• The Journal of the Acoustical Society of Korea
• /
• v.37 no.2
• /
• pp.92-98
• /
• 2018

This paper is a study on the generation mechanism of propeller singing based on the cavitation tunnel test, underwater impact test, finite element analysis and computational flow analysis for the model propeller. A wire screen mesh, a propeller and a rudder were installed to simulate ship stern flow, and occurrence and disappearance of propeller singing phenomenon were measured by hydrophone and accelerometer. The natural frequencies of propeller blades were predicted through finite element analysis and verified by contact and non-contact impact tests. The flow velocity and effective angle of attack for each section of the propeller blades were calculated using RANS (Reynolds Averaged Navier-Stokes) equation-based computational fluid analysis. Using the high resolution analysis based on detached eddy simulation, the vortex shedding frequency calculation was performed. The numerical predicted vortex shedding frequency was confirmed to be consistent with the singing frequency and blade natural frequency measured by the model test.

• Journal of KSNVE
• /
• v.23 no.2
• /
• pp.16-19
• /
• 2013

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2011.04a
• /
• pp.471-472
• /
• 2011

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2009.04a
• /
• pp.476-476
• /
• 2009

Periodic vortex separations generate periodic vertical forces acting on a trailing edge of an airfoil. When a natural frequency of the trailing edge of the airfoil is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appear, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, a theoretical model is proposed and applied for modeling an airfoil singing. Results are compared with experimental measurements which are carried out in an anechoic wind tunnel.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.2
• /
• pp.115-121
• /
• 2010

Periodic vortex separations generate periodic vertical forces acting on a trailing edge of an airfoil. When a natural frequency of the trailing edge of the airfoil is close to a vortex shedding frequency, an amplitude of the edge oscillation becomes maximal; it makes intensive noise called singing. Motion of the trailing edge may also feedback to the vortex shedding so that self-sustained oscillation appears, and a resonant frequency is locked in some interval of the speed of the incident flow. In this study, a theoretical model is proposed and applied for modeling an airfoil singing. Results are compared with experimental measurements which are carried out in an anechoic wind tunnel.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.36 no.2
• /
• pp.117-125
• /
• 2000

The waveform and spectrum analysis of Tursiops truncatus(bottlenose dolphin) sonar signals were carried out on the basis of data collected during the dolphin show at the aquarium of Cheju Pacificland from October 1998 to February 1999. When greeting to audience, the pulse width, peak frequency and spectrum level from the five dolphins'sonar signals were 3.0ms, 4.54kHz and 125.6dB, respectively. At the time of warm-up just before the show, their figures were 5.0㎳, 5.24kHz and 127.0dB, respectively. During the performance of dolphins, with singing, peak frequency ranged 3.28∼5.78kHz and spectrum level ranged 137.0∼142.0dB. With playing ring, pulse width, peak frequency and spectrum level were 7.0㎳, 2.54kHz and 135.9dB, and when playing the ball, the values were 9.0㎳, 2.78kHz and 135.2dB, respectively. The values determined from the five dolphins during jump-up out of water were : pulse width 2.0㎳, peak frequency 4.50kHz and spectrum level 126.8dB. When they responded to trainer's instructions, the values were 2.25㎳, 248kHz and 148.7dB, respectively, and greeting to audience, the peak frequency and spectrum level were 5.84kHz and 122.5dB. During swimming under water, peak frequency and spectrum level were determined to be 10.10kHz and 126.8dB. It was found that there exited close consistencies in pulse width, frequency distribution and spectrum level between whistle sounds and dolphin's sonar signals. Accordingly, the dolphins can be easily trained by using whistle sound based on the results obtained from the waveform and spectrum of the dolphin's sonar signals.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.797-803
• /
• 2000

Recently, the singing phenomenon was encountered during the sea trials of high speed catamaran and 46,000 TDW product carrier and remedied after various treatments, which were based on the reduction of vortex shedding strength and the avoidance of resonance, respectively. And, the numerical approach for structure-acoustical problem like singing phenomenon was established using MSC/NASTRAN and SYSNOISE. In this paper, the effectiveness of numerical approach was verified through the control of singing noise. And the results according to the modification were also discussed. Finally, the future works were described to enhance the numerical approach pattern for singing phenomenon.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.10a
• /
• pp.753-756
• /
• 2013

The demand for sailing yacht is increasing in consonance the improvement of people's live. These yachts can be dually propelled by wind and by diesel engine power. A singing (humming, whistling) phenomenon induced on the propeller was discovered on a 55-foot catamaran sailing yacht. As a result, an increase in the structural vibration of the stern tube room and propulsion system with abnormal noise was detected due to this flow. In this study, the cause of the phenomenon is investigated and its possible countermeasures proposed.

• Journal of the Society of Naval Architects of Korea
• /
• v.31 no.3
• /
• pp.59-64
• /
• 1994

A study was conducted to investigate the propeller singing place of an 86, 000 ton Deadweight Crude Oil Tanker. In preliminary study, proper use of finite element analysis was verified by comparing with the result of hammering test in the air. Then the finite element analysis was carried out for the blade in the water and compared with the noise measurement during sea trial, which enabled to confirm the local resonances of blade structure. Result of the study showed that the singing occurred most probably at trailing edges on the blade tip over 95% of propeller diameter. Owing to edge cutting of a successfoul remdial action, the singing excitation forces seemed to be reduced whereas the vibration characteristics of the blade was not changed.