I use fluent to simulate the additional actuator, but i don't know how to set the changeable(or transient)boundary conditions, I hope someone can help me, thanks.

The only way, I believe, you can set a boundary condition that changes with time (or for that matter any other variable) is to use a User Defined Function or UDF. If you use this forum much you will see that most of the questions regard UDF's. They are a very useful tool, and if you plan to use fluent alot they are well worth learning. However, they are quite tricky to begin learning. The best place to start is looking at the UDF manual supplied with fluent 6 or above.

If this is the only thing you will ever want to do in fluent, it is possibale to pay someone to write UDF's for you, but I don't know anyone who dose this. This saves you the time of learning how to write them yourself.

I see. I should learn more from you. Thank you.

If you have access to the Fluent user's site (www.fluentusers.com) there's the solution to your problem if I remember well. Luca