I am doing blower simulation with sliding mesh. The output residual seems not right ( -1 order of magnitude). The mesh is pretty coarse, about 100 circumferentially. After 6 cycles of spin, the residuals are still fluctuating about. Is that normal? Can someone give me a clue. Thanks in advance.

For transient simulation, the output is NOT residual: it's rate of change in time. So probably your solution is OK.

If it is 'rate of change'. You can still check residual levels by changing 'rate' switch in Analysis Control->Output Control->Monitor Numeric Behavoir to 'residual'. Then see whether is really wrong or not.

Thank you all for advice. Very helpful.