Defining Outlet conditions

Luis

For a cylindrical chamber, I need to set up an outlet boundary condition, where the tangential and radial velocities are zero, but where the axial velocity has to satisfy the conservation of mass imposed in the inlet (i.e. Uz is unknown ). My question is: what kind of arrangements? or what type of B.C I need to impose in order to satisfy the conditions explained above.

A good idea will be the use of the average static pressure. However,this will not satisfy the condition of horizontal velocities equal to zero. Another way could be the use of the cylindrical coordinates option. Thus, I will be able to set up those two velocities to zero, but this carry on the problem of the definition of the axial velocity, which is unknown.

Thank you