[vidyadhar]

Dear All,

I am beginner and using openFOAM.

I am using Transient solver. How to verify whether the simulation has reached steady state. Do we have to check the changes in properties at all spatial locations or do we have to take averaging.

Or, Is there any other way to do this?

[Arya_the_Rabbit]

Originally Posted by vidyadhar

Dear All,

I am beginner and using openFOAM.

I am using Transient solver. How to verify whether the simulation has reached steady state. Do we have to check the changes in properties at all spatial locations or do we have to take averaging.

Or, Is there any other way to do this?

Hi vidyadhar,
precisely a transient solution never reach a steady state for the intrinsic behaviour of an unsteady flow. In order to know when a solution has gone to convergence you have to simply monitor your residual and your physical quantities of interest (i.e. drag coefficient). In a transient solution you will have always an oscillating solution, therefore you need to average the last N step.
Remember to average only the last steps of your simulation, where the solution oscillates steadily in a certain limit (sign that you reach convergence).

[FMDenaro]

I think that the question is about the transient for a case that admits a steady solution. That requires to check the time derivatives of the variables that are solved, they must go below a certain threshold.

[vidyadhar]

Hello Arya & Filippo Maria Denaro,Thank youfor the suggestions.

Also, can you please let me know how to quantify the periodic/unsteady flow.

I am thinking of taking velocity time history at certain locations.


Thanks & Regards,
vidyadhar

[Brock17]

I'm not entirely sure what you mean by 'quantifying' the periodic flow?

From my interpretation, you can find the frequency by plotting an instantaneous value (such as lift coefficient) over time. Once the flow has fully developed this graph should oscillate and you can find the frequency from the time period of the resultant wave.