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-   -   How to choose end time for a steady state problem (http://www.cfd-online.com/Forums/openfoam/73350-how-choose-end-time-steady-state-problem.html)

mecbe2002 March 5, 2010 03:46

How to choose end time for a steady state problem
 
Hi,

I am using "rhopSonicFoam" solver for solving 3d steady inviscid flow around ONERA M6 wing. How to decide the end time?

Ma=0.84, alpha=3.04
Properties of air R-287.05 J/kgK, gamma-1.4, T-255.6K

Computational domain size is 11m x 5m x 10m (Hexahedral).
No.of cells = 341797
time step = 5e-07

:confused:

djbungee March 5, 2010 06:54

Hi,

that is an interesting question. My suggestion is that you observe the development of the initial residuals for every equation for the cycles ('time' steps).

If you have sufficient (computation) time and perform this (kind of) simulation or case setup for the first time, I would suggest you do the simulation as long as possible to get an idea of how the residuals develop over computation time (and how low they can go) and try to find a suitable optimum for quality of results (i.e. reduction of change in residual for every cycle - which is not always the same ;)) and computational effort (time).

So, unfortunately, no general guideline available ... :eek:

Best regards, Ulf.

alberto March 25, 2010 22:49

You can additionally track the evolution of which you know the behaviour, and check when it stops evolving.

It is always a good idea to add a "physical" convergence criterion to the one based on residuals.

Best,


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