Hello everyone, I simulate an open channel flow with VOF model, the simulation is unsteady, so the free surface deforms in time, I would like plot this fluctuation in a specific location, for this I must export a volume fraction profile in this location at every time.
Thanks in advance.
1: define a point in the domain, create a monitor, and write this to file (this gives a point profile in time)
Otherwise, define a surface or cell-zone region in your domain. You can do this upfront (during geometry/meshing), or in FLUENT (using surface -> plane or isosurface, or an iso-value region or so; depends on how you want to set the region). Go to calculation activities -> automatic export. There, select the file type you want, the writing interface, the volume or surface to store and the parameters to write.
Thanks for your answer
In fact, in my study I would like to plot the moving of the free surface in a specific section of the channel, for this I must export in each time the location of the interface in this section. Your purpose is available in fixed (x,y) coordinates, but in my case the (y) coordinate of the interface changes in time because the flow is unsteady. See the attached figure
I see. A simple solution would be to define the line S as you do, and write local gas fraction data for that line every timestep. You should be easily able to retrieve the height of the interface y from that line data in a post-processing tool like matlab (or a free euqivalent) or with some python script. If you really want to write a single number directly from FLUENT, you could (assuming you have a single interface and no bubbles or so) write the line-average gas-fraction to file every timestep. After all, this is directly related to the height. Or you may use a macro to compute the y-location with a = 0.5 every step, or write a UDF to do so.
But if you want a single line S, i'd go for the first or second option - depending whether you have a single interface or possible bubbles/droplets that mess up the average.
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