Boundary condition causes MRF(steady) unconvergence
 

Hello everyone,
I tried to simulate a pump piston motion which includes both rotation and translation, for rotation, I adopted the moving mesh method, and for translation, I took UDF method. In beginning, I wanted to use MRF to give a good initial condition for the simulation, however, once I ran the simulation, warnings came out: “Divergence detected in AMG solver: pressure correction.” And I found it is the outlet boundary condition (high pressure) that leads to this unconvergence, but I don’t know how to solve this problem, can someone do me a favor? Thx!

Boundary condition:
Inlet: pressure inlet 0 pascal
Outlet: pressure outlet 35000000 pascal (35 MPa)

MRF and Initial Condition
 

A good initial condition is always useful as long as the system is continuous. However, in your case, MRF is not even applicable. You should initialize with 0 values for every field, except for Pressure and Dissipation Rate. For pressure, use a high pressure value. For Dissipation Rate, use a value of 1.0 or any positive value to ensure that is a realizable number. I am assuming you are using Ideal gas law. Therefore, temperature is another important condition, however, default value of 300 K will do equally well.