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Old   March 30, 2009, 19:58
Default BC in closed box simulation
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Miguel Baritto
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Hi,

I am simulating free convection inside a closed box. I have set heat flux at the bottom and insulated walls at the others surfaces. Also, I have set no slip at all the surfaces. However, I have problems with convergence and I think (after read cfx documentation) they are in BCs, since I haven't set pressure nor temperature levels at any BC. Could this be true? if so, how can I set pressure and temperature in a closed and insulated box?

Thanks

Miguel
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Old   March 31, 2009, 17:55
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Glenn Horrocks
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Hi,

I assume you are running a transient simulation - it has to be as you have a hot wall on the bottom and everything else adiabatic so it is going to heat up over time. These type of buoyancy simulations invariably have big transient flow instabilities. You often have to run much smaller timesteps than you would expect to resolve these transient features.

Just set the reference pressure and temperature at the initial temp and pressure, that should be OK.

Glenn Horrocks
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Old   March 31, 2009, 20:16
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Miguel Baritto
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Thanks Glenn,

I will try smaller timesteps.
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