• 제목/요약/키워드: dimensionless

검색결과 1,064건 처리시간 0.023초

Numerical Analysis for Unsteady Thermal Stratified Turbulent Flow in a Horizontal Circular Cylinder

  • Ahn, Jang-Sun;Ko, Yong-Sang;Park, Byeong-Ho;Youm, Hag-Ki;Park, Man-Heung
    • Nuclear Engineering and Technology
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    • 제28권4호
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    • pp.405-414
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    • 1996
  • In this paper, the unsteady 2-dimensional turbulent flow model for thermal stratification in a pressurizer surge line of PWR plant is proposed to numerically investigate the heat transfer and flow characteristics. The turbulence model is adapted to the low Reynolds number K-$\varepsilon$ model (Davidson model). The dimensionless governing equations are solved by using the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The results are compared with simulated experimental results of TEMR Test. The time-dependent temperature profiles in the fluid and pipe nil are shown with the thermal stratification occurring in the horizontal section of the pipe. The corresponding thermal stresses are also presented. The numerical result for thermal stratification by the outsurge during heatup operation of PWR shows that the maximum dimensionless temperature difference is about 0.83 between hot and cold sections of pipe well and the maximum thermal stress is calculated about 322MPa at the dimensionless time 28.5 under given conditions.

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RADIATION EFFECTS ON MHD BOUNDARY LAYER FLOW OF LIQUID METAL OVER A POROUS STRETCHING SURFACE IN POROUS MEDIUM WITH HEAT GENERATION

  • Venkateswarlu, M.;Reddy, G. Venkata Ramana;Lakshmi, D. Venkata
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • 제19권1호
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    • pp.83-102
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    • 2015
  • The present paper analyses the radiation effects of mass transfer on steady nonlinear MHD boundary layer flow of a viscous incompressible fluid over a nonlinear porous stretching surface in a porous medium in presence of heat generation. The liquid metal is assumed to be gray, emitting, and absorbing but non-scattering medium. Governing nonlinear partial differential equations are transformed to nonlinear ordinary differential equations by utilizing suitable similarity transformation. The resulting nonlinear ordinary differential equations are solved numerically using Runge-Kutta fourth order method along with shooting technique. Comparison with previously published work is obtained and good agreement is found. The effects of various governing parameters on the liquid metal fluid dimensionless velocity, dimensionless temperature, dimensionless concentration, skin-friction coefficient, Nusselt number and Sherwood number are discussed with the aid of graphs.

티모센코 회전축을 따라 움직이는 질량의 진동해석 (Vibration Analysis of a Moving Mass Travelling on the Timoshenko Rotating Shaft)

  • 박용석
    • 한국산학기술학회논문지
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    • 제9권4호
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    • pp.859-864
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    • 2008
  • 티모센포 회전축을 따라 이동하는 이동질량과의 동적상호작용에 관한 연구가 수행되었다. 이동질량의 속력이 티모센코축의 회전속도와 연계된 구속조건식을 도출하였다. 티모센코의 보 이론를 활용하여 시스템의 무차원방정식이 유도되었다. 이동질량의 속력을 포함하는 티모센코 축의 회전속도, 레일리히 계수, 축방향 압축력 등 다양한 무차원 변수들의 영향에 따른 회전축의 처짐과 주파수응답에 대한 해석이 수행되어졌다.

원판증발기를 가진 회전형 히트파이프에서 액막두께가 전열에 미치는 영향 (The Effect of Film Thicknesses on Heat Transfer in a Rotating Heat Pipe with the Disc Evaporator)

  • 권순석;장영석;유병욱
    • 대한기계학회논문집
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    • 제18권6호
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    • pp.1572-1581
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    • 1994
  • Heat transfer characteristics in a rotating heat pipe with evaporator of the rotating disc and the condenser of the screwed groove is investigated by numerical method for various dimensionless film thicknesses, Re, C_{p}{\Delta}T/h_{fg}$, rotational speed and working fluids. The temperature difference between evaporator wall and vapor increases a little, but the temperature difference between condenser wall and vapor decreases rapidly as Re increases. As the dimensionless film thickness decreases, the temperature difference of evaporator and condenser decreases. As the rotational speed increases, the temperature difference between evaporator wall and vapor increases but the temperature difference between condenser wall and vapor decreases. The Nusselt number can be shown as a function of dimensionless film thickness and Re, that is $Nu=0.963\cdot(\delta^{-1}(\omega/\vpsilon)^{-1/2}{\cdot}Re^{0.5025})$.

