when I began to compute,the star show the message in the system window-"***error#***FIXED VELOCITY BOUNDARY CONDITION OUTFLOW EXCEEDS INFLOW BY 5 PER CENT".what can i do for it? I will appreciate of your any help!

Sometimes if your mesh is too coarse such messages are popped. Please check the mesh before proceeding for any other cause.

In fact,my mesh is very fine.when I use coarse mesh,it is ok!but when i change to more fine mesh,star pop that message! thank you help!

If you have a model with a fixed inflow and a fixed outflow (i.e. no pressure or outlet boundaries) the massflow through the system must obviously balance.

In other words, what goes in must come out.

When you have such a model, Star checks the balance to save you from making silly mistakes. If the balance is out by more than 5%, it issues this warning and stops the run. If less, it will adjust the outward velocities to compensate.

What all of this is saying is that you have made a mistake in the balance between your inflow and outflow. Check the boundary condition normal velocities and the actual boundary areas.