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Gaseous cavitation is an important issue that introduces negative effects on the performance of hydraulic systems. The lumped parameter modelling approach is widely adopted in the research of hydraulic applications due to its quickness and convenience to apply at the system level. For this reason, a novel lumped parameter model of cavitating orifice flow based on a control volume concept is presented in this paper. In particular, a procedure of calibrating the unknown model coefficients is provided by using the computational fluid dynamic (CFD) method as well as test data. A test rig for studying cavitation in an external gear pump is set up with a variable orifice at the inlet port. The four coefficients in the CFD cavitation model is first identified by the measured mass flow rate through the test orifice; then the CFD simulated fluid field offers required information including the average air mass fraction in downstream region to determine the two coefficients of lumped parameter (LP) model. To further verify the calibrated models, another test at a different pump speed is carried out to compare it to the model prediction. Good matching with experiments justifies the proposed approach and the calibration procedure. Suggestions for future work include extending the approach to the study of hydraulic valves and high-speed pumps. [ABSTRACT FROM AUTHOR]