The gap size doesn't appear too small. Perhaps it is my remeshing parameters that are wrong?
Under the "Dynamic Mesh" tab, I have enabled Smoothing (default parameters) and Remeshing. Under the remeshing tab, I have checked "Local Cell," "Local Face," and "Region Face." Furthermore, I changed the "Parameters" in Remeshing to "Use Defaults."
I then created dynamic mesh zones for each inlet/outlet and the fluid zone. I did not create a dynamic mesh zone for the "interior" object. Each zone is set to "Deforming" and the parameters are copied from the "Zone Scale Info" box.
Finally, the "wall" object is set to a user-defined function and "deform adjacent boundaries" is checked.
What is confusing to me is that for min. scale length, the reported and entered values are no less than 0.26. My greatest displacement per timestep is 0.15 mm. However, when I get the "negative cell volume" error and check the min length, it is 0.14mm. It appears as though remeshing is not doing its job (though I suspect this is because I have an incorrect setup).
Please let me know if you can think of any solutions! I appreciate it!