Numerical Simulation of High-pressure Cavitation Characteristics of Thick Orifice Plate

• Transient simulation can reflect transient and variable cavitation flow • There is a periodic cavitation phenomenon between cavitation and non-cavitation flow • In a certain pressure drop range, periodic cavitation will occur in orifice flow • Periodic cavitation will produce high-frequency and high-pressure fluctuations Hydraulic cavitation is a complex phenomenon involving the formation, growth, and collapse of bubbles within liquids. It is commonly encountered in pipeline transportation systems, where it poses significant risks to system integrity and operational safety. The traditional approach to predicting cavitation onset relies on the dimensionless cavitation number; however, this method has notable limitations when applied to variable-diameter throttling structures, such as orifice plates, under practical working conditions. To investigate the cavitation flow characteristics of the variable-diameter throttling structure, this study utilizes computational fluid dynamics (CFD) simulations to examine the cavitation flow characteristics in thick orifice plates subjected to an upstream pressure of 3.45E7 Pa. Through steady-state simulations, the critical pressure ratio for cavitation inception at the orifice plate was determined to be 0.45. Yet, transient simulation results show that using critical pressure ratios to define the onset of cavitation is inaccurate because there is a transition state between the stable and unsteady cavitation states. This transitional state, termed the periodic cavitation state, occurs within a downstream-to-upstream pressure ratio range of approximately 0.37 to 0.44. In this range, cavitation bubbles experience periodic growth, detachment, and collapse, generating significant pressure fluctuations. In addition, at a fixed pressure ratio of 0.41 and upstream average pressures of 1.38E7 Pa, 4.14E6 Pa, 2.07E6 Pa, and 6.89E5 Pa, the change pattern of the orifice plate pressure is generally similar to that at an upstream average pressure of 3.45E7 Pa. The upstream points have more significant cavitation cycles and the square of the cavitation frequency is proportional to the upstream average pressure. The results of the study can provide guidance for the prediction and prevention of cavitation in liquid pipelines, and for the safe design and risk assessment of liquid pipelines.