Learning Forum

[ivan.beltracchi]

Hi everyone, I'm a Ph.D student and I'm studying the effect of steel fibers orientation inside the HPFRC. I'm trying to simulate with a CFD approach the casting of fresh concrete. Inside the material (modelled as a non Newtonian fluid) I need to put randomly the fibers. For this condition I've thought about DEM modelling. I would like to better understand the modelling condition:

-how can I model the flowing of the material (concrete+fibers) from an initial volume, which is located at a certain height, to the formwork below it (with air inside it initially)? There is a condition of falling for a certain distance (no contact between initial volume and formwork) and an impact of the material in a central surface at the top of the formwork .

-for the DEM of the particles, can I use Ansys Rocky (but I suppose that I need a license) or do I need to use a coding file to implement? 

Thank to everyone who will help me.

Ivan

[victor.garbe]

Ivan, Tutorial 14 gives you a general overview of a simple CFD-DEM 2-Way coupled simulation Chapter 14: Tutorial - Fluidized Bed (ansys.com)

For this application, I suppose you'll need Multiphase flow. So Chapter 14: Tutorial - Fluidized Bed (ansys.com) shows you how to setup such a case.

To model the interaction forces (specifically drag) between non-newtonian fluids and particles, you may also need a special correlation: Chapter 7: Dhole, Chhabra & Eswaran Drag Law Module (ansys.com)

[ivan.beltracchi]

ok thank you so much fo the documentation.

I have another question regarded to the generator of fluid, because there is a condition that i can't understand.
For my problem is it necessary to model two solid volumes (one where there is initially air and the other where there is the concrete with the fibers) or it could be better to use inlet-outlet surface to generate the flowing material inside directly of the target volume? 
For my problem there is only the condition of filling a closed volume. in this second approach, how can i manage it? 

Another doubt is that, at the top of the cast, there is a plane surface along which part of the flowing volume of the material can impact (i have a hollow rectangular volume in the central zone, so the material can fill the volume laterally of this surface)

[victor.garbe]

You'll need to patch the regions in Fluent with the respective fluid phases for air and concrete. You don't need seperate zones, just to mark up the regions with cell registers where each phase will be occupied

[Rob]

I suspect the mixing tank tutorial (16) will be of use too. The concrete and air would be phases in Fluent, and that's covered as part of the two way coupling. 

[ivan.beltracchi]

Ok, so don't i need to create an inlet or an outlet surfaces for my problem? it's just an interaction of volumes with different fluids.

 
For the boundary condition mentioned before (a central surface of impact) how can i manage it? 

[Rob]

Pretty much. You may find a pressure boundary on the open top to be useful to help Fluent's stability. 

Surface of impact?