컨테이너 운반선의 회전하는 프로펠러 주위 유동에 대한 PIV 계측 및 해석

Abstract

The flow characteristics around a propeller rotating behind a container ship model were investigated using a two-frame PIV (Particle Image Velocimetry) technique. Ensemble-averaged mean velocity fields were measured at four different blade phases to investigate the flow structure of the propeller inflow and the near-wake. The propeller inflow in the upper plane above the propeller axis is quite different from that below the propeller axis. In the upper region above the propeller axis, most of the inflow comes from the hull wake and the axial velocity is very small. As the inflow moves toward the propeller plane, its axial velocity component increases rapidly. The axial velocity distribution of the propeller inflow is asymmetric with respect to the vertical center axis. The boundary layer developed along the hull bottom surface of the ship stern forms a strong turbulent shear layer, affecting the vortex structure in the propeller near-wake. The mean velocity fields show velocity deficit in the regions near the blade tips. As the flow develops in the downstream, the trailing vortices formed behind the propeller hub move upward slightly due to the presence of the hull wake and free surface. The turbulence intensity has large values in the regions around the tip and trailing vortices. As the wake moves downstream, the strength of the vorticity diminishes and the turbulence intensity increases due to turbulent diffusion and active mixing between the tip vortices and adjacent wake flow.