Problem Interface Solid Fluid with wall velocity Solver v12

hills1 · October 9, 2009, 09:26

Hi,

i ve a problem modelling an interface between a solid and a fluid part with solver v12. The solid part is a rotating shaft so it has some wall velocity. I model the connection as a GGI, and set a wall velocity for the Interface Fluid Shaft, at the fluid side.
If i ve a look at the wall velocity in Post it has some strange behaviour. The wall velocity has some rough jumps along the shaft, from the correct wall velocity to zero wall velocity at areas where the fluid mesh is quite fine. The corresponding solid mesh is much coarser then, but anyway i can not model it as fine as the fluid. So i guess there is s.th. wrong with the interface, but i am not sure. I ran this calculation with v12 solver. I ran the same definition file with v11 and did the same plot. With version 11 the wall velocity is correct, with version 12 it is wrong.
For solver v11 "expert parameter"-> "ggi bitmap resolution" is set to 7.
For solver v12 the parameter is not changed, but it has another name in v12. It is "Solver control" -> "Intersection control" -> "Bitmap resolution=7"
Any ideas how i can solve it?

Regards

ghorrocks · October 10, 2009, 06:05

I seem to remember that rotation for solid domains is a new feature in V12. It would not surprise me if it has not been tested as thoroughly as it could be - keep in mind you may have found a bug in CFX. If determine that your problem is a bug then please report it to CFX support so it can get fixed.

What velocity are you looking at? Conservative or hybrid?

The wall velocity might be right in V11 but I suspect the behaviour inside the rotating component is not as rotating solid domains was nto supported before V12 (I think, not 100% sure).

hills1 · October 12, 2009, 05:36

Hi,

it doesnt matter if i look at Hybrid or Conservative values, the drop to zero wall velocity is the same in both cases :/
I just loaded the definition file of v11 in v12 and set a rotational velocity for the solid. Still there is the drop :/
So i think there is a problem with Solver v12...I ll ask the support about it.

Regards

October 9, 2009, 09:26	Problem Interface Solid Fluid with wall velocity Solver v12	#1
hills1 New Member Join Date: Oct 2009 Posts: 2 Rep Power: 0	Hi, i ve a problem modelling an interface between a solid and a fluid part with solver v12. The solid part is a rotating shaft so it has some wall velocity. I model the connection as a GGI, and set a wall velocity for the Interface Fluid Shaft, at the fluid side. If i ve a look at the wall velocity in Post it has some strange behaviour. The wall velocity has some rough jumps along the shaft, from the correct wall velocity to zero wall velocity at areas where the fluid mesh is quite fine. The corresponding solid mesh is much coarser then, but anyway i can not model it as fine as the fluid. So i guess there is s.th. wrong with the interface, but i am not sure. I ran this calculation with v12 solver. I ran the same definition file with v11 and did the same plot. With version 11 the wall velocity is correct, with version 12 it is wrong. For solver v11 "expert parameter"-> "ggi bitmap resolution" is set to 7. For solver v12 the parameter is not changed, but it has another name in v12. It is "Solver control" -> "Intersection control" -> "Bitmap resolution=7" Any ideas how i can solve it? Regards Last edited by hills1; October 9, 2009 at 10:11.

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October 10, 2009, 06:05		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,696 Rep Power: 143	I seem to remember that rotation for solid domains is a new feature in V12. It would not surprise me if it has not been tested as thoroughly as it could be - keep in mind you may have found a bug in CFX. If determine that your problem is a bug then please report it to CFX support so it can get fixed. What velocity are you looking at? Conservative or hybrid? The wall velocity might be right in V11 but I suspect the behaviour inside the rotating component is not as rotating solid domains was nto supported before V12 (I think, not 100% sure).

October 12, 2009, 05:36		#3
hills1 New Member Join Date: Oct 2009 Posts: 2 Rep Power: 0	Hi, it doesnt matter if i look at Hybrid or Conservative values, the drop to zero wall velocity is the same in both cases :/ I just loaded the definition file of v11 in v12 and set a rotational velocity for the solid. Still there is the drop :/ So i think there is a problem with Solver v12...I ll ask the support about it. Regards