Reply To: modeling heat transfer considering thin wall separating two fluids

[Rob]

A wall without a shadow only has cells on one side, so the grey and blue surfaces, if external, would be wall with no shadow. Change one of the fluids to solid (you will have to turn off flow boundaries) and see if any walls form or you see any warnings. I'd be surprised if the wall & shadow switched anywhere, but if you have isolated regions it could be correct.