I need to determine and plot the variation of the free surface height for water which change with time is there any way to do this knowing that I have 2D pipe flow?

Any suggestions are highly appreciated Thanks a lot

Nobody can answer me the last question? I hope somebody can?

Thank you for any assist KK

It depends where you want to have the height (assuming it varies along the length of your pipe), but you could define a surface (or line if you are in 2d) at the point where you want to know the height. Go to solve/monitors/surface and output a surface monitor on this surface as a function of flow time. Output the integral of the volume fraction for your liquid. After you run the simulation (or even while you are running) you can use gnuplot (or excel) to plot the height by dividing your integral at each time by the known area of the surface on which the integral was taken (or length for a line) relative to the area of your pipe. There are probably other ways you could use a surface monitor to do it as well. Hope this helps. KW

Thank you KW for the reply. I used 2D geometry but I cannot apply what you mentioned for one reason , that is I have problem with my simulations to track the interface correctly and when I tried to view the contours of volume fraction for the secondary phase only one of the phases appear full the pipe do you know the reason for this?

First, what are your boundary conditions? I assume you inlet is a mass flow or velocity with a volume fraction profile or something? Are you using a pressure-outlet with open-channel for your outlet? Are you starting with a patched volume fraction? I assume you are using conditions for which you expect the liquid volume in the pipe to not be full? Anyway, if you are sure you have set things up correctly and the solution is not what you expect, you might need to try different conditions where you are certain that the pipe is not liquid full.

I used two velocity inlets because the velocities of phases not equal and single outlet. The liquid level at inlet is known and its value 19 mm I took this information exactly from an experimental thesis in 1999 , the solution after 30 sec must reach steady state and the liquid level reduced in this case whiel the velocity of gas increases and that of of liquid kept constant at its value. I am not use patch with the solution I used the implicit vof scheme because it's the only method give me reasonable results with respect to the velocity profiles if you want have a look on my case and data files I can send you just send me your email address please.

sure I can take a quick look to better understand what you are asking. kwardle(at)wisc.edu