Twenty-Fourth Symposium on Naval Hydrodynamics (2003) / Chapter Skim
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Phase-Averaged PTV Measurements of Propeller Wake
Phase-Averaged PTV Measurements of Propeller Wake
Pages 916-926
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From page 916... ...
It is well known that any numerical attempts based on either potential or viscous flow model would not yield a satisfactory prediction of the formation and trajectory of tip or trailing vortices without an adequate wake sheet modeling. In the conventional numerical methods, the velocity field around a propeller blade is calculated from the position of wake sheet assumed in the previous iteration step, and a new position of wake sheet satisfying the boundary condition is determined and the process is repeated until a numerical convergence is obtained.
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From page 917... ...
The several hundreds instantaneous velocity fields were measured at four different phases of the propeller blade and they were phas~averaged to investigate the spatial evolution of the vertical structure and turbulence statistics for the propeller wake.
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From page 918... ...
Figure 3 shows the instantaneous velocity field subtracted by Uo=32.5 cm/s at the phase angle of o= 0°. The periodic wake sheets and tip vortices in the clockwise rotation are shed successively from the blade tips with a regular interval are clearly seen at J = 0.59 and 0.72.
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From page 919... ...
near-wake region due to the merging of two boundary not 06 (c) J=o.59 Figure 4: Contour of phase-averaged axial velocity layers developed on both sides of propeller blade 414 Q4 ED (a)
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From page 920... ...
Tip vortex generated from the pressure difference between upper and lower surfaces of a propeller blade is rolled up near the blade tip and forms vortex sheets. Tip vortices evolve downstream with a regular spacing periodically.
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From page 921... ...
This indicates that the turbulece intensity for axial velocity component is stronger near the tip vortices than the other wake region. The turbulence intensity of vertical velocity component also has large values near the tip vortices as shown in figure 9.
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From page 922... ...
Due to active mixing between tip vortices and wake flow, the turbulent shear stress increases at the downstream location. CONCLUSION The propeller wake in an open water condition was investigated using an adaptive hybrid PTV technique, and instantaneous velocity fields were measured at four different blade phases of 0°, 18°, 36° and 54°.
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From page 923... ...
and Lee, C.S., "Prediction of Steady and Unsteady Marine Propeller Performance by Numerical Lifting Surface Theory," Trans.
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From page 924... ...
The several hundreds instantaneous velocity fields were measured at four different phases of the propeller blade and they were phas~averaged to investigate the spatial evolution of the vertical structure and turbulence statistics for the propeller wake.
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From page 925... ...
However, we also observed the interaction between tip vortex and blade wake in the separation and the oscillation of tip vortices. The contour plots of axial velocity (figure 4)
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From page 926... ...
P., Elefante M., "Propeller wake Analysis by means of PIV", 23th Symposium on Naval Hydrodynamics, Val de Ruil (F)
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