• Title/Summary/Keyword: 초음속 제트소음

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Numerical Simulation of the Screech Phenomenon in a Supersonic Jet (수치계산에 의한 초음속 제트에서의 스크리치 현상 해석)

  • Kim, Yong-Seok;Kim, Sung-Cho;Kim, Jeong-Soo
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2007.04a
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    • pp.329-334
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    • 2007
  • An axisymmetric supersonic jet screech in the Mach number range from 1.07 to 1.2 is numerically simulated. The axisymmetric mode is the dominant screech mode for an axisymmetric jet. The Reynolds-averaged Navier-Stokes equations in the conjunction with modified Spalart-Allmaras turbulence model are employed. A high resolution finite volume essentially non-oscillatory(ENO) schemes are used along with nonreflecting characteristic boundary conditions that are crucial to screech tone computations to accurately capture the sound waves, shock-cell structures, unsteady shock motions and large-scale instability waves.

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로켓 음향 환경의 특성에 대한 연구

  • Park, Soon-Hong;Yi, Yeong-Moo
    • Aerospace Engineering and Technology
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    • v.1 no.2
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    • pp.91-104
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    • 2002
  • Jet noise of propulsion systems is major source of acoustic loads of launch vehicles and sounding rockets. The investigation of characteristics of jet noise is inevitable for successful missions. In this paper, the mechanism of generation of acoustic loads due to jet noise was investigated. The major parameters that change the characteristics of acoustic loads were also suggested so that effects of the parameters could be investigated. The temporal and spatial characteristics of acoustic loads of KSR-III was demonstrated. The results show that the maximum value of the acoustic loads is found in the octave bands whose center frequencies are 250 Hz and 500 Hz. Finally, the methods and the facilities for the further investigation of acoustic loads were proposed.

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Effect of Sound-Absorbing Materials on the Characteristics of Supersonic Jet Noise (흡음재가 초음속 제트의 소음특성에 미치는 영향)

  • Gwak, Jong-Ho;Kweon, Yong-Hun;Aoki, Toshiyuki;Kim, Heuy-Dong
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.1499-1504
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    • 2004
  • The effects of absorbing materials on the characteristics of supersonic jet noise were experimentally investigated using a convergent-divergent nozzle with a design Mach number of 2.0. Overall sound pressure levels (OASPL) and noise spectra were obtained at far-field locations. Schlieren optical system was used to visualize the flow-fields of supersonic jets. In order to investigate the effect of absorbing materials, baffle plates of different materials (metal, grass wool and polyurethane foam) were installed at the exit of the nozzle. Experiment was carried out over a wide range of nozzle pressure ratios from 2.0 and 18.0, which corresponds to over- and under-expanded conditions. The results obtained show that the screech tone amplitude and the overall sound pressure level reduce by using the baffle plates of absorbing materials, compared with the metal baffle plate. It is also found that the characteristics of supersonic jet noise are strongly dependent on the size of baffle plate.

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Effect of Mesh Screen Device on Over-Expanded Supersonic Jet Noise (메쉬 스크린 장치가 과팽창 초음속 제트소음에 미치는 영향)

  • Kweon, Yong-Hun;Kim, Jae-Hyung;Lim, Chae-Min;Aoki, Toshiyuki;Kim, Heuy-Dong
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.3150-3155
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    • 2007
  • This paper describes an experimental work to investigate the effect of mesh screen device on the jet structure and acoustic characteristics of over-expanded supersonic jet. The mesh screen device is placed into the supersonic jet stream. In order to perturb mainly the initial jet shear layer, the hole is perforated in the central part of the mesh screen. The diameter of the perforated hole and the location of mesh screen device are varied. A Schlieren optical system is used to visualize the flow fields of supersonic jet without and with the mesh screen device. Pitot pressure measurement is carried out to obtain the pressure distribution in the jet flow. Acoustic measurement also is performed to obtain the OASPL and noise spectra. The results obtained show that the jet structure and the jet noise control effectiveness is strongly dependent upon the diameter of the perforated hole and the location of the mesh screen device in the jet stream. Provided that the mesh screen device is placed at the location to perturb effectively the initial shear layer, the present control method is effective in suppressing the supersonic jet noise.

