The main objective of present study is to investigate the flow characteristics of complex flow around a marine propeller using a two-frame PIV (Particle Image Velocimetry) and SPIV (stereoscopics PIV) techniques. The rotating propeller of 4 blades was tested in a cavitaion tunnel without any wake screen. Hundreds of instantaneous velocity fields were measured at nine phases of the propeller blade and phase-averaged to investigate the spatial evolution of the flow around the propeller. The nearly constant circulation continues up to one diameter downstream region at light and design loading conditions. Strong out-of-plane motion appears at wake sheets as and viscous wake in Z-direction took place. To find out the effectiveness of it in the cavitation tunnel, the results of SPIV measurements have been compared with those of 2-D PIV measurements in this study.
Larger and faster marine vehicles have been designed to have heavy loading on propeller blades. However, the increase of propeller loading may cause some problems such as noise, hull vibration, and cavitation at high speed. The geometry of a propeller should be optimized to solve these problems. Generally a modern propeller blade has a complicated geometry, making the wake behind a propeller more complicated. Therefore, the reliable wake analysis based on detailed experimental measurements can give useful information to optimize the geometrical shape of a propeller.
The marine propeller performance has been studied by many researchers using the potential-based panel method. However, the numerical analysis needs adequate wake sheet modeling based on the experimental data or special theory to yield a satisfactory prediction for the formation of tip or trailing vortices. In addition, it is very important to predict the strength and trajectory of the tip vortices inducing energy loss in propulsion, hull vibration and noise.