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Old   March 14, 2005, 12:06
Default BCs natural convection??
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Thomas
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Hello,

I want to simulate natural convection in a simple chimney. I dont want to use the boussinesq modell, as delta T is about 40 K. I have a pressure inlet at the bottom and a pressure outlet at the top. The sourrunding walls have a temperature condition.

How do I have to specify to density when I use the incompressible ideal gas law?

How do I specify the operating density? Ive read in a tutorial that I should set the operating density to 0.??

Thank you for your help!

Thomas
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Old   March 14, 2005, 13:11
Default Re: BCs natural convection??
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Evan Rosenbaum
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I've had good results setting the operating density to the density at approximately the mean gas temperature.
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Old   March 15, 2005, 03:33
Default Re: BCs natural convection??
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Thomas
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Did you use the the incompressible-gas-law or the boussinesq modell? So for example: Incompressible gas-law: Operating pressure: 102325 Operating Temperature: 288.16 Operating: Density: 1.225

As the opertation temperature is coupled withe the operating density, I think I have to adapt the density and temperature to my problem. Right??
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Old   March 15, 2005, 13:08
Default Re: BCs natural convection??
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Evan Rosenbaum
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We have typically used a piecewise linear density for fluids and ideal gas for gases. You only need the operating density as a reference point for computing local buoyancy force, so the exact value isn't overly critical as long as it falls in your actual range of local densities.
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