I am now using unsteady VOF method to compute the free surface flow (air and liquid). I have obtained the contours of these two phases at different time. But I was confused that I could not obtain the coordinate value of the interface. Does anyone know how to obtain them?

Ups I posted the answer to the wrong question - here is the solution (again)- i hope

Hi!

What you should do is: go to "surface-iso surface". Then set surface of constant density - set iso values to desired density for example 500kg/m^3 if you have water air problem. This defines a line of cnstant density (the line of interface). Chose the name for the surface, for example denity500 and click create.

To get the coordinates go to "plot-xy plot". Deselect "position on x axis". set "Y axis function to grid - y coordinate" and "x axis function to grid x coordinate. Select "density500" at surfaces. If you want to get the numerical values (instead of plot) select "write to file"..

Hope this helps...

MATEUS

Thank you very much, MATEUS. What you said helps me a lot. One thing I can not understand is why the density is set to 500 kg/m3, not other values for water air problem.

Hi!

Well that's aproximatelly the mean density value (0.5*(rho_water+rho_air)). Since Vof uses a mixture fluid approach you get more or less steap density gradient at the interface. So the middle value should determine its mean position (it's about the same if you use contour plot with only 2 levels). If your simulation is good there should't be much difference if you chose other value anyway.

Best regards

MATEUS

I see. You are so kind, MATEUS. Many thanks to you.

Best regards

Ryan