Contours of 2D plotting

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April 12, 2010, 11:15
Contours of 2D plotting
#1
Member

Yang Yue
Join Date: Feb 2010
Location: Birmingham, UK
Posts: 36
Rep Power: 14
Hello fellas,

I have a question about the result plotting in 2D.

I've chosen NF value as the contour variable and contour type is colour shaded. The snapshots of the ploted result have white lines indicate the free surface of the fluid (I guess) as showed in the attachments. The blue grids repersent the flow while the red grids are voids.

Since the deep blue grids do not have free surface, if the white line shows the free surface, it should be above the blue grids. This doesn't correspond to the plotting results. However, the white line shows a more realistic free surface of the flow in the attachment which modelled a plunging jet.

So my question is how this white line been plotted? Which data is used to plot the white line of the free surface in 2D?

Cheers!

Yang

Attached Files
 plunging jet.pdf (47.9 KB, 60 views)

April 14, 2010, 10:28
#2
Senior Member

michael barkhudarov
Join Date: Mar 2009
Location: Sante Fe, New Mexico, USA
Posts: 336
Rep Power: 16
Quote:
 Originally Posted by therockyy Hello fellas, I have a question about the result plotting in 2D. I've chosen NF value as the contour variable and contour type is colour shaded. The snapshots of the ploted result have white lines indicate the free surface of the fluid (I guess) as showed in the attachments. The blue grids repersent the flow while the red grids are voids. Since the deep blue grids do not have free surface, if the white line shows the free surface, it should be above the blue grids. This doesn't correspond to the plotting results. However, the white line shows a more realistic free surface of the flow in the attachment which modelled a plunging jet. So my question is how this white line been plotted? Which data is used to plot the white line of the free surface in 2D? Cheers! Yang

Yang, the white line is drawn based on the fluid fraction F. It is the contour line of F=0.5 since in the void F=0 and in the fluid bulk it is 1.

May 5, 2010, 07:50
#3
Member

Yang Yue
Join Date: Feb 2010
Location: Birmingham, UK
Posts: 36
Rep Power: 14
Quote:
 Originally Posted by MuxaB Yang, the white line is drawn based on the fluid fraction F. It is the contour line of F=0.5 since in the void F=0 and in the fluid bulk it is 1.
Thanks, Michael.

A quick question: Is the free surface plotted in 3D also based on the volume of fraction of the cell?

I just feel confused about the NF value and the fraction of fluid. Can I explain this like that the NF value is the flag to lable the surface cell, but the calculated free surface is plotted by fuid fraction? Is that the concept of the volume of fluid method?

Thanks a lot!

Yang

 May 5, 2010, 12:09 #4 Senior Member   michael barkhudarov Join Date: Mar 2009 Location: Sante Fe, New Mexico, USA Posts: 336 Rep Power: 16 Yang, You are right, NF is used for labeling free surface cells, while fluid fraction is used for plotting in 2d and 3d. I am not sure the NF flag is part of every VOF method, but it is certainly useful in FLOW-3D.

 December 22, 2012, 16:04 fluid depth #5 Senior Member     Fatema Zandi Goharrizi Join Date: Mar 2009 Posts: 158 Rep Power: 15 Hi friends, How we could get results in post processor part for fluid depth (e.g. in a free surface modelling) along the geometery?