Nowadays, I am using CFX4.3 to model gas-solid two phase flow. It is a unsteady problem, so the residuals should oscillate. But the residuals of monitor point in my simulation become a flat line with residual steps increasing.It puzzled me very much. Does anyone know the problem? Thanks in advance.

Do you perform steady or unsteady calculations?

i perform a unsteady calculation.

Your residuals might look stationary but is your solution stationary? It also depends on where you monitoring point is located. If it is located near an inlet it might show stationary behaviour.

P. Fonteijn

(1). You may want to display the results at two iteration numbers in terms of the contour plots. (2). By comparing the contour plots at two different time steps, you can easily see the change in flow field and the specific areas or locations. (3). Area near the inlet normally converges faster because it is affected by the inlet conditions. (4). On the other hand, the exit area is always slow in convergence. Loca region with flow separation is also slow in convergence. So, the contour plots will be very useful to provide these information.