The classical approach in one dimensional fluid power systems simulation considering the flow through hydraulic resistances is to imply a single-phase flow of an incompressible fluid. This assumption leads to significant errors in cases when the system is polluted with entrained air. In this paper the classical orifice equation describing the incompressible flow based on the Bernoulli’s equation is analysed and transferred to allow the calculation of the existence of a second disperse gaseous phase. The basic objective hereby is the examination of the different behaviour caused by a laminar, turbulent or laminar-to-turbulent transition flow field as well as its ranges.
Therefore Computational Fluid Dynamics (CFD) simulations of the single-phase flow and the two-phase flow through a hydraulic orifice are performed and the calculated discharge coefficients parameterizing the orifice equation are compared. To assure the validity of the simulations the one-phase and two-phase flow is measured using a new designed test bench. Finally the calculated, simulated and measured results are compared.