topic Transient simulation issue in CFD Forum

Transient simulation issue

Anonymous — Wed, 29 Nov 2017 11:25:55 GMT

Hi,

I am new to transient simulation and i was trying out a very simple geometry consisting of a tunnel with a few flaps on its ceiling (Attached image). I followed some of the analysis setup tips from the help page, but after running the simulation i had to stop the solver as it was taking too much time (4 days) and my file size became a whopping 495GB, Since i wanted to have a smooth animation of the analysis, i put a "save interval" at every 5 steps. But once the simulation is over, it seemed to have none of the iteration results saved except the last one. Could you please suggest what changes can i make to the analysis setup to considerably reduce the simulation time and file size? Also as a next step, i would have to run a motion analysis to simulate wind induced movement in the flaps which are hanging from the tunnel ceiling. Would you suggest a 2D simulation or should I continue working with 3D for a time efficient and acceptable solution? I have attached the .cfz file for your review. Computer configuration is quite good (intel i7-6700K, 64GB RAM). Sorry for bombabrding with so many queries. Your help will be really appreciated!

Best,

Oindrila

Re: Transient simulation issue

Anonymous — Thu, 30 Nov 2017 12:46:29 GMT

Hi @Anonymous,

I suggest you turn off ISC (Intelligent solution control) while doing transient study, since he will overwrite your requested timestep and use its own. I bet he is responsible for the unexpected 4 days calculation. You can also try to save your results according to time instead of steps if you not sure what the solver is doing. Be careful of huge amount of data created in the solver file, you don't want to overfill your HDD. You should determinate prior to launch the analysis how many saved .res file you will have, so you have to know exactly the timestep used by the solver. Which is a hard thing to do when ISC is activated.

Re: Transient simulation issue

matt.bemis — Thu, 30 Nov 2017 19:54:28 GMT

@Anonymous is right here. Depending on the project size, each save interval could be 100 MB - 1+ GB. If each interval is 1 GB and you have 500 save intervals set, you'll fill up your hard drive.

Re: Transient simulation issue

Anonymous — Sat, 02 Dec 2017 08:57:22 GMT

Thanks a lot for the advice @Anonymous as well as @matt.bemis! I will keep that in mind and make the necessary changes.

Best,

Oindrila