Omkar's reply is how we would do this.
Given that the gears overlap space we cannot use a rotating region, however you can do Motion and Free Surface to see how the fluid moves due to the gears.
Feel free to try this on a 2D slice of a model to get your bearings on how this would work
Thanks for your reply.
If you have any suggestion for the motion setup for gear-driven flow?
How should I setup the rotation speed because it cannot using rotation region?
Is it reasonable that set the rotation speed to driving wheel and driven wheel at Motion?
Thanks very much.
You would use the motion setup task instead of a rotating region. You would use the perscribed angular motion definition for both gears.
More often I would actually end up using the combined linear and angular motion so I can place my gear outside of my flow domain when building my CAD. Then use the linear initial position setting to place my gear in space where I need it. This way you don't have a imprint or ghost in the mesh where the gear was initially in CAD. This allows the flow domain mesh to be much cleaner and more efficient.