
Re: Steady state vs. time depended analysis
Chris Michalski Jun 19, 2012 4:22 PM (in response to Shahar Dor Zidon)the definition of steady state is that the simulation will reach one continuous state (temperatures, velocities, pressures, etc. will reach a steady state).
For example, flow around a tube can continually oscillate downstream of the tube. This type of simulation may never reach a steady state (depending on boundary conditions).
For a time dependent simulation Flow Simulation saves each time step of information so you can look at the results as a function of time.
For steady state it saves the final converged answer as this is the "steady state" solution.

Re: Steady state vs. time depended analysis
Keith Vittitoe Jun 19, 2012 4:33 PM (in response to Shahar Dor Zidon)Shahar,
Hello. Steady state in flow is the same as a textbook definition. The flow solver assumes every study is a transient analysis, so for steady state analysis (not timedependent), it will look for convergence or run until it times out (if that is specified).
Use the Timedependent setting for transient analysis and let flow find steady state otherwise.
Best Regards,
Keith

Re: Steady state vs. time depended analysis
Bill McEachern Jun 19, 2012 4:38 PM (in response to Shahar Dor Zidon)A little more subtelty maybe required: It is fluid dynamics we are concerned with here so in the strict sense there is no such thing as "steady state"  that would be fluid statics. It would be slightly more precise to call it quasi steady state  there will always be fluctuations in the flow in the B'layers and little eddys hera and there that are time varing. Steady state inthe context of flow sim is achieve the more or less steady conditions that results after the initial start up transients have been resolved. YOu cna get a steady state analysis where you have goals that will not be steady becuase real flow fluctuations are occuring  say eddies shedding off an obstruction ala a Karmen votex street. where you have a goal of the pressure on the surface and it fluctuates. A steady state analysis in flow sim is a transient analysis where time is not tracked explicitly and it only saves the last result.

Re: Steady state vs. time depended analysis
Shahar Dor Zidon Jun 19, 2012 4:42 PM (in response to Bill McEachern)wowww Guys that was quick :)
Thanks
Just to verify
If I’m running an analysis without checking the time depended & define time for the analysis the simulation result will reflect the situation when there is no more changes in the flow characters (pressure, temp, velocities…)
?

Re: Steady state vs. time depended analysis
Chris Michalski Jun 19, 2012 4:45 PM (in response to Shahar Dor Zidon)it will stop when the goals are met. If you do not create goals, then it will run the maximum number of iterations specified in the calculation control options.
What you normally do is set goals for the variables you are interested in making sure have stabilized. i.e. minimum pressure, maximum velocity, average temperature of a given component, etc.

