Experimental Study on Evolution of Cavitation Flow Structure in Hump Region of Waterjet Pump

The waterjet propulsor is a new type of marine propulsion system, which offers the advantages of high speed, good maneuverability, and low vibration and noise. As the core component of the waterjet propulsor, the primary role of the waterjet pump is to provide sufficient thrust for the vessel. However, the waterjet pump is prone to be troubled by the hump phenomenon. As the pump operates in the hump region, it may encounter issues such as flow interference and exacerbated vibration and noise, which are closely related to cavitation phenomenon in the pump. To analyze the evolution of cavitation flow structure in the waterjet pump when operating in the hump region, this study utilized high-speed photography to obtain the cavitation flow structure at different cavitation development stages under the hump peak condition. The cavitation stages involved include the cavitation inception stage, cavitation development transition stage, first critical cavitation stage, critical cavitation stage, and breakdown cavitation stage. During different cavitation development stages under the hump peak condition, the blade tip region exhibits distinct cloud cavitation induced by the tip leakage vortex (TLV). As the NPSH decreases, the frequency of cloud cavitation shedding increases, the scale of the cavitation cloud at the leading edge of the blade decreases, and the scale of the cavitation cloud accumulated at the rear of the flow passage increases. This study on the cavitation flow of the waterjet pump is significant as it contributes to enhancing the anti-cavitation performance and reducing vibration and noise. It provides scientific guidance and engineering practice for improving the safety and stability of waterjet pumps during operation.