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Problems in assigning inlet-outlet boundary condition for a two phase flow
Posted 21 nov 2014, 05:25 GMT-5 Fluid & Heat, Computational Fluid Dynamics (CFD), Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 5.1 1 Reply
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I am trying to simulate a laminar two phase flow passing over a cylinder with a phase-field model where the cylinder is submerged into the water (heavier fluid), as a part of my project. I have tried a couple of candidates for the boundary condition at the inlet and the outlet. Initially, I gave a uniform velocity at the inlet for both phases plus a zero pressure at the outlet, then I assigned a mass flow rate for both phases and mass flow rate at the exit and a few other failed attempts. Also I have tried to give a step function at the inlet for the volume fraction at the level of my free surface and give a uniform velocity which I could not even implement.
Receiving a piece of advice, I have recently tried to give a zero pressure gradient at both sides and a body force or a small acceleration in the x-direction (as my driving force), but it seems that after sometime (4% of run-time in my case) the "reciprocal of the step size" increases and causes a failure.
I would be glad if there is a solution for the problem. I also attached the basic model here.
Amin,
Hello Amin Rahmat
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In laminar flow and in outlet boundary condition if we choose laminar outflow then there will be three options in which one of them is exit pressure ,i f select exit pressure we need to mention two options one is exit pressure and exit length .
My question is
1- what is exit length and how to calculate it ?
2-At what case we should use laminar flow ? if you have any material regarding this please share
Thank you in advance
Regards