Hi all i face whit a problem that it really confused me! i split a face whit an edge and so create 2 zone, one of those is solid and another one is fluid(air) i assign vilocity_inlet to left edge of fluid zone and outflow to right. indeed flow air cross over the solid. i active energy equation and use unsteady condition and K-e. i want to see its cooling after several minutes. but after 20secs i couldn't see any changing in solid zone. i can see thermal boundary layer over solid wall but seem that air can not cool the solid i hope it be enough explanation ,.please tell me : why solid's temperature is constant? k=100 initial temp of solid:500k(i patch solid zone on 500k) velocity inlet :10m/s-300k Whit king regrds Amir

be sure that your faces at interface are connected, so that you can use coupled for boundary conditions

yes otherwise the solid zone will not the the fluid zone and vice versa. They must either share nodes or use a non conformal interface.

Dear red lemon and ritmat i take your advices,but i dont see any changing. Best Amir