Research on the feature extraction method of secondary flow in pump-jet propulsor

Secondary flow plays a pivotal role in flow separation within turbomachinery, impacting the performance of pump-jet propulsors through associated secondary flow losses. Past research has predominantly concentrated on water wing models, leading to limited insights into more intricate turbomachines. This study explores methods for extracting secondary flow characteristics in pump-jet propulsors through numerical simulations employing large eddy simulation, coupled with vortex identification techniques and analysis of velocity and pressure fields. Notable features of secondary flow include the tip leakage vortex and root shedding vortex, the latter exhibiting reverse flow and pronounced oscillations at the suction side's trailing edge. The distribution of driving forces and secondary flow intensity is evaluated using S3 flow surface theory, revealing a substantial influence of Coriolis forces at the blade root. This study proposes an innovative approach utilizing helical line techniques to form S3 approximate flow surfaces, facilitating thorough extraction of secondary flow characteristics at both blade tips and roots. This research fills existing gaps in the study of secondary flow phenomena in pump-jet propulsors, contributing valuable methodologies and a theoretical framework for evaluating secondary flow energy dynamics and related noise generation, thereby advancing the understanding of these critical elements in fluid mechanics and propulsion systems.