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 wawa November 9, 2010 13:45

Hi Everybody,

I am trying to figure out how to determine that a transient simulation is actually reaching steady state.
I understand that in a steady state simulation, if the solution converged, a steady state solution is reached. However, in transient simulations, a converged solution implies that a solution for the time step is reached. But how do we know whether the solution is steady state ?

Thanks ...

 simulationman November 9, 2010 15:35

Well, if your problem has a steady state and if each of your time steps are converging, then you should reach a steady state after certain number of time steps.

Now there can be many ways to determine what a steady state is. The idea is that you need to define a criteria to determine a steady state. Say for example, you can say that if the change in velocity is less than 0.1% in 10 time steps, you will consider that a steady state is reached.

So basically you need to define a criteria for steady state ( or a norm for determining when a steady state is reached).

Now depending upon your exact need you will have to work on the complexity of the criteria. But in general, as a first step, you can just see the output at different time steps and just visually call it a steady state when you find that the solution is not changing appreciable with time.

 wawa November 9, 2010 18:44

Hi simulationman,