Divergence ?

[Yvan Fournier]

Hello,

Did you compare that to the flow (for example, if you have a convective loop, it might break symmetry) ?

Regards,

Yvan

[bachlinh]

Hello,

I'm sorry but i don't really understand 'compare that to the flow'.

Regards,

[Yvan Fournier]

Hello,

What I mean is that if the flow field becomes non-symmetric, it may be natural that the temperature field also becomes non-symmetric. This can happen even with symmetric boundary conditions, when the velocity becomes high enough, and a very slight perturbation (such as numerical round-off error or a non-symmetric mesh in a simulation, or a minor vibration in the physical world).

Best regards,

Yvan

[bachlinh]

Hello,

Thank you for your answer.
I compared the the flow field and it is non-symmetric as temperature.
I understand your suggestions about the reason of this behaviour.
But do you have any idea about the manner to find out the main origin (physical or numerical) ?

Best regards,

[Yvan Fournier]

Hello,

I do not know which boundary conditions you used, so whether a higher absorbtion should lead to more or less heat difference between boundaries and more or less natural convection. If convection is stronger, symmetry can be broken more easily.

Is your mesh fully symmetric (by construction) or only symmetric at boundaries (for example generated using an automated triangle or tetrahedral mesher) ?

Regards,

Yvan

[bachlinh]

Hello
The mesh is fully symmetric and uniform.
The configuration is attached below. The obstacle is prescribed at a high temperature and concentration while the lateral walls of the cavity are at the lower values. The ceiling and bottom of the enclosure are adiabatic and impermeable. The absorption coefficient is constant for the whole medium.

Best regards,