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2 boundary conditions at one interface?

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Old   April 23, 2008, 15:27
Default 2 boundary conditions at one interface?
  #1
YY
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Hi guys,

I want to specify my inlet with a static pressure and a flow rate. Is that possible?

Thanks.

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Old   April 24, 2008, 04:06
Default Re: 2 boundary conditions at one interface?
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Subha
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Hai,

Yes it is possible. After setting the inlet boundary with static pressure, click on the Sources Tab and there you could give a Total Source under Contnuity.

Could you explain why you need such a boudary?

Regards,

Subha.
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Old   April 24, 2008, 07:32
Default Re: 2 boundary conditions at one interface?
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Rogerio Fernandes Brito
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Can I use, for ex., heat flux [W m^-2] and temperature [K]constant on the same boundary contourn (boundary condition)? How come?
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Old   April 24, 2008, 07:58
Default Re: 2 boundary conditions at one interface?
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Andrew
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Why do you want to set the heat flux and the temperature at the wall? That boundary condition would explicitly define the fluid temperature at the wall.
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Old   April 24, 2008, 11:31
Default Re: 2 boundary conditions at one interface?
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YY
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Hi,

Thanks for your reply. I need it because I'm trying to mimic this FSI simulation where the flow rate and pressure is defined. Because if I were to use just the pressure I could not get the flow I want and vice versa. I also tried using total pressure but to no avail. So I guess I'll try what you have suggested.

Thanks again. Really appreciate it.

Regards, YY
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Old   April 24, 2008, 14:49
Default Re: 2 boundary conditions at one interface?
  #6
Rui
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But that Total Source won't be equal to the flow rate.

If you have an Inlet with P1 and an Outlet with P2 (P1>P2), without any mass source (Source=0), you'll have a flow rate (different to zero), right?
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Old   April 25, 2008, 02:12
Default Re: 2 boundary conditions at one interface?
  #7
YY
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Hi,

I have tried using the source option but the results are not what I want. I'm basically modelling flow in a circular pipe. I would like to set a Reynolds number and a static pressure at the inlet. Any advice guys? How exactly do you use the source option. I'm very confused. Thanks people.

Regards, Yi Yong
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Old   April 25, 2008, 07:43
Default Re: 2 boundary conditions at one interface?
  #8
Andrew
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What is your outlet condition? Specifying pressure at the inlet and the outlet is typically avoided. If you want to set the pressure at the inlet, you can set the mass flow at the outlet to get the desired Reynolds number.

Note that if you set the pressure at the inlet and outlet and also specify the mass flow at the inlet, your system is overdetermined and will not converge, even if the mass flow and pressure conditions are taken from real measurements.
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Old   April 25, 2008, 11:54
Default Re: 2 boundary conditions at one interface?
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YY
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hey,

My outlet is just a 0 static pressure outlet. Yea I would think so too. Haven't done a CFD specifying 2 b.c's at one place but apparently the PHD thesis which i'm following, the person applied a velocity and pressure at the inlet.

Regards, Yi Yong
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