During the simulation, I find the residuals for continuity equation, momentum equation and energy equation don¡¯t drop, but go up slowly. I don¡¯t know why the phenomenon appears and what I should do. Give me some advice, please. Thank you.

Change your Under-relaxation factors in your Solver menu.

Otherwise make sure you are not trying to model an unsteady case using a steady-state solver.Also check your mesh for skew cells and high-aspect ratios.

As long as your residuals go down...thats still good.

Thanks.