Classical modeling of a partially filled rotating container

cassini83 · July 23, 2015, 14:58

Hello friends,

I am in the process of setting up an CFX simulation to model the classical example of a partially filled rotating vertical container. The fluids are water and air, with an opening on top of the vessel. I would like to share my approach and get your feedback accordingly.

The goal is to model the parabolic shape of the water surface as a function of angular velocity.

The parabolic shape can be calculated analytically by using the following equation:

z(r) = omega^2*r^2/2g (2D)

It is evident that this is a free surface flow problem. Assuming that the mesh is adequate enough, my approach is to define a fluid volume that's partially water and air, using CEL expressions as advised by section 7.18.5 of the VT manual (VOF approach). this will allow me to have consistent pressure field and volume fraction conditions.

Manual: http://www.arc.vt.edu/ansys_help/cfx_mod/i1306346.html

Both fluids will be continuous, and I will impose a rotating domain with omega = 500 rpm.

An opening boundary condition with VOF air = 1, and VOF water = 0, and 1 atm reference pressre will be created.

Omitting the rest of the steps, I would like to stop here and see if anybody has done this simulation in CFX in a similar fashion. Are there any other approaches recommended? (Such as, starting with solid domain of the container, or creating subdomains for each fluid, etc).

By the way, this would be a 3D simulation. Steady state.

I am getting results (CFD-POST) but they are not what I am expecting. I am not getting any errors during the solving period. Also, when I viewed the results in terms of volume fraction for each fluid, I can see an interface and the water level is at the right height. However, it looks like the rotational condition is not being set correctly.

I will post some more details about my setup as soon as possible, including some pictures.

Anything you can add in the meantime would be great.

Thanks!

Martin_Sz · July 23, 2015, 17:34

This is a big problem to make solution of domains of air and water and one of them rotating. Immersed solid is not solution for your modelling

ghorrocks · July 23, 2015, 19:38

What are you seeing? You will need to post some images of what you are getting, your mesh and your CCL.

July 23, 2015, 14:58	Classical modeling of a partially filled rotating container	#1
cassini83 New Member Alberto Join Date: Jun 2014 Posts: 2 Rep Power: 0	Hello friends, I am in the process of setting up an CFX simulation to model the classical example of a partially filled rotating vertical container. The fluids are water and air, with an opening on top of the vessel. I would like to share my approach and get your feedback accordingly. The goal is to model the parabolic shape of the water surface as a function of angular velocity. The parabolic shape can be calculated analytically by using the following equation: z(r) = omega^2*r^2/2g (2D) It is evident that this is a free surface flow problem. Assuming that the mesh is adequate enough, my approach is to define a fluid volume that's partially water and air, using CEL expressions as advised by section 7.18.5 of the VT manual (VOF approach). this will allow me to have consistent pressure field and volume fraction conditions. Manual: http://www.arc.vt.edu/ansys_help/cfx_mod/i1306346.html Both fluids will be continuous, and I will impose a rotating domain with omega = 500 rpm. An opening boundary condition with VOF air = 1, and VOF water = 0, and 1 atm reference pressre will be created. Omitting the rest of the steps, I would like to stop here and see if anybody has done this simulation in CFX in a similar fashion. Are there any other approaches recommended? (Such as, starting with solid domain of the container, or creating subdomains for each fluid, etc). By the way, this would be a 3D simulation. Steady state. I am getting results (CFD-POST) but they are not what I am expecting. I am not getting any errors during the solving period. Also, when I viewed the results in terms of volume fraction for each fluid, I can see an interface and the water level is at the right height. However, it looks like the rotational condition is not being set correctly. I will post some more details about my setup as soon as possible, including some pictures. Anything you can add in the meantime would be great. Thanks!

July 23, 2015, 17:34		#2
Martin_Sz Senior Member Marcin Join Date: May 2014 Location: Poland, Swiebodzin Posts: 313 Rep Power: 13	This is a big problem to make solution of domains of air and water and one of them rotating. Immersed solid is not solution for your modelling __________________ Quick Tips and Tricks, Tutorials FLuent/ CFX (CFD) https://howtooansys.blogspot.com/

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July 23, 2015, 19:38		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	What are you seeing? You will need to post some images of what you are getting, your mesh and your CCL.