My geometry is large in size which makes meshing coarse while fulfilling the upper limit of 512k elements.
Would you mind explaining further on how to get a better result by looking into cell courant number and flow residence time, thanks so much Rob and Karthik!
I found that when COUPLED is chosen as the solution method, under 'Control', the flow courant number is 200 now, which I know the desired value should be less then 1. What should I do to reduce the flow courant number (or just directly change it to my desired value) and what to do with the flow residence time on Fluent?