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Control of the Supersonic Jet Noise Using a Wire Device (와이어 장치를 이용한 초음속 제트소음의 제어)

  • Kweon Yong Hun;Lim Chae Min;Aoki Toshiyuki;Kim Heuy Dong
    • 한국가시화정보학회:학술대회논문집
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    • 2004.11a
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    • pp.64-67
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    • 2004
  • The present study describes an experimental work to reduce supersonic jet noise using a control wire device that is placed into the supersonic jet stream. The jet pressure ratio is varied to obtain the supersonic jets which are operated in a wide range of over-expanded to moderately under-expanded conditions. The wire device is composed of long cylinders with a very small diameter. X-type wire device is applied to control the supersonic jet noise, and its location is varied to investigate the effect of the control wire device on supersonic jet noise. A high-quality Schlieren optical system is used to visualize the flow field of supersonic jet with and without the control wire device. Acoustic measurement is performed to obtain the overall sound pressure level and noise spectra. The results obtained show that the present wire device destroys the shock-cell structures, reduces the shock strength, and consequently leading to a substantial suppression of supersonic jet noise.

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Design and Manufacturing of the Diffuser with Water Injection for the Solid Rocket Motor Noise Reduction (고체추진기관용 물분사 소음디퓨저의 설계 및 제작)

  • Lee, Jeong-Yeol;Lee, Je-Hyung;Lee, Sung-Woong;Ko, Hyun;Cho, Yong-Ho
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2011.11a
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    • pp.299-302
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    • 2011
  • In the supersonic jet of a solid rocket motor, various noise is investigated. The purpose of this study is to attain and evaluating a design and manufacturing technique of the SRM noise reduction. In this study, the water is injected into the supersonic jet of the SRM to reduce the noise. Furthermore, the diffuser and stack are installed to suppress the SRM noise. Through the SRM ground tests, the noise is reduced approximately 20dBA with application of the diffuser/stack with water injection.

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Study of Screened Supersonic Jet Flow Fields (스크린 설치에 따른 초음속 제트유동 변화에 관한 연구)

  • Lee, Yeol
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.8
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    • pp.92-98
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    • 2005
  • Screen can provide any disturbed resistance that affects the change in characteristics of turbulence, velocity and pressure distributions of the flow field, and thus it has been widely used to control the flow. Some previous related studies for compressible flows have limitations such as, considering relatively low-Mach-number flows in the range of 0.3 ∼ 0.7, and not observing the detailed shock structures of the flow fields. An experimental study on highly compressible axi-symmetric supersonic jet flow fields behind wire-gauze screen has thus been carried out. Continuous/instantaneous flow images by Schlieren flow- visualization technique and the information of Pitot pressure/flow-noise measurements of the flow field behind the screen for various jet expansion conditions have been obtained. Effects of various porosity and inclination angles of the screen at the nozzle exit have also been investigated, and the experimental results have been compared to the case with no screen installed.

Numerical Investigation on the Mechanism of Mode Transition in Axi-symmetric Supersonic Jet Screech (축대칭 초음속 제트에서 스크리치 모드 전이현상의 수치적 연구)

  • Bin, Jong-Hoon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.38 no.8
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    • pp.790-797
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    • 2010
  • Mode transition of the axi-symmetric screech tone in the low supersonic Mach number range from 1.0 to 1.20 is numerically analyzed. The axi-symmetric Navier-Stokes equations and the k-e turbulence model are solved in the cylindrical coordinate system. The dispersion-relation-preserving(DRP) scheme is applied for space discretization and the optimized four levels marching method are used for time integration. At low supersonic Mach numbers with an axi-symmetric A1 mode in the simulation, it is shown that acoustic propagation due to the nonlinear effects is seen in the lateral direction and the screech tone frequency is the same as the vortex passing frequency due to the generation of intense large-scale vortical motions.

Numerical Analysis of the Mach Wave Radiation in an Axisymmetric Supersonic Jet (축대칭 초음속 제트에서의 마하파 방사에 관한 수치적 연구)

  • Kim, Yong-Seok;Lee, Duck-Joo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.71-77
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    • 2000
  • An axisymmetric supersonic jet is simulated at a Mach number of 1.5 and a Reynolds number of $10^5$ to identify the mechanism of sound radiation from the jet. The present simulation is performed based on the high-order accuracy and high-resolution ENO(Essentially Non-Oscillatory) schemes to capture the time-dependent flow structure representing the sound source. In this simulation, optimum expansion jet is selected as a target, where the pressure at nozzle exit is equal to that of the ambient pressure, to see pure shear layer growth without effect of change in jet cross section due to expansion or shock wave generated at nozzle exit. Shock waves are generated near vortex rings, and discernible pressure waves called Mach wave are radiated in the downstream direction with an angle from the jet axis, which is characteristic of high speed jet noise. Furthermore, vortex roll-up phenomena are observed through the visualization of vorticity contours.

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