I want to simulate mold filling of a bar mold with a semisolid alloy by means of FLOW3D cfd package. but there are some problem. for example when I input a file I encounter an error like "level   1 error in subroutine rdstl: level   1 error in subroutine rdstl"in preprocessor. what can I do? does my .stl file have any faults?other problem with another project is that when i want to solve the problem I encounter an error like "convective flux exceeded stability limit".repeatedly. is my meshing insufficient? how can I solve that too?any useful guide is appreciated.thanks a lot.