Simulation of fluid moving through an opening valve - issues with overset mesh interface

Hey guys,

I'm trying to simulate compressed air flow through a pipe as a valve is opening in a transient simulation.

I am trying to simulate this by using an overset mesh. The background mesh is represented as the valve that the fluid moves through, and the overset mesh represents the fluid around the poppet(the section of the valve that moves upwards to let the fluid through). I would like to hole cut the mesh to remove the solid section that represents the solid body of the poppet. The background mesh representing the fluid in the valve already has the volume represented by the solid poppet at the "open position" cut out of the volume. I'd like to be able to move the overset mesh via dynamic mesh events upwards over the length of the simulation to simulate the opening of the poppet and see the fluid movement.

This is the setup of the mesh so far:


My problem is that after I create the overset interface and I try enable the hole cutting, I always get the error that zone 4 (the background mesh) has only dead cells due to failing dead cell flood filling, and that the mesh may not be sufficiently closed, or not sufficiently overlapping boundary zones.


Whenever I examine the sead cells that lead to the flood filling (using the commands define/overset-interfaces/options/debug-hole-cut and define/overset-interface/display-cells), they demonstrate that the sead cells originate from the region that I want to be made void and solid, so they are originating in the right place, I think. The other reason that was given online for failing dead cell flood filling was mismatching cell resolution between the background and component  mesh; however, the resolution is pretty similar:

This is the background mesh

and this is the component mesh.

This is my first time using overset meshes and I have gone over the sections in the help and tutorial guide a couple times, but I'm a bit concerned about the setup. I currently have a cutout in the background mesh to represent the volume of the poppet at its "open position", is the intersection of this void section with the hole cutout i'm trying to create with my component mesh the cause of the flood failing?

I've thought about removing this cutout from the background mesh, and having the entire poppet be represented by a hole cutout created by the component mesh and background mesh. One of the difficulties of this approach would be that, the top wall of the cutout of the poppet would intersect with the top wall of the background mesh at the end of the valve motion, which can't happen in overset meshes. 

If anyone has dealt with overset meshes in this kind of situation before, or has looked at fluid through an opening valve, any input or advice would be really appreciated. 


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