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Prediction and Measurement of Propeller Singing: C e C Ec e Ee

This document summarizes a study on predicting and measuring the phenomenon of propeller singing. Propeller singing occurs when the frequency of vortex shedding at a propeller blade's trailing edge matches one of the blade's natural frequencies. The study used vibration and acoustic data from a bulk carrier to analyze this. Numerical models were used to calculate the natural frequencies, mode shapes, and radiation efficiency of the propeller blade. Together with a theoretical model of the interaction between vortex shedding and blade vibration, the study was able to predict which blade mode was associated with the observed singing. Comparison to measured data found good agreement between the predicted high-response, high-radiation efficiency mode and the measured singing frequency.

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Arun S
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244 views1 page

Prediction and Measurement of Propeller Singing: C e C Ec e Ee

This document summarizes a study on predicting and measuring the phenomenon of propeller singing. Propeller singing occurs when the frequency of vortex shedding at a propeller blade's trailing edge matches one of the blade's natural frequencies. The study used vibration and acoustic data from a bulk carrier to analyze this. Numerical models were used to calculate the natural frequencies, mode shapes, and radiation efficiency of the propeller blade. Together with a theoretical model of the interaction between vortex shedding and blade vibration, the study was able to predict which blade mode was associated with the observed singing. Comparison to measured data found good agreement between the predicted high-response, high-radiation efficiency mode and the measured singing frequency.

Uploaded by

Arun S
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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中國 造 船 暨 輪 機 工程學 刊 第 二 十三 卷 第 四期民國九 十三年 179

Journal 01 Taiwan Society 01 Naνal Architects and Marine Engin eers , Vol.23 , No .4, pp.179-187, 2004

PREDICTION AND MEASUREMENT OF PROPELLER SINGING

R.J. Shyu t C. Y. Hsin and w.J. Liao

Department ofSystems Engineering and Naval Architecture


National Taiwan Ocean University
Keelung, Taiwan 202 , ROC
Keywords: Propeller Singing, Vortex Shedding, Modal Analysis, Radiation Efficiency

ABSTRACT
In this paper, an analysis model is proposed to predict the propeller singing, which generally occurs when the vortex
shedding frequencies at the blade trailing edge and some na仇lTal frequencies of the blade are nearly equal. A set of
vibration and acoustic data taken during a sea trial of a bulk carrier was used to demonstrate this phenomenon. Numerical
analyses, using finite element and boundary element methods, were performed to calculate the natural fr.叫uencies， mode
shapes , and the radiation efficiency of the propeller blade. Together with a theoretical model describing the interaction of
vortex shedding and blade vibration for predicting the response of the blade due to vortex excitation, the possible mode
associating with singing can be deduced. In comparison with measured data, good agreement is shown between the
frequency ofthe predicted mode that show both high response level and high radiation efficiency and the measured singing
frequency.

propeller singing is necessary for ships with strict


INTRODUCTION
acoustic requirements at the preliminary design stage to
Noise from ship propellers may be attributed to avoid singing phenomenon.
several effects , such as propeller cavitation, turbulence , Propeller singing can take several forms , ranging
and singing. For the first two causes , the noise is broad- from a deep grunting noise to a high-pitched warbling
banded and the latter a pure tone only. Therefore , a tone noise. References [2-8] contain material relevant to this
noise can be heard once propeller singing occurs. This phenomenon. The deeper “ grunting" noise is most
tonal frequency ranges usually from 100 to 2 kH z and commonly associated with larger vessels such as bulk
has been known for a long time as the earliest reference ca訂間的 ， and in general the faster and smaller the pro-
dating back to 1911 by Von Kármán [1]. The sound is peller is , the higher the frequency will be. The noise may
sometimes very loud and the associated vibration can be be intermittent or may have an apparent period of about
s仕ong enough to cause fatigue failure on the propeller once per revolution [9]. Furthermore , singing usually
blades. The cause of this phenomenon is the frequency of occurs only within certain specific revolution ranges not
vortex shedding at the trailing edge coincides with one of throughout the whole range of propeller loading. This
the natural frequencies of the propeller blade. However, phenomenon is called “ lock-in'\In addition , the non-
the cure of this problem is normally not difficult and can linearity causes the lock-in range different between
generally be avoided by making changes to the trailing running up and coasting down the revolution speed of
edge of the propeller blade. But in some case , although engine shaft [10].
the “ anti-singing edge" was applied to the trailing edge , A bulk carrier bui 1t by Taiwan shipyard had been
the singing phenomenon still exists. Thus , prediction of observed to have a singing propeller. Accelerometers and

t Corresponding author(rjs@sena.ntou.edu.tw)

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