Proceedings of The Fifteenth (2005) International Offshore and Polar Engineering Conference
Seoul, Korea, June 19−24, 2005
Copyright © 2005 by The International Society of Offshore and Polar Engineers
ISBN 1-880653-64-8 (Set); ISSN 1098-6189 (Set)
Identification of Propeller Singing Phenomenon
through Vibration Analysis of Propeller Blade
Hyung-Sik. Park, Su-Hyun. Choi, Nho-Seong. Kim
Vibration & Noise R&D Team, Daewoo Shipbuilding & Marine Engineering Co., LTD.
Geoje-si, Gyeongsangnam-do, Korea
KEY WORDS: Propeller singing; natural frequency; vortex shedding
frequency; F. E.(finite element); vibration analysis; unit force; radiation
efficiency.
whether anti-singing edge treatment is applied or not, the vortex
shedding frequencies are not changed. The parameters determining the
vortex shedding frequencies are the thickness of the trailing edge and
the local average flow velocity around trailing edge. After anti-singing
edge treatment, the amplitude of excitation due to the vortex shedding
is reduced.
To prevent the propeller singing, it has to be designed so that the
natural frequency of a propeller blade doesn’t match the vortex
shedding frequency at the trailing edge of blade. However, anti-singing
propeller design is actually difficult, because the vibration mode shapes
of the propeller blade are very complicated.
In this paper, F.E. analysis has been conducted for the propeller blade
in order to estimate the resonance frequency at which singing
phenomena are likely to occur. Through free and forced vibration
analysis, the natural frequencies of dominant vibration mode have been
determined. Radiation efficiency has also been calculated each
vibration resonance frequency. Among those frequencies, the propeller
singing frequency has been determined in cooperation with the
calculation results of the radiation efficiency.
INTRODUCTION
FINITE ELEMENT MODEL OF PROPELLER
Propeller singing phenomenon is defined as the resonance between the
local natural frequency of the propeller blade tip and the vortex
shedding frequency at trailing edge of the blade. Propeller singing
phenomenon makes very intensive levels of radiated noise. The
possible causes of this propeller singing are the vortex shedding at the
trailing edge of propeller blade, self-excited vibration by blade
fluttering, the friction at the stern-tube bearing, etc. But, in general the
singing phenomenon occurs when the frequency of the response related
to the vibratory amplitude of the blade coincides with vortex shedding
frequencies of trailing edge of some blade sections. The vortices in the
immediate vicinity of that part of the blade will also shed
approximately at this frequency. This will lead to increase in coherence
length of the blade trailing edge vibration and more force will be
applied to the trailing edge and then amplitude of vibration will also
increase. If this process continues to develop until a large part of the
blade takes part in vibration, then a strong vibration will take place and
will lead to the propeller singing phenomenon.
The latest paper shows the peculiarity of vortex shedding as follows:
Subject Vessel and Propeller
ABSTRACT
Propeller singing phenomenon occurs very often in ships. It is in
general caused by the resonance between the local natural frequency of
the propeller blade tip and the vortex shedding frequency at trailing
edge of the blade. In this paper, the vibration mode characteristics of
propeller blades in a ship are investigated by vibration analysis using a
commercial F. E. program. According to the analysis results, propeller
singing frequencies can be estimated from free vibration analysis and
forced vibration analysis using a unit force. These results are verified
by a method using the radiation efficiency of the propeller blade to be
obtained from another commercial program. According to the study,
the calculated singing frequencies of the propeller are in good
agreement with the measured ones carried out during sea trials or at an
actual sailing condition of the ship
The deadweight of the subject vessel for this study shall be 104,420
metric tonnes. The main characteristics of the subject vessel and the
propeller are shown in Table 1.
Table 1. Main characteristics of the subject ship and the propeller
L.O.A
L.B.P
Breadth (Moulded)
Depth (Moulded)
Scantl. Draft (Moulded)
591
Propeller Diameter
248.0 m
238.0 m
43.0 m
21.0 m
14.3 m
8.0m
Number of Propeller Blade
4EA