I have simulated TFM simulation and it runs fine but when I add UDF for granular viscosity, I get divergence error due to back flow after certain time steps? What are the possible reasons for this and How to modify UDF to avoid divergence (floating point error)?
Minimum Orthogonal Quality = 7.12847e-01
Maximum Ortho Skew = 2.87153e-01
Maximum Aspect Ratio = 3.49884e+00