No heat transfer in transient simulation (Fluent)
 

Hi, I am new to Fluent and I am running a transient simulation for a rotating disc rotor. I noticed that if I run a transient simulation by using the steady state result as the initial condition, the conduction on solid disc will occur and the temperature on my disc will keep changing with time. But, if I directly run the transient without steady state initial condition, the temperature will not change and no heat transfer can be observed. Can anyone help explain that? Thanks