Investigation on the vortex structure of propeller wake influenced by loading on the blade |
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Authors: | Bu-Geun Paik Jin Kim Young-Ha Park Ki-Sup Kim |
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Institution: | (1) Maritime and Ocean Engineering Research Institute, KORDI, Jang-dong 171, Yuseong-gu, 305-343 Daejeon, Korea |
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Abstract: | The vortex structure of the wake behind a marine propeller was investigated in terms of loading variation by using particle
image velocimetry. One hundred and fifty instantaneous velocity fields were ensemble averaged to study the spatial evolution
of the wake and the behavior of the tip vortices in the region ranging from the trailing edge to one propeller diameter downstream.
The trailing vorticity was found to be related to the radial velocity jump, and the viscous wake was affected by the boundary
layers developed on the blade surfaces. A vortex identification method using the swirling strength was employed to extract
the location of the tip vortex. The loading on the blade made a clear difference to the contraction angles. Slipstream contraction
occurred in the very near wake region, and unstable oscillation occurred because of reduced interaction between the tip vortex
and the wake sheet behind the maximum contraction point for each loading condition. The maximum tangential velocity around
the tip vortex center revealed the average radius of its core, which was used for calculating the vortex strength. Additionally,
variation of the average radius of tip vortices with the change of blade loading was related to vortex tube stretching in
the wake region. The nearly constant vortex strength continued up to one diameter downstream for light loading and design
loading conditions. |
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Keywords: | Two-frame PIV Propeller wake Tip vortex Swirling strength Vortex strength |
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