Fluids

Separating Bodies

• Super_Panda
Subscriber

Hello guys,

So I have been tasked with modeling the flow patterns of two plates being rapidly separated, but of course when my UDF separates the bodies there is zero volume cells between them because, well, there is no mesh there once they separate. I have played around with overlapping mesh, #ANSYS18Fluent, but the overset tool doesn't seem work with solid bodies.

Is this even possible? I am using ANSYS 18 and fluent as my solver.

• Vishal Ganore
Ansys Employee

Here is the simple 2D case solved without using motion UDF. Motion is applied directly to the wall and results are calculated.  Are you trying to do something similar?

• Super_Panda
Subscriber

No. I have two separate bodies (plates) in contact with one another. My UDF then rapidly accelerates one of the plates away, breaking the contact. This break causes the module to fail due to zero volume cells as there is no mesh between the bodies now.

The basic geometry is below. Where the right hand side is all wall type. My UDF then accelerates my solid away from the wall, but as you can see this is not possible as there is no mesh "between" the wall and the solid because in workbench they are one and the same.

• Vishal Ganore
Ansys Employee

I am confused with your problem statement and not sure what you are trying to do. I could see four surface bodies in your geometry. Where is the solid? Which body in your geometry is moving and in which direction??

• Super_Panda
Subscriber

The hole is the solid and moving left. The other four regions are the fluid and their corresponding interface regions.

• Super_Panda
Subscriber

• Vishal Ganore
Ansys Employee

You could have one layer of cells near right wall separating solid from the wall at time t=0.

Something like this:

Would you be able to share your project file achieve

• Super_Panda
Subscriber

I need to simulate the case of a plate being separated from another body, so i.e. a scenario where flow has to move into the space created when the two bodies separate. Effectively there must be no fluid and then when the bodies separate the fluid must then flow into the gap created, hopefully creating a weak shock, due to the high pressure gradient. Going to try your idea but initialise the area in front of the plate as a vacuum. I will share my archive once i have my mesh finalized.

• Vishal Ganore
Ansys Employee

Ok. So you have two overlapping walls (fluid domain wall and solid body wall). I will try to investigate how to handle such condition in Fluent but I am guessing that you need to have at-least one layer of mesh separating both the walls.