why dynamic mesh method give wrong results?
 

For conventional CFD study on airfoil, the air is moving, the airfoil is steady. It can give considerable results and acceptable.

In reality, the airfoil flies in air. So, I use dynamic mesh method modeling the motion.

But the results confused me. The lift is a bit smaller and the drag is 3 or 5times of conventional CFD method. why?

can anyone describe the reason?

How can I get the right result using dynamic mesh method?
Thanks!