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Hi,

I´m trying for several months now and cant find a solution. In the end, I want to model the charging process of a hot water storage. Whenever I am running my model, there wont be a real temperature stratification. I have extreme mixing effects.

I implemented conditions like gravity, I tried modeling incompressible with boussinesq as well as weak compressible. I tried direct and iterative solver and a super fine mesh (biggest element 0.01 m), also constant small time steps. Furthermore I already tried even slower inlet velocity down to 0.005 m/s.

In the current model, I only solve upper half of the storage tank. So I defined the whole area down area as the outlet. I also tried simulating the hole storage with an discharge unit (same as inlet). But this has no effect on my problem.

For me it looks like the convection in the water is calculatet to high, because without flow model (only heat transfer) there is only small temperature change. Also inlet velocity profile looks correct, since water is creeping out of the inlet and directly rise to the top.

Still, there is no hot temperature layer on top, even after 12 h of charging.

I am not an expert in CFD or anything, just a user of the Comsol programm. So its likely that i just missed one click or any small boundary condition that has high impact. But still i cant find it.

I really would appreciate any suggestion you can make :)

Thanks in advance.