• Title/Summary/Keyword: 난류유동특성

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A flow characteristic of non-newtonian fluid in coutte flow of concentric cylinder (동심원통속의 Coutte flow에 있어서 비 Newton 유체의 유동특성)

  • 권혁칠;이성노;부전유사
    • Journal of the korean Society of Automotive Engineers
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    • v.14 no.3
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    • pp.109-114
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    • 1992
  • The purpose of this study is to experimentally research the effects of polymer additives on turbulent transition of Couette flow between concentric cylinders when outer one is rotating and inner one is at rest; the diameter ratio being 0.2. Aqueous polymer solution generate the degradation phenomena in machine forming work, but this is not effected in about 10 minute at 5ppm. aqueous polymer solution testing. The Reynolds number, referred to the gap distance and rotation velocity of the outer cylinder, of turbulent transition is about 20000 for water flow. In the laminer region, the torque value is as same as theoretical one in the region of low Reynolds number, but becomes high with an increase in the Reynolds number. The polymer additives reduce the Reynolds number for turbulent transtition. In the turbulent region, the torque is remarkably reduced by the polymer additives, soluble polymer take down effect of turbulent transition boundary torque.

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The Structure of the Axisymmetric turbulent Diffusion Flame -( I ) Flow Measurement in Isothermal Field- (재순환 영역이 있는 축대칭 난류확산화염의 구조 -( I ) 비연소 유동장 측정 결과-)

  • 이병무;신현동
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.8 no.4
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    • pp.328-334
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    • 1984
  • 본 연구에서는 기하학적으로는 물론이며 유동 장체가 축대칭이 되고 재순환 영역이 있는 노즐을 제작하여 우선 연구의 1차 단계로서 연소가 없을 경우 시간 평균 유속 및 난류 성분을 레이져 도플러 유속계로 비교적 정밀히 측정한후, 노즐 유체와 주위공기류와의 시간 평균 혼합특성을 구명하기 위하여 가스크로마토그라프에 의하여 농도 분포를 측정, 모델 검토를 위한 기초 데이타 제공과 실험용으로 채용한 노즐류의 구조를 구명하고저 한다. 특히 노즐유체를 수소/질소 혼합기인 경우와 공기를 사용 한 양 경우를 비교, 검토하므로써 부력효과에 대한 평가를 시도하였다.

Centerline Turbulent Characteristics of an Axisymmetric Flow with the Swirl (소용돌이 성분이 있는 축대칭유동의 중심난류 특성)

  • 남경덕;한용운
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.10
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    • pp.2724-2737
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    • 1994
  • The swirl effect on an axisymmetric turbulence has been investigated along its centerline by the hot wire anemometry. Flow facility to generate and conrol the swirl has been built by using the rotating honeycomb and grid. For the case of internal flows, as the strength of the swirl increases the flow tends to be locally isotropic by modifying the radial and the rotational components mainly. In comparison with those of the plain free jet, the decay of the centerline turbulences seems to be delayed substantially even with a slight swirl component.

Turbulence Enhancement Characteristics Analysis of Inclined-Tumbles for Various SCV Configurations (SCV형상별 경사텀블유동의 난류증가 특성 해석)

  • Lee, J.W.;Kang, K.Y.;Choi, S.H.;Park, S.C
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.234-242
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    • 1998
  • It has been demonstrated that the in-cylinder turbulence is enhanced by inclined swirl with a SCV(swirl control valve). The inclined-tumble flow measurement and analysis were performed for various types of intake systems that generated several different combinations of swirl ratio and tumble ratio in the cylinder. Experiments were conducted in a 4-valve optically accessed transparent research engine using a backward-scatter LDV mode under motoring condition at 1,000rpm. The influence of swirl/tumble levels on the characteristics of turbulence was analysed. This study presents experimental results of the inclined-tumble flow structure, including the flow motion phenomena, angular momentum and turbulence intensity.

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Fluid and Heat Transfer Characterization of Surfactant Turbulent Pipe Flows (계면활성제가 첨가된 관내 난류의 열유동 특성에 관한 고찰)

  • Shin, Kwang-Ho;Yoon, Hyung-Kee;Chang, Ki-Chang;Ra, Ho-Sang
    • Proceedings of the SAREK Conference
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    • 2006.06a
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    • pp.982-987
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    • 2006
  • The fluid mechanics and heat transfer of surfactant turbulent pipe flows are characterized with particular emphasis on the effects of surfactant concentration and solution temperature on drag reduction and heat transfer reduction. The test fluids are the surfactant solutions of DR-IW616 supplied by Akzo Nobel Chemical in concentration of $100{\sim}3000ppm$. The solution temperatures studied are $5^{\circ}C$ to $50^{\circ}C$. The critical values of surfactant concentration and solution temperature are clearly identified for drag reduction phenomena.

