Questions about rotate immersed solid and mesh deformation

wjy-c · June 15, 2013, 11:57

Hi, I’m trying to simulate water splash in box baused by gear rotating. I’m new to CFX and I have tried several times, but the results turn out that the water volume fraction is no right., so I will be appreciated for your help.
(1) I read the CFX help document, I noticed that the immersed solid would not interact properly with mutiphase fluid. Since I concerned about the water and airdistribution caused by rotating gear, does the help document means I cannot use immersed solid for my simulation?
(2) I try a gear in a box model and the simulation result seems correct. But I did not define mesh deformation, I’m wondering wether or not the meshdeformation must be defined in situation like mine, I suppose the mesh deformation is required, but how to explain my successful simulatin in the first time.
P.S.
English is not my native language, so I may understand and express mistakely , so please corret me if I made some mistake. Thank you very much!

ghorrocks · June 16, 2013, 07:34

The documentation states that immersed solids do not interact properly with multiphase flow. I do not thing immersed solids is a good way to do this simulation. If the gear rotates then you might be able to do it with a rotating frame of reference. This is quite easy and fully supports multiphase flows. Note you do not need mesh deformation for this approach - which is a big help as it complicates the simulation a lot.

wjy-c · June 17, 2013, 08:56

thank you for your reply. my friend recently told me that I could creat a rotating multiphase domain which contain the gear and regard the rotating gear as wall boundary. I figure conduct my simulation successfully as my friend's advice. consider the rotating frame of refernce as you mentioned, I do not quite understand what does the "reference" mean, do you mean the same solution as my friend said?

ghorrocks · June 17, 2013, 09:11

You have to be very careful to use the correct words. Some of the features in CFX have similar names but are quite different. So be very careful to use the correct name for the CFX features you are talking about.

The rotating domains of reference model is mainly used for turbomachinery modelling, but is useful for just about anything else which rotates as well. It is valid with just about all the physics models so you can use complex multiphase models with it.

You might be able to do this with moving mesh but it will be much more complex and slower.

You might be able to do this with a rigid body solver but it will be much more complex.

I do not think you can do this with an immersed solid approach as it does not properly support multiphase.

wjy-c · June 17, 2013, 12:33

It's very kind of you to offer me those advices. I understand what you mean. Really thank you.

June 15, 2013, 11:57	Questions about rotate immersed solid and mesh deformation	#1
wjy-c New Member Jingyao Wang Join Date: Jun 2013 Posts: 29 Rep Power: 13	Hi, I’m trying to simulate water splash in box baused by gear rotating. I’m new to CFX and I have tried several times, but the results turn out that the water volume fraction is no right., so I will be appreciated for your help. (1) I read the CFX help document, I noticed that the immersed solid would not interact properly with mutiphase fluid. Since I concerned about the water and airdistribution caused by rotating gear, does the help document means I cannot use immersed solid for my simulation? (2) I try a gear in a box model and the simulation result seems correct. But I did not define mesh deformation, I’m wondering wether or not the meshdeformation must be defined in situation like mine, I suppose the mesh deformation is required, but how to explain my successful simulatin in the first time. P.S. English is not my native language, so I may understand and express mistakely , so please corret me if I made some mistake. Thank you very much!

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Two-sided Wall Heat Transfer BC - No Separate Solid Mesh and No Heat Transfer Coeff	swahono	OpenFOAM Running, Solving & CFD	10	October 15, 2018 06:43
Flow over a flat plate as an immersed solid	hamed.majeed	CFX	4	September 8, 2016 15:40
[snappyHexMesh] SnappyHexMesh for internal Flow	vishwa	OpenFOAM Meshing & Mesh Conversion	24	June 27, 2016 09:54
Update of the variables after dynamic mesh motion.	gtg258f	OpenFOAM Programming & Development	9	January 18, 2014 11:08
Error finding variable "THERMX"	sunilpatil	CFX	8	April 26, 2013 08:00

June 16, 2013, 07:34		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	The documentation states that immersed solids do not interact properly with multiphase flow. I do not thing immersed solids is a good way to do this simulation. If the gear rotates then you might be able to do it with a rotating frame of reference. This is quite easy and fully supports multiphase flows. Note you do not need mesh deformation for this approach - which is a big help as it complicates the simulation a lot.

June 17, 2013, 08:56		#3
wjy-c New Member Jingyao Wang Join Date: Jun 2013 Posts: 29 Rep Power: 13	thank you for your reply. my friend recently told me that I could creat a rotating multiphase domain which contain the gear and regard the rotating gear as wall boundary. I figure conduct my simulation successfully as my friend's advice. consider the rotating frame of refernce as you mentioned, I do not quite understand what does the "reference" mean, do you mean the same solution as my friend said?

June 17, 2013, 09:11		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,852 Rep Power: 144	You have to be very careful to use the correct words. Some of the features in CFX have similar names but are quite different. So be very careful to use the correct name for the CFX features you are talking about. The rotating domains of reference model is mainly used for turbomachinery modelling, but is useful for just about anything else which rotates as well. It is valid with just about all the physics models so you can use complex multiphase models with it. You might be able to do this with moving mesh but it will be much more complex and slower. You might be able to do this with a rigid body solver but it will be much more complex. I do not think you can do this with an immersed solid approach as it does not properly support multiphase.

June 17, 2013, 12:33		#5
wjy-c New Member Jingyao Wang Join Date: Jun 2013 Posts: 29 Rep Power: 13	It's very kind of you to offer me those advices. I understand what you mean. Really thank you.