Non-Uniform girds in SIMPLE

Mike

Hi,

I have written a code for NS equations for a duct flow with variable density and viscosity based on SIMPLE method. I tried to improve the acuracy by usung nonuniform grids, however I noticed that the convergence criteria is different. In the uniform grid the term b in pressure equation become very close to zero (say order of 10^-12 to 10^-16), while in the nonuniform grid it does not change, no matter how many iterations I use and the order is about 10^-4. To my surpirse the results are very similar. Am I doing something wrong or is it normal to observe such a thing? Has anyone used non-uniform grids in a cyclindrical system so I can verify my code?