• Title/Summary/Keyword: High Speed Impulsive Noise

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Passive control of unsteady compression wave using vertical bleed ducts (수직갱을 이용한 터널내 비정상 압축파의 피동제어)

  • Kim, Hui-Dong;Setoguchi, Toshiaki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.9
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    • pp.1095-1104
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    • 1997
  • When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. For the purpose of the impulsive noise reduction, the present study investigated the effect of a vertical bleed duct on the compression wave propagating into a model tunnel. Numerical results were obtained using a Piecewise Linear Method and testified by experiment of shock tube with an open end. The results showed that the vertical bleed duct reduces the maximum pressure gradient of compression wave front by about 30 percent, compared with the straight tunnel without the bleed duct. As the width of the vertical bleed duct becomes larger, reduction of the impulsive noise is expected to be greater. However the impulsive noise is independent of the height of the vertical bleed duct.

Experimental study of compression waves propagating porous walls (다공벽을 전파하는 압축파의 실험적 연구)

  • Kim, Hui-Dong;Setoguchi, Toshiaki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.12
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    • pp.4036-4043
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    • 1996
  • When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates along the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. In the purpose of the impulsive noise reduction, the present study tested the effect of porous walls on the compression wave propagating into a model tunnel. Experimental results were obtained using a shock tube with an open end. The results showed that the cavity/porous wall is very effective for the compression wave with a large nonlinear effect. The porosity of 30% is most effective for attenuation and pressure gradient reduction of the compression wave front. Also the impulsive noise reduction increases with increasing the length and height of the cavity, compared with the tunnel equivalent diameter.

Experimental study on reduction of impulsive noise generating at exit of high-speed railway tunnel (고속철도 터널출구에서 발생하는 충격성 소음의 저감을 위한 실험적 연구)

  • Kim, Hui-Dong;Setoguchi, Toshiaki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.20 no.7
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    • pp.2375-2385
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    • 1996
  • As a compression wave is emitted from a duct, an impulsive wave generates and causes an impulsive noise that is at present a serious environmental noise pollution. In order to clarify the acoustic characteristics of the noise and to reduce their pressure levels, a series of model experiments were conducted on the impulsive waves emitted from an open end of a shock tube. The impulsive waves with various intensities were obtained by controlling the operation pressure ratio of the shock tube. Various kinds of silencers such as the exit boxes with baffle plates, were applied to the duct exit to reduce the impulsive noises. The effects of geometry of silencers and shock Mach number on the noise reduction were clarified. From the measurements of sound pressure level, it was found that installing the baffle plate into the exit box is effective in lowering the noise level at far fields, and that the recommendable geometries of silencer are L/D=1, H/D=1 and H/D=0.75.

Numerical Study of Compression Waves Propagating Through Porous Walls (다공벽을 전파하는 압축파에 관한 수치해석적 연구)

  • Kim, Hui-Dong;Setoguchi, Toshiaki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.11
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    • pp.1403-1412
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    • 1997
  • When a high-speed railway train enters a tunnel, a compression wave is generated ahead of the train and propagates through the tunnel, compressing and accelerating the rest air in front of the wave. At the exit of the tunnel, an impulsive wave is emitted outward toward the surrounding, which causes a positive impulsive noise like a kind of sonic boom produced by a supersonic aircraft. With the advent of high-speed train, such an impulsive noise can be large enough to cause the noise problem, unless some attempts are made to alleviate its pressure levels. In the purpose of the impulsive noise reduction, the present study calculated the effect of porous walls on the compression wave propagating into a model tunnel. Two-dimensional unsteady compressible equations were differenced by using a Piecewise Linear Method. Calculation results show that the cavity/porous wall system is very effective for a compression wave with a large nonlinear effect. The porosity of 30% is most effective for the reduction of the maximum pressure gradient of the compression wave front. The present calculation results are in a good agreement with experimental ones obtained previously.

Finite Element Analysis of High-speed Rotating Disks Considering Impulsive Loading by the Clearance and Contact (간격 및 접촉에 의한 충격하중을 고려한 고속 회전 디스크의 유한요소 해석)

  • Lee, Kisu;Kim, Yeong Sul;So, Jae Uk
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.1
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    • pp.45-53
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    • 2014
  • For the time integration solution of the impulsive dynamic contact problem of high-speed rotating disks formulated by the finite element technique, the velocity and acceleration contact constraints as well as the displacement contact constraint are imposed for the numerical stability without spurious oscillations. The solution of the present technique is checked by the numerical simulation using the concentric high-speed rotating disks with the clearance and impulsive loading. It is shown that the almost steady state solution agrees with the corresponding analytical solution of the elasticity and that the differentiated constraints are crucial for the numerical stability of such high-speed contact problems of the disks under impulsive loading.

