Analysis of unstable vortical structure in a propeller wake affected by a simulated hull wake |
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Authors: | Bu-Geun Paik Kyung-Youl Kim Jung-Yeop Lee Sang-Joon Lee |
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Institution: | (1) Maritime & Ocean Engineering Research Institute, KORDI, Jang-dong 171, Yuseong-gu, 305-343 Daejeon, Korea;(2) Department of Mechanical Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang, 790-784, Korea |
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Abstract: | A two-frame PIV (particle image velocimetry) technique was used to investigate the flow characteristics of a complicated propeller
wake influenced by a hull wake. As the propeller is significantly affected by the hull wake of a marine vessel, measurements
of the propeller wake under the hull wake are certainly needed for more reliable validation of numerical predictions. Velocity
field measurements were conducted in a cavitation tunnel with a simulated hull wake. Generally, the hull wake generated by
the hull of a marine ship may cause different loading distributions on the propeller blade in both the upper and the lower
propeller planes. The unstable propeller wake caused by the ship’s hull was interpreted in terms of turbulent kinetic energy
(T
KE) to obtain useful information for flow modeling. The unstable or unsteady phenomenon in the upper propeller wake was identified
by using the proper orthogonal decomposition (POD) method to characterize the coherent flow structure with turbulent kinetic
energy. Strong unsteadiness appeared in the second and higher modes, largely affecting the downstream flow characteristics.
The first eigenmode can be used to appropriately identify the tip vortex positions even in the unstable downstream region,
which are helpful for establishing reliable wake modeling. |
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Keywords: | |
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