Dear Ricardo,
I have adjusted the velocity inlet to 0.004m/s , and it works, thank you.
However, I still don’t fully understand why .
If i use the Gr number to calculate the nature convection, or to be more, I assume the pressure gradient is purely turned into kinetic energy, then the velocity caused by such a 20K temperature even with characteristic length of 0.02m should also be the scale of 10^-2.
Also an experience equation from the following page offers the similar result (but maybe not accurate) ,
Using this equation, if I focus on the height of 0.01 m, the velocity should be 0.16m/s.
in any theory, the scale should be no less than 10^-3, which should show some result in average velocity magnitude while there is not.
Also, I have another project with similar situation where the domain area is 12m*5m, still i cannot see any uphill trend.
link below - simulation- run 20