STUDY ON INSTABILITY MECHANISM AND EVOLUTION MODEL OF PROPELLER TIP VORTICES

Abstract

The propeller wake dynamics is a fundamental but very complicated fluid mechanics problem. Its complexity comes from its sophisticated vortex system, which keeps evolving in high-speed shear layer flow. The mechanism of propeller wake behaviors such as the evolution from stable regime to unstable regime and the flow phenomenon in a complex operating environment have always been difficult and hot topics in the field of fluid mechanics. From the perspective of engineering applications, propeller wakes are directly related to the macroscopic characteristics of marine structures, a better understanding of the dynamic characteristic of the propeller wake under multiple operating conditions helps to improve the propulsion performance related to vibration, noise, and structure problems and has important practical significance for the design and optimization of next-generation propellers with good comprehensive performance. In this paper, the propeller wake dynamics are analyzed numerically using DDES, LES and NTM methods and experimentally based on PIV flow measurements, and the triggering mechanism of the instability of the propeller wake is revealed. Based on the evolution mechanism of the tip vortex in the uniform inflow, an evolution model of the tip vortices is proposed. The proposed model can accurately reproduce the evolution process of propeller tip vortex, predict the instant and position of tip vortex merging, which is of great significance to the prediction and control of propeller flow noise and the design of propellers with excellent performance.