[CFD_ER]

Based on overlapping grids, overInterDyMFoam was used to simulate a 2D box entrying into water at a constant speed.
The numerical model contains two sets of grids, one is a fixed background grid, and the other is a component grid that moves vertically at a constant speed.

The current problem is that when the component grid is falling, the air and water in the entire component grid are always the same as the initial moment without any change, as shown in the figure below. It seems that the air and water in the background grid and the air and water in the component grid are two independent parts.

After calculating four or five time steps, it diverges.

I hope you can help me solve this problem, thank you very much!