cyclic; 2. The pressure distribution shown in paraview does not match the pressure gradient provided by the solver from the terminal. I was expecting the pressure to be droping linearly from the inlet to the outlet, but instead it is close to zero throughout the channel and oscillates at an amplitude of 1e-10. I have included some of my codes in the attachment. I'd wish to know how to model a laminar pipe flow using cyclic boundary conditions and what are the causes of the problems I've encountered. Thank you very much! blockMeshDict.txt controlDict.txt fvSchemes.txt fvSolution.txt fvOptions.txt

 June 9, 2021, 03:21 #2 Senior Member   mohammad Join Date: Sep 2015 Posts: 274 Rep Power: 11 Hi, Can you please just tell me whether you found any solution for this problem? Thank you for your help in advance, Mohammad

June 10, 2021, 15:03
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Hi, unfortunately I did not find a solution to this problem, and eventually I gave up using cyclic BCs. I hope you have better luck!

 June 10, 2021, 21:04 #4 Senior Member   mohammad Join Date: Sep 2015 Posts: 274 Rep Power: 11 Hi, Thank you for your great reply. I am still struggling with that. What method did you use instead of that?

June 11, 2021, 10:09
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 Originally Posted by mostanad Hi, Thank you for your great reply. I am still struggling with that. What method did you use instead of that?
Good luck!