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-   -   difference between false and true transient (http://www.cfd-online.com/Forums/main/454-difference-between-false-true-transient.html)

mahesh prakash January 13, 1999 20:41

difference between false and true transient
 
In case of unsteady calculations one often encounters two terms namely : False transient, True transient. As I understand it, a false transient solution does not give the true transient behaviour but gives the correct final steady solution. Are there any other differences between a false transient and true transient solution?

Thanks

John C. Chien January 21, 1999 14:45

Re: difference between false and true transient
 
There are only two types of equations:(1) steady-state equations, and (2) unsteady-state equations. The unsteady-state equations describe the transient behavior of the problem. Sometimes, instead of using the steady-state equations to obtain the steady-state solutions, people have tried to use the unsteady-state equations to obtain the steady-state solution. But, you never know whether this approach will lead you to the steady-state solution or not. And you also have to run the code for a long time in search of the steady-state solution. In the hope to reduce the computing time, some people try to set the time step to be a function of the grid point ( or cell ) in such a way that the time step for that cell can be increased thus the computing time reduced ( if the steady-state solution can be found in this way).


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