The Identification of Tip Leakage Vortex of an Axial Flow Waterjet Pump by Using Omega Method and Liutex

The tip leakage vortex (TLV) is a common phenomenon in the field of rotating machinery. The formation and evolution of TLV can lead to some adverse effects, such as the interfering with the main flow, the occurrence of vortex cavitation, etc. This paper investigates the structure of TLV in an axial flow waterjet pump by using two vortex identification methods, namely the omega method and the Liutex. These two criterions can capture the primary characteristics of the vortex structures with different vorticity strength in the flow passage and the tip gap region. As the cavitation number decrease, the tip leakage cavitation and the sheet cavitation on the suction surface of the rotor blade present evident interactions with the TLV. The accuracy and capability of these two methods present different effects. The Liutex method can not only capture more detailed vortex characteristics in the unstable regions but also some weak vortex structures alongside with the TLV core.