# Time-Accurate Simulation

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 February 22, 2005, 10:36 Time-Accurate Simulation #1 John Guest   Posts: n/a I am looking for a good explanation of "Time-Accurate Simulation", what is it and how can it be applied? If anybody knows it, or knows where I can find it, please let me know. Thanks.

 February 22, 2005, 14:17 Re: Time-Accurate Simulation #2 Runge_Kutta Guest   Posts: n/a Time accurate means the time step is chosen to correspond to the fastest physically relevant time scales. This means you are tracking the solution closely as it evolves in time. It makes consummate sense when there are dynamic things going on in the flowfield.

 February 23, 2005, 03:54 Re: Time-Accurate Simulation #3 Rami Guest   Posts: n/a In many CFD simulations, only steady-state solution is sought. In such cases, a common approach is to use a pseudo-time approach, in which the solution is iterated by advancing it in time as in transient flow, BUT the time-step in each cell is different and based on the local stability criteria in each cell. This allows a faster convergence to steady state but the physical meaning of this "time" is lost, i.e., at any intermediate iteration, the solution is NOT a valid transient solution of the problem - it is merely another iterative approximation to the final steady solution. On the other hand, when the same time step is used throught the grid (in which case it is the minimal local time step in all cells) then the physical significance of time is retained. This latter approach is commonly termed "time-accurate".

 February 24, 2005, 10:50 Re: Time-Accurate Simulation #4 John Guest   Posts: n/a Thanks to both of you. Was very helpful. Do you know any reference for more info on this issue? Please let me know if there is any. Thanks!

 February 24, 2005, 11:03 Re: Time-Accurate Simulation #5 Rami Guest   Posts: n/a Look for papers on Jameson et al from the early 80's. One of these is A. Jameson, W. Schmidt and E. Turkel, Numerical Solutions of the Euler Equations by a Finite Volume Method using Runge-Kutta Time-Stepping Schemes, AIAA paper 81-1259, 1981. The above must have also been published in a journal (probably one of AIAA) at about the same year.

 February 24, 2005, 23:51 Re: Time-Accurate Simulation #6 amol palekar Guest   Posts: n/a Time accurate simulation also implies that convergence is achieved at each time step and not only at final time step. amol

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