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 The_Architect February 18, 2013 10:15

Initial value to accelerate a simulation

Hello,

I'm working with a project where we're trying to figure out how much an "appropriate" initial value would save computational effort during a simulation. We will run simulations under different conditions. However, I find it hard to find any literature about the topic. Does anybody have an idea where I could read about the effect the initial value has on the convergence of a simulation?

Thank you!

 andy_ February 18, 2013 11:32

Quote:
 Originally Posted by The_Architect (Post 408461) I'm working with a project where we're trying to figure out how much an "appropriate" initial value would save computational effort during a simulation. We will run simulations under different conditions. However, I find it hard to find any literature about the topic. Does anybody have an idea where I could read about the effect the initial value has on the convergence of a simulation?
Are these steady-state or time accurate simulations?

The broad answer is not much so long as you avoid a big bang. I don't think it is much of an academic topic but more practical knowledge one tends to pick up after doing a few CFD simulations. If your flow is prone to big bangs (e.g. aggressively diffusing flows) then turning on the inlet steadily over a few steps rather than instantly can help quite a lot, as can starting from a previous solution or, for transient flows, imposing a tight tolerance for mass conservation on the first iteration to get the flow moving everywhere although this can sometimes backfire if the generated flow is grossly unrealistic and takes a long time to blow out the exit.

 The_Architect February 22, 2013 06:56