Greetings,
I'm encountering a few issues while trying to run a thermal test on a flask with an internal heat load. I've started with a steady state at a low ambient and the natural convection patterns seem to very sensible (see below):
However, when I apply an 800C ambient temperature (under thermodynamic parameters and enivornment radiation) for 30 minutes I seem to generate a downdraught in the main body of air of around 6m/s (see below). As you can see, the flow is entering the domain at the top at around this velocity. I have applied no velocity component to the air, so I am at a loss as to what is causing this. The temperature profile does not look unreasonable, but the only downward flow I would expect would be close to the flask where it is cooling the ambient air. Is there a setting I've missed that might be causing this?
what does it look like if you change the contour plot from temperature to velocity? is it purely the downdraft and the viscosity of the fluid forcing your ambient to move downward? I would expect it to circulate within your cut-plot (depending on dimensions).
Did you use symmetry for this? There is actually an updraft on the right edge (central axis assuming symmetry). This would suggest that perhaps a boundary condition isn't quite right.
There also seems to be some base structure or floor shown in the 1st figure which isn't present in the 2nd. This could alter the overall flow.