use solution of flow equations

Lilly · February 23, 2016, 17:12

Dear all,

I have got a question concerning the solution for the flow equations of a time-periodic transient calculation. I am modelling species transport and want to simulate this transport for about 50 s. However, the velocity pattern is periodic (a cycle has a length of abou 0.7 s). Therefore, I hoped I could save the results of the continuity and Navier-Stokes equations for all elements for one period for each time step and use it at the species transport to save calculation time.
Does somebody know whether this is possible?
Thanks a million for any idea!
Lilly

LuckyTran · February 24, 2016, 02:10

I think it's very hard to do this with Fluent.

Fluent which solves the equation in time domain is not suitable for time-periodic simulations in the first place, this is better handled by a frequency based solver.

The time-periodic condition is not imposed in a time-domain solver, there's no guarantee that your solution is time-periodic in a generalized Navier-Stokes problem.

You would have to save the solution beforehand and then load your solution fields at every time-step. If the fields are not stored directly in RAM but on your hard disk, this read would be very slow. You wouldn't save much time doing it this way.

February 23, 2016, 17:12	use solution of flow equations	#1
Lilly Senior Member Join Date: Feb 2011 Posts: 140 Rep Power: 16	Dear all, I have got a question concerning the solution for the flow equations of a time-periodic transient calculation. I am modelling species transport and want to simulate this transport for about 50 s. However, the velocity pattern is periodic (a cycle has a length of abou 0.7 s). Therefore, I hoped I could save the results of the continuity and Navier-Stokes equations for all elements for one period for each time step and use it at the species transport to save calculation time. Does somebody know whether this is possible? Thanks a million for any idea! Lilly

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February 24, 2016, 02:10		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,845 Rep Power: 68	I think it's very hard to do this with Fluent. Fluent which solves the equation in time domain is not suitable for time-periodic simulations in the first place, this is better handled by a frequency based solver. The time-periodic condition is not imposed in a time-domain solver, there's no guarantee that your solution is time-periodic in a generalized Navier-Stokes problem. You would have to save the solution beforehand and then load your solution fields at every time-step. If the fields are not stored directly in RAM but on your hard disk, this read would be very slow. You wouldn't save much time doing it this way.