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-   -   Transient free surface with initial conditions (https://www.cfd-online.com/Forums/cfx/24477-transient-free-surface-initial-conditions.html)

 Juan Catelén August 30, 2007 16:12

Transient free surface with initial conditions

I have this problem. I'm trying to simulate a tank with water and air at 6 bar. Suddenly a valve at the bottom is opened and I want to see how the air moves the water through a pipe that is connected to the bottom of the tank. To set the initial conditions I created three domains and I set the volume fractions for each one. When I star the solver I get the following message: floating point exception-overflow. I have made some free surface problems before and I didn't have any problem. What could be wrong? What should I do? Is it possible to fix the initial conditions as I did?

 Glenn Horrocks August 30, 2007 18:31

Re: Transient free surface with initial conditions

Hi,

If the valve and piping are at the bottom of the tank can't you just model the tank as water only with no free surface and just impose a pressure on the top surface? You don't need a multiphase model then and it will be much easier.

Glenn Horrocks

 Juan Catelén August 31, 2007 08:50

Re: Transient free surface with initial conditions

But the one who asked me to do the work wants to know if a "water bullet" can be created with the system. We will have, in the pipe, air, water and air pushing the water. I want to see how this "package of water" flows through the pipe and deforms. And also how could I fix a pressure on top if it would vary with time?

 Glenn Horrocks August 31, 2007 18:33

Re: Transient free surface with initial conditions

Hi,

If you want to know the air/water interface then you need multiphase. Have you read the best practises guide in the documentation on multiphase?

Glenn Horrocks

 Juan Catelén September 3, 2007 08:54

Re: Transient free surface with initial conditions

Yes. I have made a simulation without any problem. But in that simulation I had an inlet and an outlet. The only difference here is that I have only an outlet and the initials conditios are a little more complicated(I have also tried with an opening). Now I'm getting the "floating point exception". Thanks in advance.

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