• Title, Summary, Keyword: 팽창파

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Experimental Study of the Internal/external Pressure Variation of TTX Travelling through a Tunnel (한국형 틸팅차량의 터널 주행시 실내/외 압력변화에 대한 실험적 연구)

  • Yun, Su-Hwan;Kwak, Min-Ho;Lee, Dong-Ho;Kwon, Hyeok-Bin;Ko, Tae-Hwan
    • Journal of the Korean Society for Railway
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    • v.12 no.2
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    • pp.309-314
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    • 2009
  • When a train enters into a tunnel, a compression wave is generated by a front nose and a expansion wave is generated by a rear tail respectively. The interaction between pressure waves and the train makes the internal and external pressure of the train change dramatically. In this paper, we had measured the internal and external pressure variations of TTX and analyzed the pressure variations as the tunnel length. Also, the rate of internal pressure variations were investigated with the current airtight condition of TTX. In short tunnels, the internal and external pressure variation were not large because the superposition of pressure waves was not happened. In long tunnels, however, the rapid and large pressure variations were shown because of the superpositions between the same sort of pressure waves, such as expansion wave and expansion wave or compression wave and compression wave. In specific length tunnels, the pressure variation and the pressure variation rates were largely lessened because the compression wave and expansion wave were superposed.

A Study on Aerodynamic Characteristics of Busemann Type Supersonic Biplane (부즈만 형의 초음속 복엽항공기에 대한 공력 특성 연구)

  • Mun, Chan-Ung;Kim, Hun;Yu, Gi-Wan
    • Proceeding of EDISON Challenge
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    • pp.425-430
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    • 2013
  • 본 연구에서 전산유체해석 프로그램인 EDISON_CFD를 이용하여 차세대 항공기 날개 형상으로 각광받고 있는 초음속 비행조건을 갖는 Busemann 형식의 복엽기 형상에 대한 공력특성을 연구하였다. 날개는 압축성 조건에서 2차원 에어포일로 간략화 하여 모델링하였으며, 마하수에 따라 발생하는 충격파와 팽창파의 상호작용을 통한 소닉붐의 감소 형태를 분석해 보고, 마하수에 따른 항력계수를 얻어내었으며, 익형과 항력계수, 소닉붐의 상관관계를 분석하여 초음속항공기에서 복엽기 형상이 가지는 장단점에 대하여 연구하였다.

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수직평판에 충돌하는 축대칭 초음속 제트의 수치 해석

  • 신완순;이택상;박종호;김윤곤
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.20-20
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    • 2000
  • 초음속 과소팽창 제트는 베럴충격파(Barrel shock), 팽창파(Expansion fan), 반사충격파(Reflected shocks), 마하디스크(Mach disc), 그리고 제트경계면(Exhaust-gas Jet boundary)로 이루어지는 여러 충격파 셀(Shock ceil)의 유동 형태를 나타난다. 이러한 초음속 과소팽창 제트가 수직 평판에 충돌하면 초음속 자유 제트와는 다른 변형된 유동장이 형성된다.

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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.

A Numerical Study on Strut-Placed Supersonic Flow in Annulus Flowfield (스트럿트가 있는 초음속 환형유동장에 대한 수치적 연구)

  • Park Hee Jun;Joo Won Goo
    • 한국전산유체공학회:학술대회논문집
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    • pp.53-63
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    • 2002
  • In this numerical approach, strut-placed supersonic annular flow is examined. The geometrical variations of strut cause strong influence on flowfield structures. The geometrical variations are as follows, swept effect, attack angle effect, variation of leading edge shape. These changed features such as velocity structure, pressure structure, shock-boundary layer interaction are compared and analyzed according to each geometrical configuration.

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A Computational Study on the Shock Structure and Thrust Performance of a Supersonic Nozzle with Overexpanded Flow (과대팽창이 발생하는 초음속노즐의 충격파 구조와 추력성능에 대한 수치적 연구)

  • Bae, Dae Seok;Choi, Hyun Ah;Kam, Ho Dong;Kim, Jeong Soo
    • Journal of the Korean Society of Propulsion Engineers
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    • v.18 no.4
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    • pp.1-8
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    • 2014
  • Overexpanded flow of an axisymmetric thruster nozzle is numerically simulated to investigate effects of nozzle pressure ratio (NPR) on the shock structure and thrust performance. The Reynolds-averaged Navier-Stokes equations with k-${\omega}$ SST turbulence model are solved utilizing FLUENT solver. As the NPR is raised, thrust performance monotonically increases with the shock structure and flow-separation point being pushed toward the nozzle exit. It is also discussed that the flow structure at nozzle-exit plane which is immediately affected by a position of nozzle-interior shocks and expansion waves, has strong influence upon the thrust performance of thruster nozzle.

