Post processor - how to view only specific part water by 'age of fluid' etc

s.petley · August 20, 2015, 07:30

I'm looking at the water flows in a Pelton casing, however to get the water jet to initialize I let run for a number of timesteps before it interacts with the bucket, therefore this water is present in the casing when I visualize an isosuface etc.

I was wondering if there is a way to get rid of this water by only looking at the isosurface starting with water from 0.05 seconds say.

I've read that I could do an 'age of air' type calculation, however this is implemented in pre, I wonder if there is an alternative so I don't have to run the simulation again.

Kind regards,
Sean

ghorrocks · August 20, 2015, 18:20

Can't you just look at the simulation at a time step far enough from the start that the startup transient has gone?

But to answer your question: I cannot think of a rigorous way of doing this in post processing only. You could put streamlines on the inlet that only last a certain amount of time - but I can't see how to then convert this into the water region which is new and discard the old stuff.

August 20, 2015, 07:30	Post processor - how to view only specific part water by 'age of fluid' etc	#1
s.petley New Member Sean Petley Join Date: Oct 2014 Location: Lancaster, UK Posts: 8 Rep Power: 11	I'm looking at the water flows in a Pelton casing, however to get the water jet to initialize I let run for a number of timesteps before it interacts with the bucket, therefore this water is present in the casing when I visualize an isosuface etc. I was wondering if there is a way to get rid of this water by only looking at the isosurface starting with water from 0.05 seconds say. I've read that I could do an 'age of air' type calculation, however this is implemented in pre, I wonder if there is an alternative so I don't have to run the simulation again. Kind regards, Sean

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August 20, 2015, 18:20		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Can't you just look at the simulation at a time step far enough from the start that the startup transient has gone? But to answer your question: I cannot think of a rigorous way of doing this in post processing only. You could put streamlines on the inlet that only last a certain amount of time - but I can't see how to then convert this into the water region which is new and discard the old stuff.