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how to simulate exhaust of high pressure tank

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Old   January 7, 2009, 02:28
Default how to simulate exhaust of high pressure tank
  #1
song
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Hello, everyone

There are two tanks connected with pipe, one tank has a high pressure of 10 atm and the other one 1atm, by controlling the valve at the middle of the pipe, the high pressured air will be exhausted to the low pressure tank...

first, i just want to simulate the high pressure tank in 2D, one outlet/open outlet set, and the reference pressure is set to be 1atm, the relative pressure in initialization is 9atm, that's ok, i thought.

but the factor is, cfx can't calculate it, i don't know why.

is there anybody interested in this project? could you give me some hints?

thanks in advance.
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Old   January 7, 2009, 18:32
Default Re: how to simulate exhaust of high pressure tank
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Glenn Horrocks
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Hi,

Can you describe how you have set it up? What fluid are you using? What physics?

Glenn Horrocks
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Old   January 9, 2009, 19:17
Default Re: how to simulate exhaust of high pressure tank
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Tristan
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We had some problems getting a run started for high pressure air flow through a manifold. One way to get the run started was to prescribe an initial pressure field with a linear pressure drop between the inlet and the outlet. If we used a 1 atm reference pressure (as you did) and then a constant initial pressure field, the mach number would blow up in the first few steps.

Tristan
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Old   January 11, 2009, 17:54
Default Re: how to simulate exhaust of high pressure tank
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Glenn Horrocks
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Hi,

There are many ways to get tricky transonic simulations to converge, Tristan has mentioned one. Others include starting at a low pressure and ramping the pressure up, starting with upwinding and switching to a higher order scheme later, starting with local timestepping and switching to physical timestepping later, starting on a coarse grid and interpolating to a fine grid for the final run, sometimes expert parameters such as increasing the number of continuity loops helps....

Glenn Horrocks
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