Hello,

I want to simulate natural convection in a simple chimney. I don´t 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? I´ve read in a tutorial that I should set the operating density to 0.??

Thank you for your help!

Thomas

I've had good results setting the operating density to the density at approximately the mean gas temperature.

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??

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.