Numerical study on the interaction between unsteady compression and unsteady expansion wave (비정상 압축파와 비정상 팽창파의 간섭에 관한 수치해석적 연구)

  • Kim, Hui-Dong;Setoguchi, Toshiaki
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.11
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    • pp.1413-1421
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    • 1997
  • A new control method to alleviate the impulsive noise at the exit of high-speed railway tunnel was applied to the compression wave at the entrance of the tunnel. This method uses the interaction phenomenon of unsteady expansion wave and unsteady compression wave. Unsteady expansion wave was assumed to be made instantaneously by the simple theory of shock tube. Total Variation Diminishing method was employed to solve the axisymmetric unsteady compressible flow field with a specified compression wave. Numerical results show that the maximum pressure gradient of the propagating compression wave decreases with increase of the wave length of the unsteady expansion wave. It is found that the impulsive noise reduction can be obtained when the unsteady expansion wave with a large wave length is emitted just before the train enters the tunnel. The present results give the possibility to reduce the impulsive noise at the exit of tunnel.

BLADE PLANFORM OPTIMIZATION FOR HSI NOISE REDUCTION OF HELICOPTER (헬리콥터의 고속충격소음 감소를 위한 블레이드 평면형상 최적화)

  • Chae, Sang-Hyun;Yang, Choong-Mo;Jung, Shin-Kyu;Aoyama, Takashi;Obayashi, Shigeru;Yee, Kwang-Jung
    • Journal of computational fluids engineering
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    • v.14 no.1
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    • pp.53-61
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    • 2009
  • The objective of this research is to design blade planform to reduce high speed impulsive(HSI) noise from a non-lifting helicopter rotor using CFD method and optimization techniques. As for the aero-acoustic analysis, CFD technique for aerodynamic analysis and Kirchhoff's method for the acoustic analysis were used. As for the optimization method, Kriging-based genetic algorithm(GA) model as a high-fidelity optimization method was chosen. Design variables and constraints are determined for arbitrary blade planform. The result shows that the optimized blade planform with high swept-back and taper ratio can reduce HSI noise by suppressing generation of the strong shock wave on blade surface and propagation of the noise to the farfield flow region.

Numerical Simulation for the Effect of Entrance Hood on Pressure of High Speed Railway Tunnel (입구후드가 고속열차 터널의 압력에 미치는 영향에 대한 수치해석 적 연구)

  • 김동현;이재범;양신추;이희성;오일근
    • Proceedings of the KSR Conference
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    • 1999.05a
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    • pp.406-413
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    • 1999
  • A compression wave is generated by the high speed train which enters a tunnel, and it propagates along the tunnel. When the compression wave emerges from the exit of the tunnel, it causes an impulsive noise, and the strength of the impulsive noise depends on the pressure gradient of the first compression wave. So it needs to reduce the pressure gradient for the minimization of impulsive noise. The entrance hood is used for the reduction of the pressure gradient. In the present study, the pressure transients were numerically calculated for three shapes of hood, In order to validate the numerical simulation, the pressure and pressure gradient were compared with the experimental data of moving model rig. The calculation results won well agreed with the experimental data, and also showed that the hood had an effect on the pressure gradient of the tunnel inside.

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Aerodynamic Noise Analysis Using the Permeable Surface for UH-1H Rotor Blade in Hovering Flight Condition (UH-1H 로터 블레이드의 제자리 비행 시 투과면을 이용한 원방 소음 해석)

  • Kim, Ki Ro;Park, Min Jun;Park, Soo Hyung;Lee, Duck Joo;Park, Nam Eun;Im, Dong Kyun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.5
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    • pp.376-384
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    • 2018
  • The aerodynamic far-field noise was computed by an acoustic analogy code using the permeable surface for the UH-1H rotor blade in hover. The permeable surface surrounding the blade was constructed to include the thickness noise, the loading noise, and the flow noise generated from the shock waves and the tip vortices. The computation was performed with compressible three-dimensional Euler's equations and Navier-Stokes equations. The high speed impulsive noise was predicted and validated according to the permeable surface locations. It is confirmed that the noise source caused by shock waves generated on the blade surface is a dominant factor in the far-field noise prediction.

Determination of Channel Capacity Bounds of Narrow Band ISDN Subscriber Line in the Presence of Impulsive Noise (임펼스성 잡음이 있을때 협대역 ISDN 가입자 전송로의 통신로 용량 한계 결정)

  • Lee, Jong-Heon;Sung, Tae-Kyung;Chin, Yong-Ohk
    • Proceedings of the KIEE Conference
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    • 1987.07b
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    • pp.854-858
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    • 1987
  • This paper considers impulsive noise which produce burst error in high speed(approx.160Kbps) data transmission like ISDN(Integrated Servise Digital Network) using PSTN(Public Switching Telephone Network). To begin with, we obtains the transfer function of subscriber line to calculate the variation of bandwidth when the gain of receiver is fixed and channel capacity of non-gaussian channel in upper-and lower bound, and evaluates the transmission capability. In this paper compares channel capacity bounds which obtains when probability density function of impulsive noise is Laplacian distribution function with impulsive noise generated by waveform synthesier.

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