the result of the velocity and pressure drop is a little strange.
 

Hi, everyone. I simulated the airlow in a box(0.25m*0.02m*0.25m) using fluent, the velocity at inlet(the bottom surface of the box) is 0.05m/s, and got the pressre drop at outlet (top surface) is 6pa/0.25m, which is close to the value i calculated by using Ergun equation. But the problem is the facet average velocity at the inlet and outlet are aslo 0.05m/s. It seems the velocity doesn't reduce from the bottom to the top. Is it resonable? And if i used a circle (r=0.005m) as the inlet, the pressure drop is very low, like 0.1pa/0.25m. So i think the pressure drop is too small. Does anybody explain it for me? I will appreciate your reply! Many thanks!