• The Journal of the Acoustical Society of Korea
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• v.43 no.1
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• pp.112-121
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• 2024

The pipping system is widely used in many industries as equipment for transporting fluids over long distances. In high-pressure pipe, as the speed of the fluid increases, a loud noise is generated. Therefore, various studies have been conducted to reduce pipe noise. In this paper, a pipe noise analysis was developed to predict and quantitatively assess the flow-induced vibration and acoustic-induced vibration due to valve flow in high-temperature and high-pressure. To do this, a high-fidelity fluid analysis technique was developed for predicting internal flow in the pipe with valve. In additional, the contribution of compressible/incompressible pressure by frequency band was evaluated using the wavenumber-frequency analysis. To predict a low/middle frequency pipe noise, the vibroacoustic analysis method was developed based on Finite Element Method (FEM). And the pipe noise prediction method for the middle/high frequency was developed based on Statistical Energy Analysis (SEA).

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.404-409
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• 2004

A compressor loop pipe is the most important part in a refrigerator from the view of structural vibration and noise. Vibration energy generated from a compressor's inner body is transmitted to the shell and outside through the loop pipe. For this reason it is very important to design a compressor loop pipe. But, for geometrical complexity and dynamic nonlinearity of the loop pipe, analysis and design of the loop pipe is very difficult. So the statistical and experimental methods have to be used for design of this system. The response surface method (RSM) becomes a popular meta-modeling technique f3r the complex system as this loop pipe. As starting point of loop pile's optimization, FEA model and simple experimental model are used instead of the real loop pipe model. After RS model was constructed, using sensitivity-based optimizer performed optimization for the loop pipe. And the moving least square method (MLSM) was applied to reduce the approximation error.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1177-1184
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• 2008

URN(underwater radiated noise) is one of the important performances of the battle ship related to the stealth. The main source of the URN is the structure-borne noise on the hull. And the pipe vibration transmitted to the hull is the main source of the structure-borne noise when the speed of the ship is lower than CIS(cavitation inception speed). In this paper, the vibration isolator(rubber mount) for the pipe system is described in order to reduce the structure-borne noise transmitted to the hull. The vibrations on the sea-water conveying pipes and their supports are measured in order to know how much vibration occurs on those positions. Based on these test results, the improved design of the rubber mount is suggested by the parametric study and is verified numerically with the pipe and hull model.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.7
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• pp.550-556
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• 2002

The vibrational system of this study is consisted of a cantilever pipe conveying fluid. the moving mass upon it and an attacked tip mass. The equation of motion is derived by using Lagrange equation. The influences of the velocity and the inertia force of the moving mass and the velocities of fluid flow in the pipe haute been studied on the dynamic behavior of a cantilever pipe by numerical method. As the velocity of the moving mass increases, the deflection of cantilever pipe conveying fluid is decreased. Increasing of the velocity of fluid flow make the amplitude of cantilever pipe conveying fluid decrease. The deflection of the cantilever pipe conveying fluid is increased by moving masses. After the moving mass passed upon the cantilever pipe, the amplitude of pipe is influenced due to the deflection of pipe tilth the effect of moving mass and gravity.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.5
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• pp.374-379
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• 2002

A new active muffler system has been developed and its superior performance on both noise reduction and engine torque increase is demonstrated with experiment. Main characteristic of the proposed muffler system is the use of destructive interference by transmission path difference of divided exhaust pipes to reduce major exhaust noise components thereby overcoming problems of other active exhaust noise control methods. The exhaust pipe is divided into two sections and joined again downstream. One divided pipe has a sliding mechanism to vary its length, which is controlled to make half wavelength transmission path difference for the major engine rpm frequency. In this system one divided pipe is used to control major rpm frequency and its Harmonics and another pipe is used to control noise component double the frequency of rpm. An after-market tuning muffler, which has very simple internal structure and minimal back pressure, is also installed to remove remaining wideband noise. To make the system to be small enough to be practical, conventional muffler is also installed and used in low rpm range and active muffler is only employed in high rpm range. Noise reduction of the proposed system is comparable to conventional passive muffler. The engine dynamo test has proved the proposed system can recover almost all the torque lost by conventional muffler.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.04a
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• pp.679-680
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• 2011

The Forced vibration characteristics of elastically restrained pipe conveying fluid with the attached mass are investigated in this paper. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by using Hamilton's principle. The effect of attached mass and spring constant on forced vibration of pipe system is studied. Also, the critical flow velocities and stability maps of the valve-pipe system are obtained as each parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.67-71
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• 2003

The propagation characteristics of the impulse wave discharged from the exit of a perforated pipe is investigated through a simple shock tube facility. The pressure histories and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the shock tube experiments, the impulse wave are visualized by a Schlieren optical system for the purpose of understanding its propagation characteristics. The experimental results show that for the near sound field the impulse noise strongly propagates toward to the pipe axis, but for the far sound field the impulse noise uniformly propagates toward to the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. Especially, it is shown that the perforated pipe has a little performance to reduce the impulse noise only for the near sound field

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.3
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• pp.15-21
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• 2003

This experimental study describes the propagation characteristics of the impulse noise emitted from the exit of a perforated pipe attached to the open end of a simple shock tube facility. The pressure amplitudes and directivities of the impulse wave propagating outside from the exit of pipe with several different configurations are measured and analyzed for the range of the incident weak shock wave Mach number between 1.02 and 1.2. In the experiments. the impulse waves are visualized by a Schlieren optical system for the purpose of understanding their propagation characteristics. The results obtained show that for the near sound field the impulse noise strongly propagates toward the pipe axis, but for the far sound field the impulse noise uniformly propagates toward the omnidirections, indicating that the directivity pattern is almost same regardless of the pipe type. For this non-directivity in the far sound field, it is shown that the perforated pipe has little performance to suppress the impulse noise.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.1
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• pp.71-76
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• 2009

In a running blower, there are various exciting forces which can generate noise. The noise of an running industrial fan or blower depends on the structure of a fan, the machining accuracy of each element, and assembled conditions. Many studies have been carried out to reduce the noise of it. In this study, 3-hole buffs are used in pipe of blower to study the influence the number and position of buffs on the noise reduction at inlet and outlet in pipe. Commercial engineering software ANSYS and SYSNOISE were employed to analyze the characteristics and reduction ratio of pressure. It is concluded that optimal position and number of buffs in pipe of blower to show the least reduction ratio of pressure.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.308-311
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• 2005

In this paper, we studied about the effects of the rotating cantilever pipe conveying fluid with a moving mass. The influences of a rotating angular velocity, the velocity of fluid flow and moving mass on the dynamic behavior of a cantilever pipe have been studied by the numerical method. The equation of motion is derived by using the Lagrange's equation. The cantilever pipe is modeled by the Euler-Bemoulli hew theory. When the velocity of a moving mass is constant, the lateral tip-displacement of a cantilever pipe is proportional to the moving mass and the angular velocity. In the steady state, the lateral tip-displacement of a cantilever pipe is more sensitive to the velocity of fluid than the angular velocity, and the axial deflection of a cantilever, pipe is more sensitive to the effect of a angular velocity.