채널 유동에서 점성이 단일 입자 혼합 유동의 suspension에 미치는 영향 (Effect of Fluid Viscosity on the Suspension of a Single Particle in Channel Flow)

  • 최형권
    • 대한기계학회논문집B
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    • 제33권3호
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    • pp.194-200
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    • 2009
  • Suspension of a single solid particle in a channel flow with a constant pressure gradient is studied numerically. The interaction of a circular particle with a surrounding Newtonian fluid is formulated using a combined formulation. Numerical results are presented using two dimensionless variables: the sedimentation Reynolds number and the generalized Froude number. From the present results, it has been shown that a solid particle is suspended at a smaller generalized Froude number as the viscosity of the surrounding fluid increases. The time taken for equilibrium position is found to be smaller as fluid viscosity increases when both : the sedimentation Reynolds number and the generalized Froude number are the same while, at the same situation, the dimensionless time taken for equilibrium position is to be nearly the same regardless of fluid viscosity when a dimensionless time variable is introduced

단면 테이퍼, 초기 비틀림각, 그리고 장착 각의 영향을 고려한 회전 블레이드의 진동해석 (Vibration analysis of rotating blades considering the cross section taper, the pre-twist angle, and the setting angle)

  • 이준희;유홍희
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2009년도 춘계학술대회 논문집
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    • pp.288-295
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    • 2009
  • Equations of chordwise and flapwise bending motions for the vibration analysis of rotating pre-twisted blades having tapered cross section and orientation angle are derived by using hybrid deformation variable modeling. The two motions are couples to each other due to the pre-twisted angle of the beam cross section. The derived equations are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters on the modal characteristics of rotating pre-twisted blades having tapered cross section and orientation angle are investigated. The eigenvalue loci veering phenomena is also investigated and discussed in this work.

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초기 비틀림각을 갖는 회전하는 다중 패킷 블레이드 시스템의 고유 진동 해석 (Modal Analysis of a Rotating Multi-Packet Pre-twisted Blade System)

  • 김민권;유홍희
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2008년도 춘계학술대회논문집
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    • pp.393-399
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    • 2008
  • A modeling method for the modal analysis of a pre-twisted multi-packet blade system undergoing rotational motion is presented in this paper. Blades are idealized as pre-twisted cantilever beams that are fixed to a rotating disc. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. The coupling effect between chordwise and flapwise bending deflection is also considered. Hybrid deformation variables are employed to derive the equations of motion. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters and the number of packets as well as blades on the modal characteristics of the rotating multi-packet pre-twisted blade system are investigated with some numerical examples.

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Vibration Analysis of Cantilever Plates Undergoing Translationally Accelerated Motion

  • Yoo, Hong-Hee;Kim, Sung-Kyun
    • Journal of Mechanical Science and Technology
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    • 제16권4호
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    • pp.448-453
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    • 2002
  • This paper presents a modeling method for the vibration analysis of translationally accelerated cantilever plates. An accurate dynamic modeling method, which was introduced in the previous study, is employed to obtain the equations of motion for the vibration analysis. Dimensionless parameters are identified to generalize the conclusions from numerical results. The effects of the dimensionless parameters on the natural frequencies and mode shapes are investigated. Particularly, the magnitude of critical acceleration which causes the dynamic buckling of the structure is calculated. Incidentally, the natural frequency loci veering phenomena are observed and discussed.

회전하는 테이퍼 단면 다중 패킷 블레이드 시스템의 진동 해석 (Vibration Analysis of a Rotating Multi-Packet Blade System Having Tapered Cross Section)

  • 김민권;유홍희
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회A
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    • pp.832-837
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    • 2008
  • A modeling method for the modal analysis of a multi-packet blade system having tapered cross section undergoing rotational motion is presented in this paper. Blades are idealized as tapered cantilever beams that are fixed to a rotating disc. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. Hybrid deformation variables are employed to derive the equations of motion. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters including tapered ratio and the number of packets as well as blades on the modal characteristics of the system are investigated with some numerical examples.

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가압기밀림관의 수평배관내 열성층유동 (Thermal stratification in a horizontal pipe of pressurizer surge line)

  • 정일석;김유;염학기;박만흥
    • 대한기계학회논문집B
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    • 제20권4호
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    • pp.1449-1457
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    • 1996
  • In this paper, the unsteady two dimensional model for the thermal stratification in the pressurizer surge line of PWR plant has been proposed to numerically investigate the heat transfer and flow characteristics. The dimensionless governing equations are solved by using the Control Volume Formulation and SIMPLE (Semi-Implicit Method for Pressure Linked Equations) algorithm. The temperature profile of fluids and pipe wall with time are shown when the thermal stratification occurs in the horizontal pipe. The numerical result shows that the maximum dimensionless temperature difference is about O.514 between hot and cold section of pipe wall at dimensionless time 1,632.