펌프젯 추진기 단독성능 추정을 위한 수치해석 연구

Abstract

This paper provides the results of a numerical study conducted to predict the open water performance of a pumpjet propulsor designed by Ahn et al.[10]. Changes in the thrust and torque of each part of the pumpjet propulsor according to advance ratio were analyzed by using the RANS method based on the SST k-ω turbulence model. The present numerical results were validated with the results of the open water test performed in the large cavitation tunnel at KRISO. Compared to the condition without the pre-swirl stator and duct, the thrust and torque of the rotor increased due to the effect of those two parts of the pumpjet propulsor. On the other hand, the pre-swirl stator and duct induced drag rather than thrust at advance ratios higher than 0.4. In addition, the rotational direction of the torque predicted for these two parts was opposite to that of the rotor. The forces and efficiency predicted for each part of the pumpjet showed a good agreement with those of the model test, except for the advance ratios higher than 1.0. The reason that the numerical analysis underestimates the forces and efficiency at advance ratios greater than 1.0 is presumed to be the cause of the stall phenomenon in the numerical simulation occurring earlier than in the model test. Through the local flows, the pressure drop phenomenon that can cause cavitation due to the gap flow between the rotor blade and the duct and the characteristics of the tip vortex development according to advance ratio were discussed.