Some questions about adiabatic wall

*Gasp* · April 12, 2023, 07:39

Hi everyone,

It's been a year since I started using FLUENT, but I still have several questions about the setting of boundary condition.

1st:
Is it correct I set both "heat flux" and "heat transfer coefficient" to 0 if I wanted to keep a wall in adiabatic condition?

2nd:
If I apply a UDF with thermal conductivity(it will change over temperature) to the material of the wall, will it affect the adiabatic condition?

3rd:
According to the question above, If both the UDF and the boundary conditions have an impact, which one has a greater influence during the calculation? Will they both affect the solution or is one more dominant than the other?

Does anyone have any idea?

Thanks for advising.

NickFL · April 12, 2023, 08:44

Are you simulating both the fluid side and the solid side? Or just the fluid side?

1. If you are modeling the fluid side only, you do not need to do anything to have an adiabatic condition. If you are modeling the wall, the heat transfer coefficient will be computed and not an input at the interface of the fluid/solid.

2. The thermal conductivity can be inputted without using a UDF in a number of ways. You can use the piecewise-linear, polynomial or other options. Is there a need to go-to the UDF?

3. The boundary conditions have precedence over the computed solution at the boundary. The thermal conductivity is a material property and therefore will influence your solution inside the domain.

April 12, 2023, 07:39	Some questions about adiabatic wall	#1
Gasp New Member Y. C. Peng Join Date: Mar 2023 Posts: 1 Rep Power: 0	Hi everyone, It's been a year since I started using FLUENT, but I still have several questions about the setting of boundary condition. 1st: Is it correct I set both "heat flux" and "heat transfer coefficient" to 0 if I wanted to keep a wall in adiabatic condition? 2nd: If I apply a UDF with thermal conductivity(it will change over temperature) to the material of the wall, will it affect the adiabatic condition? 3rd: According to the question above, If both the UDF and the boundary conditions have an impact, which one has a greater influence during the calculation? Will they both affect the solution or is one more dominant than the other? Does anyone have any idea? Thanks for advising.

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April 12, 2023, 08:44		#2
NickFL Senior Member Join Date: Jun 2009 Location: Technische Universität Chemnitz Posts: 107 Rep Power: 17	Are you simulating both the fluid side and the solid side? Or just the fluid side? 1. If you are modeling the fluid side only, you do not need to do anything to have an adiabatic condition. If you are modeling the wall, the heat transfer coefficient will be computed and not an input at the interface of the fluid/solid. 2. The thermal conductivity can be inputted without using a UDF in a number of ways. You can use the piecewise-linear, polynomial or other options. Is there a need to go-to the UDF? 3. The boundary conditions have precedence over the computed solution at the boundary. The thermal conductivity is a material property and therefore will influence your solution inside the domain.