# is it necessary to d ofirst steady analysis ?

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 January 21, 2006, 12:28 is it necessary to d ofirst steady analysis ? #1 ravi Guest   Posts: n/a Is it necessary to first do a steady state analysis and from that conserved results as a intial files to do a transient analysis in fluent?

 January 21, 2006, 17:37 Re: is it necessary to d ofirst steady analysis ? #2 Ahmed Guest   Posts: n/a Not always

 January 22, 2006, 07:37 Re: is it necessary to d ofirst steady analysis ? #4 ravi Guest   Posts: n/a Thanks sir.

 January 23, 2006, 04:15 Re: is it necessary to d ofirst steady analysis ? #5 Luca Guest   Posts: n/a To me it is senseless to study a problem without getting a steady solution before transient analysis. This is because your system response depends on the (initial) status of your NON-LINEAR system. What you do is then study how your system responds to an excitation signal. Depending of the initial status you'll get a different response. When the transient is over you'll get an another steady-value (depending of what kind of excitation you used). Luca

 January 23, 2006, 04:35 Re: is it necessary to d ofirst steady analysis ? #6 kharicha Guest   Posts: n/a to Luca, You have come to the point!! You are right if the system is highly non-linear, i.e chaotic, i.e strong dependance on the initial conditions. And before studying a non-linear regime, we should verify first that our model (grid,equations, discretization of the convectif term..) is able to cath the frequencies occuring in the linear regime. And before that it is necessary to perform a steady state analizis.... Strictly speaking, the transient evolution of the system depends on the perturbations introduced added to the steady solution. But unfortunatly, I know a lot of people that try to model chaotic system without the necessary care. This is either due to a lake of knowledge or a lake of time....

 January 23, 2006, 06:49 Re: is it necessary to d ofirst steady analysis ? #7 Luca Guest   Posts: n/a I agree with you. Luca

 January 27, 2006, 10:28 Re: is it necessary to d ofirst steady analysis ? #8 Marie-Anne Guest   Posts: n/a Hi, I read your comments and have a question arising from this even though I agree mostly with what you say. I medelize the onset of natural convection in a chemney. Therefore, if I run a steady state analysis and apply the result as initial conditions to the transient one, the convection is already happening and I cannot see the onset. How do I get to verify my transient computations with no steady state initiation ? Thank you, Marie Anne

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