i have a particles size range from 2oo nm to 3000nm from 600 to 3000 it is ok but when i decrease the range towards smaller diameters it says that divergence detected in AMG solver also i want to ask that how to calculateĀ  the turbulent kinetic energy and specific dissipate rate. a member of the ansys replied that i have to calculate both turbulent term by formula but in formula there is a velocity gradient i only have one velocity initially how can i dteremine the velocity gradient before starting the calculation.

thank you for the support