[oozcan]

what should be boundary condition that is open to atmosphere in control volume?

Pressure outlet or symmetry,

That is why I ask, I have seen a case made as symmetry.

[sina_mech]

symmetry as outlet?! I would say, maybe in those cases they used it as periodic boundary.

[oozcan]

Originally Posted by sina_mech

symmetry as outlet?! I would say, maybe in those cases they used it as periodic boundary.

Radial direction in enclosure was symmetry in electric motor model I have seen today.

Periodic boundary is recurrent model ?

the thing I have asked is what boundary condition is defined in those enclosures,control volume ?

Kind Regards,

[Antanas]

Symmetry BC means: d(phi)/dn = 0, Un = 0, where phi - any variable, Un - normal velocity. Obviously there cannot be fluid flow through symmetry.

[oozcan]

Originally Posted by Antanas

Symmetry BC means: d(phi)/dn = 0, Un = 0, where phi - any variable, Un - normal velocity. Obviously there cannot be fluid flow through symmetry.

Model is attached. As you can see,outlet is very near to solid one. (that is my thought, maybe it is wrong approximation). How does boundaries in model be near to interest ? and what kind of boundary condition should be define it in model boundary ? all boundaries are imaginary. Because the model is control volume

[Antanas]

Originally Posted by oozcan

Model is attached. As you can see,outlet is very near to solid one. (that is my thought, maybe it is wrong approximation). How does boundaries in model be near to interest ? and what kind of boundary condition should be define it in model boundary ? all boundaries are imaginary. Because the model is control volume

Strange question. You should decide which BC is correct in your case. If boundaries of your domain are close to your region of interest, then you should set BC accurately, because they may influence solution in the region of interest. If you don't know exact conditions at current boundaries, then move 'em away from region of interest, so that error in BC posing don't influence solution in the region. Maybe it was the case in the example you montioned. They just made boundaries far away flom object and set symmetry there to make fluid flow parallel to boundaries.

[oozcan]

Originally Posted by Antanas

Strange question. You should decide which BC is correct in your case. If boundaries of your domain are close to your region of interest, then you should set BC accurately, because they may influence solution in the region of interest. If you don't know exact conditions at current boundaries, then move 'em away from region of interest, so that error in BC posing don't influence solution in the region. Maybe it was the case in the example you montioned. They just made boundaries far away flom object and set symmetry there to make fluid flow parallel to boundaries.

The thing is of interest that solid material temperature distribution. Red coloured fluid that is not flowing and heats the solid material. air having high velocity is to cool the solid material from external.

So, as for model that I have defined , air (cooling air) is to define all imaginary boundaries (control volume). I take into condesiration on a solid material being heated via heat transfer and cooled by air.Which direction does the model be extended ? Actually I could not take into consideration air flow behaviour following cooling the material. I could say that I pay no attention how swirls or eddies are damped in symmetry boundary condition