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A Study on Turbulence Flow Characteristics at the Spark Plug Location in S.I. Engine (가솔린기관의 점화플러그 위치에서 난류유동 특성에 관한 연구)

  • 정연종;조규상;김원배
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.9
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    • pp.2423-2430
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    • 1994
  • Several factors of the efficient combustion process are shape of combustion chamber, position of spark plug, turbulence flow and so on. the shape of combustion chamber and position of spark plug are constrained to geometrically, and then it could not make a change the shape easily. But the turlence flow in combustion chamber have a great influence on combustion phenomena, and which is much easier to control relatively. And since characteristics of turbulence flow would be very important to the stability of combustion and performances, This study is also essential to future engine-low emission and lean burn engine. This paper shows that the visualization of the turbulence flow of single cylinder engine by using 2way, $45^{\circ}$ inclined and 2 channel hot wire probe through the park plug hole. We also study the characteristics of turbulence flow by means of ensemble averaged mean velocity, turvulence intensity and integral length scale.

Numerical Study of Turbulence Modeling for Analysis of Combustion Instabilities in Rocket Motor (로켓엔진의 연소 불안정 해석을 위한 난류 모델링의 수치적 연구)

  • 임석규;노태성
    • Journal of the Korean Society of Propulsion Engineers
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    • v.6 no.2
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    • pp.75-84
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    • 2002
  • A numerical analysis of unsteady motion in solid rocket motors with a nozzle has been conducted. The numerical formulation including modified $\kappa$-$\varepsilon$ turbulence model treats the complete conservation equation for the gas phase and the one-dimensional equations in the radial direction for the condensed phase. A fully coupled implicit scheme based on a dual time-stepping integration algorithm has been adopted to solve the governing equations. After obtaining a steady state solution, pulse and periodic oscillations of pressure are imposed at the head-end to simulate acoustic oscillations of a travelling-wave motion in the combustion chamber. Various steady and unsteady state features in the combustion chamber of a rocket motor has been analyzed as results of numerical calculations.

Comparison of Algorithm & Turbulence Modelling for Calculation of Compressor Cascade Flows (압축기 익렬 유동해석을 위한 알고리즘과 난류 모델의 비교 연구)

  • 김석훈;이기수;최정열;김귀순;임진식;김유일
    • Journal of the Korean Society of Propulsion Engineers
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    • v.4 no.4
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    • pp.59-69
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    • 2000
  • A numerical analysis based on two-dimensional, incompressible and compressible Navier-Stokes equations was carried out for double circular arc compressor cascade and the results are compared with available experimental data. The incompressible code based on SIMPLE algorithm adopts pressure weighted method and hybrid scheme for the convective terms. The compressible code with preconditioning method involves a upwind-biased scheme for the convective terms and LU-SGS scheme for temporal integration. Several turbulence models are evaluated by computing the turbulent viscous flows; Baldwin-Lomax, standard $\kappa$ -$\varepsilon$, $\kappa$ -$\varepsilon$ Lam. Bremhorst, standard $\kappa$-$\omega$, $\kappa$ -$\omega$ SST model.

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A Study on Grid Dependencies of the Numerical Solutions for Ship Viscous Flows (배주위 점성유동장에 대한 수치해의 격자의존성에 관한 연구)

  • Kang, K.J.;Lee, S.H.
    • Journal of the Society of Naval Architects of Korea
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    • v.31 no.4
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    • pp.58-65
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    • 1994
  • It is very important to understand characteristics of solution due to the variation of computational grid sizes, especially when turbulence model not incorporating wall-function is used. The present paper performs numerical investigation on the grid dependency of numerical solution for three dimensional turbulent flow field around a ship. In the present study a finite volume method with a modified sub-grid scale turbulence model and a numerically constructed non-orthogonal curvilinear coordinate system capable of conforming complex ship geometries are used. Numerical studies are then performed for a mathematical Wigley hull and the Series 60, $C_B=0.8$ hull forms. The results for various grid sizes are compared with each other and with measured data to show grid dependencies of numerical solutions.

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Study on the statistical turbulence characteristics of cross jets in the cylinder by on-line computer system (온라인 컴퓨터 시스템에 의한 실린더내 충돌분류의 통계학적 난류특성 연구)

  • 노병준;박종호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.876-891
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    • 1988
  • This study was carried out to investigate the mixing flow of a turbulent cross jet in a cylindrical chamber. A study on the turbulent mixing flow of a cross jet at 45.deg. with respect to each other in the free atmospheric condition was conducted before this study and has given us some fundamental experimental results. Present data have been analyzed and compared with semi-empirical equations for a round and a plane jets. Interests on this kind of cross jets (flows) have been increasing during the past several years for the purpose of the analysis of mixing flows and their applications. In this study, a turbulent cross jet of air in a cylindrical chamber has been conducted and the turbulent characteristics in the mixing region have been analyzed experimentally. The experimental data were discussed by comparing with the semi-empirical equations of Hinze and Gortler. From the experimental curve, the semi-empirical equations of mean velocities and Reynolds stresses have been derived. Three dimensional data acquisitions and the statistical treatments of turbulence characteristics were carried out by on-line computer measurement system connected with the constant temperature type 2-channel hot-wire anemometer system.