Variable Time step for Transient Thermal Analysis

McNickMcNick
Hi,
I tried to search if someone has asked this already, but I want to use variable time steps for a transient thermal analysis.
I am running a multilayer thin film (450um thick), comprising different materials, so the solid element areas are large compared to the thickness (100mm x 100mm x 450um).
I want to start with vary small time steps as the transient analysis begins, as the temperature load of 150 DegC is applied to initial temperature of 20 DegC, with constant convection, giving a discontinuity at the start.
I could refine the mesh at the boundary where the discontinuity occurs, but I would like to see if smaller time steps initially solve the issue, and then go for larger time steps once the transient has passed.
Is this possible as a Control Code in CCX ?

Comments

  • FatmacFatmac
    If u are using NL then by setting the time period to 1s
    there are some easy options to manipulate the time steps. Here I have shown a n an option Also by using tabular input a series of steps can be introduced

  • McNickMcNick
    Thanks. I have tried to ramp the temperature load over time, and the errors decrease as the time step and ramp decrease.
    Is it possible to have very small time steps for part of the solution, and then to increase the time step once the very non-linear temperature transient has passed ?
  • FatmacFatmac
    I may have not properly understood ur question correctly but i think there are several ways to achieve what u are after. The simple way is to use tabular inputs. If u run the analysis over say 20 seconds and u expect the tricky nonlinear part to be only in the first 5 then something like in this screen shot would do Also if u have automatic time stepping selected the time steps will naturally be smaller where the
    going gets tough
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