In the numerics pane, the default value of fluid pressure correction scale (PPG_DEM) is 10. I notice the prompt that the number is used to “scale initial fluid pressure correction equation residual when NORM_G=0”. The fluid nornalization (NORM_G) is used to "normalize the gas continuity equation residual " to speed up calculations. How to understand PPG_DEM and NORM_G more clear? In what cases, their suggested values need to be changed and how to change them?
when you use NORM_g=0 the initial residual for pressure correction is divided by PPG_DEM (default value is 10) which has the effect to tighten the convergence criteria. If you set a value of PPG_DEM=1 then the initial residual is not scaled down, and it will typically accelerate convergence.
Convergence criteria typically need to be adjusted on a case-by-case basis to find a compromise between speed and accuracy. You can start with default values and experiment to see the effect on solution.