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Steve March 24, 2008 16:32

Time accurate?

Could someone please explain what the term "time accurate" means? I'm new to CFD and have been reading some textbooks on finite difference methods. I have many times read a program described as time accurate but don't know what this means.

I wondered if time accurate means that the program is accurate in time but that doesn't make much sense. Surely a program that isn't good in time would simply be wrong? I don't see the meaning of specifically saying that the program is time accurate.


ag March 25, 2008 08:55

Re: Time accurate?
Consider that many times a problem of interest has a solution that is steady or unchanging in time. In this case it can be more efficient to solve the fluid equations that describe the steady-state behavior. The steady equations are a subset of the full NS equations. Of course, one can also reach the same solution (in theory) by solving the full NS equations that contain all the dynamic (transient) terms. Solvers that only solve the steady equations are not time-accurate, but they may do an excellent job on problems where time accuracy is not required (i.e. flow over an airfoil at low angle of attack, flow through a nozzle, etc.) Solvers that can provide solutions to the full unsteady equations are referred to as time-accurate solvers. They come into play when the problem of interest requires an unsteady solution.

Steve March 25, 2008 09:39

Re: Time accurate?
Thank you ag. This is a good explanation.


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