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how can i give a boundary condition with pressure and velocity together

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Old   December 9, 2010, 16:04
Default how can i give a boundary condition with pressure and velocity together
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hi everyone

inlet boundary condition= pressure 10Pa and velocity 10m/s
outlet boundary condition= pressure 10Pa and velocity 10 m/s


how we give a boundary pressure and velocity conditions together?

thanks thanks thanks
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Old   December 9, 2010, 21:02
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akhenathon,

See my post to your same question in another thread.

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Old   April 24, 2012, 17:03
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ComputerGuy,

would you be able to post a link to the thread you are referring...
Many thanks
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Old   April 24, 2012, 17:52
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two boundary condition on an edge or face

I think this person was trying to over-prescribe the boundary conditions for the system.

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ComputerGuy

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ComputerGuy,

would you be able to post a link to the thread you are referring...
Many thanks
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Old   April 24, 2012, 18:04
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I have seen people deal with a similar problem where one needs to set pressure and certain velocity vector at inlet while performing a compressible flow calculation...

In a vortex tube calculation, Skye et al (Int. J. Refrig.) made a small-area anular opening at one end of a pipe, then defined the vector direction in cyllindrical coordinates. A high enough inlet pressure on the small area inlet gave the nearly sonic inlet velocity they needed. They adjusted the area until the mass flux was also what was expected to be reasonable.

If there are any other ideas how to achieve a similar scenario flux/pressure/velocity vector, I'd be very interested to read about it
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Old   April 24, 2012, 18:23
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Just to be clear, the original poster asked how to set BOTH the pressure and velocity (mass flow) at BOTH the inlet and outlet. Perhaps I'm missing something, but isn't that generally an overspecified problem?

If you're OK with performing an iterative calculation to solve for the pressure and mass flow, that's a whole other question. However, I see no way to prescribe them as boundary conditions.

ComputerGuy

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I have seen people deal with a similar problem where one needs to set pressure and certain velocity vector at inlet while performing a compressible flow calculation...

In a vortex tube calculation, Skye et al (Int. J. Refrig.) made a small-area anular opening at one end of a pipe, then defined the vector direction in cyllindrical coordinates. A high enough inlet pressure on the small area inlet gave the nearly sonic inlet velocity they needed. They adjusted the area until the mass flux was also what was expected to be reasonable.

If there are any other ideas how to achieve a similar scenario flux/pressure/velocity vector, I'd be very interested to read about it
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Old   April 24, 2012, 18:32
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I agree with your reasoning...

My post was a bit of a diversion; I wanted to make the point that to define pressure + velocity vector on an inlet boundary takes planning of the area etc
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