Learning Forum

[WEI LI]

Hi there,

The ball is driven by fluid. Additionally, the ball will hit and interact with the wall, such as bouncing back or just sticking on the wall.

A daily example is shaking a cup of water with an ice cube. I want to model the ice's movement and the water's flow field inside the cup.

My opinion is Ansys Fluent should not be sufficient. Maybe Fluent coupled with transient structural or with Rocky?

Please share your thoughts with me. 

Thank you and regards.

 

[NickFL]

Is this like a ball check valve? There used to be a tutorial (very simple 2D, but the thought process was excellent). If you are not expected to have any deformation in the solid body or are not interested in the stresses of the object, then you can leave the Mechanical part out and simply conduct the simulation in CFX or Fluent. There is also the 6DOF solver in Fluent that you may want to consider. Going to Rocky may be good if you had a large number of objects, but it seems like you only have one.

[WEI LI]

Hello Nick, thank you for your reply. I would not say it is like a ball check valve. What I want to simulate is literally applying an oscillating rotational speed to a cylindrical chamber full of water with a bead in it.

I am not interested in deformation and stress. However, CFX or Fluent may not be sufficient because I do not think it would consider the interaction between the bead and the wall. I have tried 6 DOF, but when to bead approaches the wall, an error that says, "negative volume mesh detected", pops up.

I agree Rocky seems to solve a large number of spherical objects...

[Rob]

Rocky is really for lots of smaller particles so not one large one. 

6DOF can be used, but you need to add the wall contact checks: you're not permitted to actually make contact because it breaks the topology. Any shape is permitted but you'll need to extend the UDF to avoid and mimic the body contact. 

Another option is the macro particle model. That's sphere's only but otherwise potentially the simplest option. 

[WEI LI]

Thank you for your info. Will definitely dig deeper into the macro partical model. However, Rocky seems promising as Marcelo brought up in the below reply. Not sure....

[Marcelo Precoppe]

There are certainly many ways to tackle this. CFD-DEM co-simulation using 2-way coupling (Rocky and Fluent) could be an effective one. However, given the oscillating rotation of the geometry and its interaction with the water, I believe the easiest, fastest and possibly most accurate way would be to use Rocky's SPH feature:

[WEI LI]

That animation looks awesome. I have not used Rocky before. It seems like it is able to model a single sphere.

Is there any tutorial or information regarding the animation? Thank you so much in advance.

 

[Marcelo Precoppe]

Surely, Rocky can simulate all kinds of shapes, sizes and numbers of particles (but large numbers of particles and very small particles result in long simulation times). Rocky can also simulate fluids using smoothed-particle hydrodynamics (SPH) and its interaction with particles and walls. ESSS, the company that developed Rocky have several tutorials on their support page (https://support.esss.co/). Hopefully, an Ansys employee can guide you here on the forum on how to access them.

[Rob]

The Rocky tutorials moved onto the Ansys Learning Hub (subscription is required) and content is there/coming for the Learning section on here (free), and there are fairly comprehensive guides in the Rocky Help system.