Register Blogs Members List Search Today's Posts Mark Forums Read

 April 22, 2008, 22:26 Quasi-Steady vs. Unsteady #1 Dan Guest   Posts: n/a Could someone give me a explanation of how a quasi-steady solution differs from the unsteady solution? Thanks!

 April 23, 2008, 07:45 Re: Quasi-Steady vs. Unsteady #2 davoche Guest   Posts: n/a From a physical point of view, a quasi steady solution refers to phenomena for which each temporal states of the evolution of your system can be found independantly from a steady state (by applying the same conditions). A contrarion, unsteady phenomena cannot.

 April 23, 2008, 14:08 Re: Quasi-Steady vs. Unsteady #3 Ananda Himansu Guest   Posts: n/a I would say that a non-steady-state flow viewed in a given reference frame is considered quasi-steady if the time-average (over a suitable time scale or period) of the flow quantities at each reference spatial location in the flow is independent of time. This would seem to imply that quasi-steady flows are periodic flows, though I think some authors would include in the quasi-steady category turbulent flows in which the turbulent quantity time-averaged statistics are independent of time. I think what davoche describes is in thermodynamics referred to as quasi-static states of a thermodynamic system.

 April 24, 2008, 04:34 Re: Quasi-Steady vs. Unsteady #4 davoche Guest   Posts: n/a I don't understand how you could obtain a time dependant solution from an time average operation ?

 April 24, 2008, 05:14 Re: Quasi-Steady vs. Unsteady #5 davoche Guest   Posts: n/a Or maybe you think about phase average operation ?

 April 24, 2008, 12:32 Re: Quasi-Steady vs. Unsteady #6 ganesh Guest   Posts: n/a Dear Himanshu, "..........is considered quasi-steady if the time-average (over a suitable time scale or period) of the flow quantities at each reference spatial location in the flow is independent of time". I thought the definition looked more appropriate for stationary flows. A flow is said to be quasi steady if temporal variations at a spatial location are much smaller (they would be zero if the flow was steady) ompared to spatial variations for any quantity. Regards, Ganesh

 April 24, 2008, 14:02 Re: Quasi-Steady vs. Unsteady #7 Ananda Himansu Guest   Posts: n/a That could be so, Ganesh. I was thinking after my post that turbulent flows whose statistics (mean flow and averaged turbulence) were steady would be classified as stationary. Some authors likely do use quasi-steady to mean that the time variations are much smaller than the spatial variations. I was writing from vague memory, but I still believe that some authors refer to periodic flows as quasi-steady.

 April 24, 2008, 14:05 Re: Quasi-Steady vs. Unsteady #8 Ananda Himansu Guest   Posts: n/a Yes, I was referring also to phase-averaging for periodic flows. Because the flow pattern repeats itself periodically, when viewed over one or multiple periods, the flow appears steady, and hence is referred to as quasi-steady. I seem to remember reading about periodic flows being classified as such, though my memory could be deceiving me, and I am too lazy to flip through my textbooks at this time.

 Thread Tools Display Modes Linear Mode

 Posting Rules You may not post new threads You may not post replies You may not post attachments You may not edit your posts BB code is On Smilies are On [IMG] code is On HTML code is OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post elobb FLUENT 3 May 31, 2015 04:11 wlt_1985 FLUENT 6 December 4, 2010 17:17 nico Main CFD Forum 0 September 21, 2007 04:50 prem FLUENT 0 March 30, 2006 10:40 winnie FLUENT 1 April 28, 2003 11:30

All times are GMT -4. The time now is 02:05.