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#1 |
Member
Yuanwei Cao
Join Date: Jun 2017
Location: Munich,Germany
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Hi researchers,
Anyone simulate a bubble in still water without gravity using interFoam? If so, how is the result should be? Best Regards CYW |
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#2 |
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Without gravity you will probably get a solution that is heavily corrupted by parasitic currents.
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#3 |
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Yuanwei Cao
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Thank you for your reply. I have simulated such a case. But the bubble evolves in a weird direction. I do not know the reason. What is " parasitic currents"? Is that to say, interFoam cannot simulate such a case?
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#4 |
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Parasitic currents are a numerical problem that occur at the bubble interface where the pressure difference is high. As far as i know there is no general solution to this problem yet in VOF type solvers, even commercial codes like FLUENT. You can search this forum for more. What you see in your simulation is probably weird behaviour because of this. When you activate gravity these parastic currents get overlapped by the rising velocity of the bubble. Don't ask me how this works numerically but you can get a meaningful and accurate description of the rising behaviour (velocity, shape) nevertheless.
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#5 | |
Member
Yuanwei Cao
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Quote:
Also this thread helps me a lot. parasitic currents Thank you for your kind reply |
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#6 | |
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#7 |
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Yuanwei Cao
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#8 | |
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I've never done it, since my assumption was that the pressure field is calculated with the first time step. It would be interesting to know how we can set a pressure Field in OpenFoam, i guess with setFieldsDict... |
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#9 |
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Yuanwei Cao
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That is true. I set different pressure in air and water phase with setFieldsDict. But the result did not get better...
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#10 |
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#11 | |
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Yuanwei Cao
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Quote:
/*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 2.3.0 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; location "system"; object setFieldsDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // defaultFieldValues ( volScalarFieldValue alpha.water 1 volScalarFieldValue p_rgh 1e5 ); regions ( sphereToCell { centre (0 0 0.3); radius 0.15; fieldValues ( volScalarFieldValue alpha.water 0 volScalarFieldValue p_rgh 2e5 ); } ); // ************************************************** *********************** // |
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#12 | |
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Shame it does not help with the parasitic currents... May i ask what you need the stagnant bubble for? If you have a bubble that is perfectly shaped (depending on diameter and surface tension) you can simulate under gravity a few time steps and the bubble should not deform, than this time step should not contain parasitic currents anymore (it does contain rising velocity filed though..) |
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#13 | |
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Yuanwei Cao
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This is a preliminary research for my PhD work. My final goal is to simulate bubble condensation. Later compressibleInterFoam will be used. Do you know how to set alphaSgs file and what is it? |
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#14 | |
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This seems to be related to a LES turbulence model... Not sure though.. |
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