i have read manual that when we apply mass flow or velocity at inlet and pressure at outlet then it will more robust.but when we apply pressure at inlet and velocity at outlet it will diverge the solution.The later is applicable only to compressible flow.Can anybody tell me why this is happening? the outlet mass flow is applicable to fully developed flow.so what is fully developed flow? and why it is robust for outer mass flow? Thanx

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I do not find back this information in the manuals of FINE/Turbo. Furthermore, in NUMECA software you do not have the possibility to impose static pressure at the inlet. Maybe you mean imposing the inlet total pressure? For imposing the velocity at the outlet the only way in FINE/Turbo is by imposing the mass flow.

Imposing the total pressure (and total temperature and velocity direction) at inlet and the mass flow at outlet is a valid combination for compressible flow. For incompressible flow it is rather recommended to impose static conditions (static temperature and velocity) at inlet and static pressure at outlet.

For further information on the use of boundary conditions for your specific configurations you can also contact Numeca support: support@numeca.be