Negligible Inertia and Convective Heat Transfer

Miky1020 · June 9, 2009, 16:17

Hi,

I'm simulating two-phase flow dominated by capillary forces, so inertia and convective heat transfer are negligible. Follow to CFX documentation, CFX solves conservation equations with full terms, I mean, inertia for momentum and convective terms for energy. Is it possible to solve the equations without those terms? how can I do it? Maybe editing CCL?

Thanks.

Miguel Baritto

ghorrocks · June 9, 2009, 19:36

Hi,

No, it is not possible to ignore these terms. Here's some ideas:

Rather than use temperature if you use a user scalar you can choose to not include convection. If there is any coupling between temperature and the flow this will make it trickier though.

We put in a feature request for this exact model about 12 months ago and the developers did not take kindly to it. They said that few people wanted the feature and it could be modelled with the full equations anyway. It is true that low Re number flow usually converges very quickly even with the insignificant terms included but it means the solver is wasting lots of time and memory evaluating terms of no importance.

We now often use Gerris for this type of work. It is open source and you do the sort of simplifications you talk about. Gerris is quite limited in its capabilities but it may be of use. Worth a look.

Glenn Horrocks

Miky1020 · June 9, 2009, 21:16

Hi Glenn, thanks a lot for your reply, again. I'll take a look Gerris.

June 9, 2009, 16:17	Negligible Inertia and Convective Heat Transfer	#1
Miky1020 New Member Miguel Baritto Join Date: Mar 2009 Location: Caracas,Venezuela Posts: 16 Rep Power: 17	Hi, I'm simulating two-phase flow dominated by capillary forces, so inertia and convective heat transfer are negligible. Follow to CFX documentation, CFX solves conservation equations with full terms, I mean, inertia for momentum and convective terms for energy. Is it possible to solve the equations without those terms? how can I do it? Maybe editing CCL? Thanks. Miguel Baritto

June 9, 2009, 19:36		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,872 Rep Power: 144	Hi, No, it is not possible to ignore these terms. Here's some ideas: Rather than use temperature if you use a user scalar you can choose to not include convection. If there is any coupling between temperature and the flow this will make it trickier though. We put in a feature request for this exact model about 12 months ago and the developers did not take kindly to it. They said that few people wanted the feature and it could be modelled with the full equations anyway. It is true that low Re number flow usually converges very quickly even with the insignificant terms included but it means the solver is wasting lots of time and memory evaluating terms of no importance. We now often use Gerris for this type of work. It is open source and you do the sort of simplifications you talk about. Gerris is quite limited in its capabilities but it may be of use. Worth a look. Glenn Horrocks

June 9, 2009, 21:16		#3
Miky1020 New Member Miguel Baritto Join Date: Mar 2009 Location: Caracas,Venezuela Posts: 16 Rep Power: 17	Hi Glenn, thanks a lot for your reply, again. I'll take a look Gerris.