insulated container divided into equal volumes by a partition
Hi,
my goal is to model the following problem: A gas is confined to one side of a rigid, insulated container divided into equal volumes by a partition. The other side is initially evacuated. The partition is removed, and the gas expands to fill the entire container. Assuming ideal gas behavior, determine the final equilibrium pressure. I tried two ways to do this: first using two domains of fluid with an fluid-fluid interface, then using cell expression language to do a global initialization for a single fluid domain. But my results until now have been unsuccessful. Anybody knows how to simulate this kind of problem? |
I guess the first question is why not just use the back of an envelope rather than a CFD solver! I assume you have your reasons?
Did you run this as steady-state? In steady-state mass is not going to get conversed during convergence, so I think you would need to run this as a transient case. Unfortunately that would be difficult to converge due to the high mach numbers in the evacuated space. Perhaps there's an expert parameter for the steady state case - anybody? |
There are no expert parameters which will help. Stumpy's comment is correct - sounds like a first year uni thermodynamics question which can be solved in a few minutes with the ideal gas laws.... So why bother with CFD?
It will be a tricky CFD simulation with all sorts of nasty initial transients. |
Not sure if this would work, but if you set it up as a multiphase case with initial conditions set so the volume fraction of gas is 1, then you may be able to run steady-state. For steady-state multiphase cases in a closed system a global correction is applied to converse the mass of each phase.
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simulate a burst disc
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something like that
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http://www.drthfrank.de/publications...ensation_b.pdf |
What are you trying to get out of the analysis? Your first post only mentioned the final pressure, but now you are talking about a burst disc.
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I assume you mean the final steady state mixed result for the "first problem".
So is your question how can you make the opening suddenly appear? |
yes
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Lots of ways.
1) Define an initial condition with different conditions on each side. This is the easiest way. 2) Do a simulation to define the initial conditions where they are not connected (maybe a wall in the gap). Then use this as an initial condition on a simulation with the gap connected. 3) Put a source term, probably a momentum source, in the gap which initially stops flow (or at least greatly slows it down) and then dissappears. 4) Use a GGI and a sliding interface to slide it open. 5) Use moving mesh to open a connection up. I could probably think of more if I could be bothered. But option 1 is simplest so go with that if it is suitable. |
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