Defining Planetary Motion

Sreyas14 · June 22, 2016, 07:39

Hello everyone,

I have been facing a problem in defining the rotation of a body in CFX.
I want to define a planetary motion to a body (a body rotating at a fixed radius from the center, the body can be larger than the radius of rotation). I don't find any option to define such a motion in CFX.

I tried defining its rotation under the domain tab in the setup page. Domain Models -> Option -> Rotating. However I'm getting a purely rotating motion about the center.

I do not want the object to be changing its orientation. I just want it to move in a circular path.

Please help me with this, thank you!

ghorrocks · June 22, 2016, 08:17

Define the body in a rotating frame of reference (where the rotation axis is not necessarily through the body), and set the wall boundaries on the body to counter-rotating.

Sreyas14 · June 24, 2016, 02:26

I have a stationary body as well, alongside the body in planetary motion. Also I can't set the wall to be rotating, as the enclosure is like a water tank, with outlet on the wall.

ghorrocks · June 24, 2016, 06:31

Can you post an image of what you are modelling and describe what is happening and where?

Sreyas14 · June 24, 2016, 06:47

Sure, PFA

Top View.png

Iso View.png

There are two scrolls, one rotating and one stationary. The inlet to the gas (smaller radius) is at the top and outlet (larger radius) is on the side wall of the enclosures.

Alternately, check out this YouTube video, to understand the kind of rotation I'm trying to achieve.
https://www.youtube.com/watch?v=iU5PVinDyNQ

Thanks a lot for your help!

ghorrocks · June 24, 2016, 06:52

I can only see two choices to model this motion: immersed solids or dynamic remeshing. You cannot model this by rotating frames of reference.

Sreyas14 · June 25, 2016, 09:14

Thanks once again.

Could you provide with any links of tutorials of dynamic meshing.

A lot of content is on dynamic meshing in ANSYS Fluent, but I am not able to find any good resource/tutorial for ANSYS CFX dynamic meshing.

ghorrocks · June 25, 2016, 20:55

The immersed solid approach is MUCH easier and I recommend you try that before you go for dynamic remeshing.

I think the dynamic remeshing tutorials are on the ANSYS community webpage.

June 22, 2016, 07:39	Defining Planetary Motion	#1
Sreyas14 New Member Arun Sreyas Join Date: Jun 2016 Posts: 4 Rep Power: 9	Hello everyone, I have been facing a problem in defining the rotation of a body in CFX. I want to define a planetary motion to a body (a body rotating at a fixed radius from the center, the body can be larger than the radius of rotation). I don't find any option to define such a motion in CFX. I tried defining its rotation under the domain tab in the setup page. Domain Models -> Option -> Rotating. However I'm getting a purely rotating motion about the center. I do not want the object to be changing its orientation. I just want it to move in a circular path. Please help me with this, thank you!

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June 22, 2016, 08:17		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Define the body in a rotating frame of reference (where the rotation axis is not necessarily through the body), and set the wall boundaries on the body to counter-rotating.

June 24, 2016, 02:26		#3
Sreyas14 New Member Arun Sreyas Join Date: Jun 2016 Posts: 4 Rep Power: 9	I have a stationary body as well, alongside the body in planetary motion. Also I can't set the wall to be rotating, as the enclosure is like a water tank, with outlet on the wall.

June 24, 2016, 06:31		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Can you post an image of what you are modelling and describe what is happening and where?

June 24, 2016, 06:47		#5
Sreyas14 New Member Arun Sreyas Join Date: Jun 2016 Posts: 4 Rep Power: 9	Sure, PFA Top View.png Iso View.png There are two scrolls, one rotating and one stationary. The inlet to the gas (smaller radius) is at the top and outlet (larger radius) is on the side wall of the enclosures. Alternately, check out this YouTube video, to understand the kind of rotation I'm trying to achieve. https://www.youtube.com/watch?v=iU5PVinDyNQ Thanks a lot for your help!

June 24, 2016, 06:52		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	I can only see two choices to model this motion: immersed solids or dynamic remeshing. You cannot model this by rotating frames of reference.

June 25, 2016, 09:14		#7
Sreyas14 New Member Arun Sreyas Join Date: Jun 2016 Posts: 4 Rep Power: 9	Thanks once again. Could you provide with any links of tutorials of dynamic meshing. A lot of content is on dynamic meshing in ANSYS Fluent, but I am not able to find any good resource/tutorial for ANSYS CFX dynamic meshing.

June 25, 2016, 20:55		#8
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The immersed solid approach is MUCH easier and I recommend you try that before you go for dynamic remeshing. I think the dynamic remeshing tutorials are on the ANSYS community webpage.