A Study on the Transitional Shock Separation Patterns in an Over-Expanded Nozzle (과팽창 노즐에서 발생하는 충격파 박리 패턴의 천이에 관한 연구)

  • Lee, Jong-Sung;Lijo, Vincent;Kim, Heuy-Dong
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.3
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    • pp.9-15
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    • 2010
  • Numerical investigation was carried out on axisymmetric over-expanded rocket nozzle to predict flow fields of transitional shock separation patterns. The unsteady, compressible N-S equations with k-$\omega$ SST for turbulence model closure were solved using a fully implicit finite volume scheme. Computed results were in good agreement with previous experimental works. It was found that strong side-loads were generated during the transition of RSS to FSS due to the development of a vortex ring in the inviscid jet core region. Hysteresis phenomenon exhibited by the shock-separation patterns was also found during the start-up and shut-down processes.

An Experimental Study of Supersonic Underexpanded Jet Impinging on an Inclined Plate (경사 평판에 충돌하는 초음속 과소팽창 제트에 관한 실험적 연구)

  • 이택상;신완순;이정민;박종호;윤현걸;김윤곤
    • Journal of the Korean Society of Propulsion Engineers
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    • v.3 no.4
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    • pp.67-74
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    • 1999
  • Problems created by supersonic jet impinging on solid objects or ground arise in a variety of situations. For example multi-stage rocket separation, deep-space docking, V/STOL aircraft, jet-engine exhaust, gas-turbine blade, terrestrial rocket launch, and so on. These impinging jet flows generally contain a complex structures. (mixed subsonic and supersonic regions, interacting shocks and expansion waves, regions of turbulent shear layer) This paper describes experimental works on the phenomena (surface pressure distribution, flow visualization) when underexpanded supersonic jets impinge on the perpendicular, inclined plate using a supersonic cold-(low system. The used supersonic nozzle is convergent-divergent type, exit Mach number 2, The maximum on the plate when it was inclined was much larger than perpendicular plate, owing to high pressure recoveries through multiple shocks. Surface pressure distribution as to underexpanded ratio showed similar patterns together.

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앞전에서의 팽창파를 이용한 양항비의 개선에 대한 연구

  • Yun, Yeong-Jun
    • Proceeding of EDISON Challenge
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    • pp.19-22
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    • 2016
  • Leading edge thrust is generally caused by passing air flow from lower to upper surface and it is required to have sufficient angle of attack for notable leading edge thrust. To produce leading edge thrust at low angle of attack, utilizing expansion wave accompanying low pressure is able to be a solution. Fore structure changes the direction of flow, and this flow passes the projected edge. As a result, from a perspective of the edge, it is able to have high angle of attack, and artificial expansion wave is generated. This concept shows 9.48% increase of L/D in inviscid flow, at Mach number 1.3 and angle of attack $1^{\circ}$ in maximum, and this model shows the 3.98% of increasement at angle of attack $2^{\circ}$. Although advantage of the artificial expansion wave decreased as angle of attack increase, it shows the possibility of aerodynamical improvement with artificial expansion wave.

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A Study on the heat transfer characteristics of a normal axisymmetric under-expanded impinging jet on a surface (수직 축대칭 과소팽창 충돌 제트의 표면 열전달 특성 연구)

  • Yu, Man-Sun;Kim, Byung-Gi;Cho, Hyung-Hee;Hwang, Ki-Young;Bae, Ju-Chan
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.8
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    • pp.84-91
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    • 2005
  • An experimental investigation has been carried out to examine heat-transfer characteristics of an axisymmetric, under-expanded, sonic jet impinging on a flat plate and the local measurement of surface pressures and heat transfer coefficients on a plate have been achieved together with a visualization test of shock structure in a jet. Heat transfer coefficients on a plate have been found to be changed significantly depending on the under-expansion ratio as much as the nozzle-to-plate distance. These phenomena could be explained by the wall pressure measurement and the shock visualization.