|
[Sponsors] |
![]() |
![]() |
#1 |
New Member
Join Date: Oct 2013
Posts: 21
Rep Power: 12 ![]() |
Hello,
in my Oil/Air multiphase flow calculation with a rotating domain (only 1° is modeled) i want to add gravity in the radial direction z. The rotating axes is x. If I set the buoyancy model and use x=0 [m/s^2] y=0 [m/s^2] z=9.81 [m/s^2] the solver automatically counter-rotates the relative Frame gravity vector and so the vector components y and z Change with the Rotation angle. How can i avoid this? Could i use a subdomain and define a momentum source in order to model the gravity? What do i have to add there? The unit is [Nm] best regards Thomas |
|
![]() |
![]() |
![]() |
![]() |
#2 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
Rep Power: 144 ![]() ![]() ![]() ![]() |
If the domain in rotating in the X axis and gravity is along z then I cannot see how a 1° segment with periodic or symmetry conditions can model that. You are going to have to model the full 360°.
But to keep gravity pointing the same direction, you could use a momentum source, or you could just make the gravity vector a function of time. They both sound like they would work. |
|
![]() |
![]() |
![]() |
![]() |
#3 |
New Member
Join Date: Oct 2013
Posts: 21
Rep Power: 12 ![]() |
Hello Glenn,
i think gravity is the wrong word. In my rotational domain (which could be imagined as a rotational couette flow) I get a state where oil droplets are surrounded by air, so they hover in space with no velocity. With the additional body force I want to get them out of the Domain in the radial z direction. I still tried to make the gravity (buoyancy) vector as a function of time but the calculation is not exact because my rotational speed also changes with time. So what I have to add in the momentum source term to apply a Body acceleration in z? regards |
|
![]() |
![]() |
![]() |
![]() |
#4 |
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,816
Rep Power: 144 ![]() ![]() ![]() ![]() |
I do not understand how gravity can be used to help in the strange situation you explain. But I do not need to understand, I will just answer your question
![]() If your rotation changes with time then simply link the rotation of the gravity vector to the rotation speed. Isn't that the easiest approach? I think some tutorials use source terms - not sure which ones, have a look. |
|
![]() |
![]() |
![]() |
![]() |
#5 |
New Member
Join Date: Oct 2013
Posts: 21
Rep Power: 12 ![]() |
Thanks for your help! I will figure it out.
|
|
![]() |
![]() |
![]() |
|
|
![]() |
||||
Thread | Thread Starter | Forum | Replies | Last Post |
rotating domain | mach000 | CFX | 4 | October 24, 2016 02:12 |
Not rotation of free surface in a rotating domain | matte_fole | Main CFD Forum | 0 | October 24, 2012 08:50 |
Counter rotating wall for rotating domain | melvin | CFX | 0 | February 4, 2008 04:51 |
Difference b/t rotating wall and rotating domain? | Juno Kim | CFX | 2 | February 20, 2007 20:08 |
A rotating solid domain in CFX551? | rotlin | CFX | 2 | January 7, 2003 05:59 |