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Specifying operating temperature in buoyancy flow

Hi,

Could someone please explain to me how to specify the operating temperature in buoyant flow using the Boussinesq approximation.

If modelling a long tube with pressure inlet / outlet and a cold tube part in the middle section how should the To value be specified? Same as temperature on pressure inlet or same as temperature on cold wall?

The results will differ depending on which value I choose.

 Evan Rosenbaum June 28, 2006 11:41

Re: Specifying operating temperature in buoyancy f

For an open system, the value doesn't matter much. Don't use Boussinesq for a closed system.

Re: Specifying operating temperature in buoyancy f

Hi Evan,

I tried simulating a long vertical tube 0.05 m ID, 1.0 m long. Middle section (0.2 m) was held at 273 K while pressure inlet (top of tube) was held at 293 K / 0 gauge and pressure out (bottom of tube) was held at 293 K / 0 gauge as well.

The results varied dependent on the operating temperature chosen which according to you it shouldn't. Am I doing something wrong?

Re: Specifying operating temperature in buoyancy f

Just a thought - would it be possible / useful to make a UDF which applies the Boussinesq approx. locally, i.e. the buoyancy force for a cell is calculated from the mean temperature of the surrounding cells?