Defining insulated/adiabatic sufaces in a transient heat transfer step

[GenericUser]

Hello,

I started using the heat transfer option in CAE the other day. I created a simple 3D bar with a fixed temperature BC at each end (in this case 0 and 150 degrees).

In all the other FEA programs I have used the surface with no loads or boundary conditions is considered to be adiabatic or insulated. I ran a steady state analysis on the model I mentioned and the result was exactly as I expected. The heat flux was constant in the entire bar and the heat was flowing evenly from the 150 degree end to the 0 degree end.

Now I change nothing and I run a transient thermal analysis. It does not matter how long I set the analysis, the temperature never reaches the same result as the steady state analysis. The heat flux is not even, and energy escapes through the surfaces that have no boundary conditions assigned to them. Instead of getting even bands of temperature increasing from the cold side to the hot side, I get a small temperature variation and each end and a very cold center.

So my question is, how does one define an adiabatic or insulated surface in a transient study? I also could not find any option to add an initial temperature.

 

[GenericUser]

Nevermind, I figured it out. I changed the specific heat capacity to very small values and bumped up the conductivity and then the transient solution looked a lot like the steady state one - so I concluded that I needed to bump up the end time for the transient by a factor of 10,000 before the model reaches a steady state.

Also the initial temperature is set by a predefined field in the initial step.

Thanks

GU