Questions about using Domain Manager

[hrbyrb]

I want to simulate the sloshing of water flow (with gravity) under excitation from the bottom. When I use the DomainManager(periodic boundary condition), I follow the instructions in the user manual, and the particles are spaced 0.5dx from the domain boundary, but in the simulation, the particles collapse towards the domain boundary, and the top surface of the water drops significantly. The figure below shows the results of 0s, 0.1s, and 0.5s.

In my application, I use create_domain(self):
domain = DomainManager(xmin=0.0, xmax=1.0, ymin=-0.5, ymax=0.5, periodic_in_x=True, periodic_in_y=True, n_layers=1.0)

Question1: What is the reason for this phenomenon? When the particle search is performed, the particles near the domain boundary do search for the particles on the other side, so does it contribute to the momentum equation?

Question2: When I used n_layers =1.0, normally this would create a layer of ghost particles in the outermost layer, but my fluid particle count increased from 4332 to 7500. I queried the information of ParticleArray and found that the tag of all particles is 0, I don't understand. Since I need to pass the properties of the original particles from the interface, I need to distinguish the ghost particles created later by DomainManager. Is there any way to do that?