[andy.eco]

Dear Fluent Community,

My simulation on Fluent 6.3 is the melting of frost on heated vertical surface.

1) I set up top face as "Pressure inlet", and bottom one as "Pressure outlet".

This setting seems unstable because it got "reverse flow" most of the time. I think the reason for that problem is the distance between two boundaries is too small ( in this case, the distance is 30mm). Therefore, I converted these faces into "Periodic Boundaries" and the model runs better (no reverse flow). However, my control volume is not really a repetitive part of a larger domain, so I would like to ask for your advices on how to set up BCs for this problem.

2) In "Periodic Condition" panel, I set Flow Direction as following: X=0, Y=-1 (Y is also set up for -9.81m/s^2 in Operation condition) and got velocity vector of melted frost pointing upward (?). Can you tell me what wrong with my setting? The pressure gradient is set 0.

3) I set up frost layer as a "fluid" material. On vertical plan, because this fluid volume has no bottom (the bottom now is set as periodic boundary) so I think that the fluid may run down continuously and has non-zero velocity (due to gravity). However, this doesn't happen.

Of course, in reality, frost does stick to the vertical fin surface and drop down only when it is melted til certain amount of it volume. Can you explain why fluid can "stand still" without bottom wall like this?



Thank You for reading and do hope to have your help.


Eco