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Hello everybody!

I have a problem when modelling convection in a close box (rectangular shape) using general heat transfer module and weak compressible navier-stokes module coupled. I wanna know the profiles of heat flux and velocities on the fluid (argon, gas) but... My models don't converge... I think this can be solved in a simple mode, but i really don't figure out, yet. Can anyone post a solved model like this?

Description of my model:

Rectangular box, (0,80 m in x, 2,8 m in y)
Material Library: Argon (gas form)

General Heat Tranfer
Physics: default
convective box checked, velocity field marked as "u" and "v", Pa = 1[atm];
initial temperature=25[degC];
Bondary settings: botton: Temperature=(25+0.7*t[1/s])[degC]; all others: Insulation

Weakly Compressible Navier-Stokes
physics: all default, plus Fy=-9.8[m/s^2]*rho_chns
stabilization tab: all default
initial: u,v =0 (both), Po=1[atm]
Bondary Settings: wall, no slip (all them)

The time evolution that I tried was 100 seconds

I've already tried:

- Refining meshes
- Changes the solver
- Using a bondary condiction of heat flux instead Temperature (in general heat transfer, botton of box)

I always only find this message:

Error:
Failed to find consistent initial values.
Last time step is not converged.

Thanks for reading, sorry for the long text. :)