I am doing a simple simulation based on the ErgunTest tutorial using CFDEMSolverPiso, geometry and pathches are the same with the tutorial.
The fluid is pressure drive, with the outlet and inlet boundary for p: fixedValue p1 and p0 (p1>p0), for U: both zerogradient for outlet and inlet. The wall is no slip wall.
I supposed the pressure decrease from the inlet to the outlet in the runtime, however, strange pressure is found in the bed, some cells are large than p1, some cells are small than p0. I use GAMG with GaussSeidel smoother, the convergence of p is observed.
I am struggling with the problem for almost two weeks, any suggestions what cause such abnormal behaviour??