Affiliations: Department of Mechanical Engineering, Pohang
University of Science and Technology, San 31, Hyo-Ja Dong, Pohang, 790-784,
Korea. E-mail: sjlee@postech.ac.kr | Department of Mechanical Engineering, Pohang
University of Science and Technology, San 31, Hyo-Ja Dong, Pohang, 790-784,
Korea
Abstract: A stereoscopic PIV (Particle Image Velocimetry) technique has been
employed to measure the 3 dimensional flow structure of turbulent wake behind a
marine propeller with 5 blades. The out-of-plane velocity component was
measured using particle images captured simultaneously by two CCD cameras
installed in the angular displacement configuration. 400 instantaneous velocity
fields were acquired for each of four different blade phases of 0°, 18°, 36° and
54°. They were ensemble averaged to investigate the spatial evolution of
propeller wake in the near wake region up to one propeller diameter (D)
downstream. The phase-averaged velocity fields show clearly the viscous wake
formed by the boundary layers developed along both surfaces of the blade. Tip
vortices were generated periodically and the slipstream contraction occurs in
the near-wake region. The out-of-plane velocity component has large values at
the locations of tip and trailing vortices. With going downstream, the axial
turbulence intensity and the strength of tip vortices were decreased due to the
viscous dissipation, turbulence diffusion and blade-to-blade interaction. The
difference in the mean velocity fields measured by SPIV and 2-D PIV methods was
about 5% ∼ 10%. However, the 2-D PIV results also give sufficient information
on propeller wake beyond the region of X/D = 0.2.
Keywords: Stereoscopic PIV(SPIV), Propeller wake, Tip vortex, Wake sheet
