In my understanding PISO is much better than SIMPLEC but it seems PISO gives troubles for my case. I tried switching to SIMPLEC (first the residuals were increasing with every iteration right after starting simulation but then on using Higher-Order Relaxation the residuals decreased) but the residuals keep on diverging. I am trying to control it by reducing the under-relaxation factors as per Fluent Manual Recommendation (For SIMPLEC the manual recommends the Pressure need not necessarily be changed. Is there anything else I could do?nThank you.nThe results are much more ordered but then the Cd value is still low.n