Hello I am modeling conjugate heat transfer in a channel with thick walls. The fluid is air and solid zone is silicon. The fluid is entering at the 1m/s and 350K. There is no heat flux applied anywhere and all the wall are adiabatic. The solution is initialized with 300K and I expect to get the isothermal temperature distribution in the system but temperature is increasing to 5000K. I think the problem is at the interface between solid and fluid zone. I have coupled the walls at the interface. Can anybody tell what should be the right boundary conditions at the interface?

Vivek

U dont need to define any boundary condition at solid-fluid interface....its just the interface should be coupled and would appear as face and face shadow....well..about temperature...5000K may means ur case didnt converge??? i guess temperature of the fluid at the inlet of teh system is lot less than 5000K

I haven't defined any BC at the interface...energy residual is less than 10^-8 but the temperature keeps increasing till it reaches 5000K. The inlet temperature is 350K....If I change the working fluid from air to water the solution converges....Also if I remove the solid zone and just solve for the fluid zone I get the correct result...but when I am including both solid and fluid it is acting weirdly...I think fluent is not handling the interface properly...Has anybody experienced this problem....

Connect the faces of the solid and the fluid region in GAMBIT itself. The face will automatically assume the BC of coupled wall with a shadow being created. Then try solving the problem in FLUENT.

Regards, Rameche Candane. S

I am using coupled boundary condition...but still I am not getting the correct result...is coupled boundary condition the right BC???

Coupled wall is a BC that is automatically taken when a solid region and fluid region have a common interface. Its a 2 sided wall. I am sure that either you may not have connected the faces of the solid and fluid region properly or u might be having an extra face there. Check the gambit file r reconstruct the mesh file.

Regards, Rameche Candane