hihi I model a square fluid having four caves in and out .inlet=10 outlet 1 =3 outlet 2=4 another exit is setted to pressure=0. my question is how to set the outlet boundary specified velocity ?

Use a negative inlet, i.e. an inlet with the velocity vector point out of the domain not into it

After trying ,inlet velocity setted into control volume is not a way to use(answer is strange!) .I use the outlet fixed flow boundary (give specified flow rate)accompanied with pressure(must!) boundary . (my simulation is a model involoving multi-inlet and multi-outlet ).

uhhhh can you re-phrase that I am afraid I don't have a clue what you mean

Yeah,

brush up your english !

I don't expect perfect English we are all from different places after all, my hindi is fairly terrible! I just didn't understand the question is all