Learning Forum

[alemore]

Hi everyone, I am trying to do a transient thermal analysis of a joint consisting of three parts each having different material properties. I am considering convection with bulk fluid temperature at the joint internal and convection with room temperature at the external surface. I read online that time step of transient thermal analysis is determined by using Biot and Fourier Numbers as shown in the attached picture.

[Aniket]

You should check it visually in the direction of the heat flow, or define sizing on the body so that sizing is forced.
calculate using all materials and use the largest timestep that you get as the minimum timestep for your analysis.
I believe it should be the external one.
Please search for "Transient Thermal Analysis in Ansys Mechanical Workbench: Dealing with Non-Physical Temperature Results" for some more details.
The basic idea here is to keep minimum timestep in your model large to avoid getting non physical result, if you want minimum time step to be smaller, you will have to refine your mesh further to be able to use it.
-Aniket
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