Hi..all please help !! the detail of my model are 1. natual convection between the gap of double-wall 2. I set inlet openning as pressure inlet and set outlet openning as pressure outlet 3. double-wall are difference temperature.

I have problem about How to set material type (fluid is air) I try ideal gas, incompress-ideal gas, Boussinesq but not work then I would like to define density upon temperature. Do you have any suggestion ?

If I would like to define density as density=352.2057/(Temerature)

What should I do and Can I use polynomial ?

Thank you for advance help !

The`am

If you don't understand. i am sorry, about poor in English

hi Why can't work when setting ideal gas, incompress-ideal gas, Boussinesq?you must make sure the operate condition have been setted. If you would like to define density as density=352.2057/(Temerature), 1.you can get the real curve . 2.use the piecewise polynomial approimation to instead of the inverse function. hope these can help you.

If you tried ideal gas, incompressible ideal gas and Bossinesq and none of them worked, I suspect you may have applied gravity in the wrong vector. Double check you gravity specification.