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VOF Coefficient in freesurface cells

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Old   August 12, 2011, 02:12
Default VOF Coefficient in freesurface cells
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Dear Friends
I am simulating 2 phases (liquid-gas), 3D flow around ship and I want to capture wave height in far way. If I choose 0.1 as VOF for interface cells, my results would be match with experimental, while if I use cells with VOF=0.5 for freesurface, results are not accurate. I would appreciate if anyone send or introduce a reference which show I can use 0.1 for freesurface or not.
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Old   August 12, 2011, 13:13
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Originally Posted by mrji8011 View Post
Dear Friends
I am simulating 2 phases (liquid-gas), 3D flow around ship and I want to capture wave height in far way. If I choose 0.1 as VOF for interface cells, my results would be match with experimental, while if I use cells with VOF=0.5 for freesurface, results are not accurate. I would appreciate if anyone send or introduce a reference which show I can use 0.1 for freesurface or not.
definitly not,

to me it seems like a numerical diffusion problem. can you say in how many cells do you have the transition from vof 0 to 1? can you specify the model that you are using (implicit/explicit, transient or steady steate, wich solver, discretization order, wich vof reconstruction method, etc...)
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Old   August 13, 2011, 20:50
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definitly not,

to me it seems like a numerical diffusion problem. can you say in how many cells do you have the transition from vof 0 to 1? can you specify the model that you are using (implicit/explicit, transient or steady steate, wich solver, discretization order, wich vof reconstruction method, etc...)
Thak you so much. the number of cells depend on vessel speed. roughly it is 3 cells. I am using implicit, transient,Gradient=Least Squares Based, Presuure= Presto, Momentun=Second order upwind, volume fration=Quick and second order implicit for transient formulation
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Old   August 18, 2011, 00:59
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Thak you so much. the number of cells depend on vessel speed. roughly it is 3 cells. I am using implicit, transient,Gradient=Least Squares Based, Presuure= Presto, Momentun=Second order upwind, volume fration=Quick and second order implicit for transient formulation
do you think it is correct or not?
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Old   August 18, 2011, 03:50
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looks right.

do you have experiemental data for the whole wake field or just where it touches the hull? if the latter is your case, could you please post a plot of the vof close to the hull, showing the mesh as well?

i would like to check if the problem is just a sort of "numerical surfacial tension" ie high aspect ratio cell causes the flow to rise more that it is expected in the fist cell near the hull.
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Old   August 18, 2011, 22:08
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looks right.

do you have experiemental data for the whole wake field or just where it touches the hull? if the latter is your case, could you please post a plot of the vof close to the hull, showing the mesh as well?

i would like to check if the problem is just a sort of "numerical surfacial tension" ie high aspect ratio cell causes the flow to rise more that it is expected in the fist cell near the hull.
Thanks for replying
Please find the attacheds. I should capture waves in all domain.
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File Type: jpg 61.jpg (21.5 KB, 8 views)
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