• Title/Summary/Keyword: momentum transfer

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Mass and Heat Transfer Characteristics of Vertical Flat Plate with Free Convection

  • Kim Myoung- Jun
    • Journal of Advanced Marine Engineering and Technology
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    • v.29 no.7
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    • pp.729-735
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    • 2005
  • This paper has dealt with the characteristics of mass and heat transfer of vertical flat plate with free convection. The theory of similarity transformations applied to the momentum and energy equations for free convection. To derive the similarity equation of mass transfer. the equation for conservation of species was added to the continuity. momentum and energy equations. The momentum, energy and species equations set numerically to obtain the velocity, temperature and mass fraction of species as dimensionless. For cases where momentum transport dominates, the thermal boundary layers are shorter than the momentum boundary layer. The relationships between momentum, energy and species were clarified from this study.

The Analysis of the transfer of angular momentum on upper extremity during free Throw Motion in Basketball (농구 자유투 동작시 상지분절의 각운동량 전이 분석)

  • Yang, Dong-Young
    • Korean Journal of Applied Biomechanics
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    • v.13 no.1
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    • pp.185-204
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    • 2003
  • The purpose of this study was to obtain the data for stable and accurate techniques of the free throw in basketball. The subjects of this study were seven male basketball player consisted of college students athletes. Free throw motions were taken by video camera. The three-dimensional coordinates was processed by DLT. The variables were the velocity, the angular velocity of the upper extremity segments, degree, and angular momentum. The result of analysis is summarized as follows. 1. The velocity and angular velocity of the upper extremity segment was showed an gradual increase and a smooth velocity transfer, transferring from proximal segment to distal segment at free throw motion in basketball. 2. The local term and remote term angular velocity momentum of the proximal segment showed larger than that of the distal segment in X, Y, Z axis component all. 3. The remote term angular momentum was showed larger than that of the local term angular momentum in X, Y, Z axis component all. 4. The angular motion of the upper trunk and upper arm, upper arm and forearm was showed in opposite direction and symmetrical angular momentum in local term angular momentum of the Y and Z axis component. 5. All the segments of upper extremity segment was showed left rotation in remote term angular momentum of the Y axis component and right rotation in remote term angular momentum of the Z axis component.

Heat Transfer on Secondary Injection Surface in Supersonic Flow-field with Various Injection Angle (초음속 유동장내 2차분사 분사각도 변화에 따른 열전달 특성 변화)

  • Song, Ji-Woon;Yi, Jong-Ju;Cho, Hyung-Hee;Bae, Ju-Chan
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.11a
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    • pp.321-325
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    • 2008
  • In this paper, heat transfer changes due to the shock/boundary layer interaction were investigated on surfaces where secondary jet are injected. With an infra-red thermography, surface temperature was measured and the measured data was used to obtain the convective heat transfer. Heat transfer is enhanced with increment of momentum ratio. And normal injection case has a higher heat transfer value than that of 15 degrees inclined injection case. Secondary injection momentum ratio and injection angle affect the surface heat transfer distribution.

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Analysis of Globular Transfer Considering Momentum Induced by Flow Within Molten Drop in GMAW (용적 내부의 유동에 의한 모멘텀을 고려한 GMA 용접의 입상용적 이행에 대한 해석)

  • Arif, Nabeel;Lee, Seung-H.;Kang, Moon-J.;Yoo, Choong-D.
    • Journal of Welding and Joining
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    • v.26 no.4
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    • pp.61-65
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    • 2008
  • The static force balance model (SFBM) has been used to analyze drop transfer in gas metal arc welding. Although the SFBM is capable of predicting the detaching drop size in the globular mode with reasonable accuracy, discrepancy between the calculated and experimental results increases with current. In order to reduce discrepancy, the SFBM is modified by considering the momentum of the molten metal flow, which is generated by the pinch pressure. The momentum increases with smaller drop size and becomes compatible to the electromagnetic force. The modified force balance model (MFBM) predicts the experimental results more accurately, and extends its application to the projected mode.

Heat Transfer Coefficient and Shear Factor Subjected to Both Oscillating Flow and Oscillating Pressure in Pulse Tubes (주기적인 유동과 압력의 변화를 수반하는 맥동관의 열전달계수와 전단계수)

  • Jeong, Eun-Soo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.3
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    • pp.220-227
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    • 2007
  • Heat transfer and momentum transfer under conditions of both oscillating flow and oscillating pressure within pulse tubes show very different behavior from those for steady state conditions. The analytic solutions of axial velocity and temperature of the gas within pulse tubes were obtained by assuming that the variations in pressure and temperature were purely sinusoidal and small. The shear stress and the heat flux at the tube wall obtained from the solutions are expressed in terms of the cross-sectional averaged velocity, the difference between mean temperature and instantaneous cross-sectional averaged temperature and the difference between mean pressure and instantaneous pressure. It is shown that the complex shear factor, which has been applied to momentum transfer of incompressible oscillating flow, and the complex Nusselt number, which has been applied to either heat transfer with oscillating pressure only or heat transfer of incompressible oscillating flow, could also be used for momentum transfer and heat transfer subjected to both oscillating flow and oscillating pressure, respectively.

Effects of radiation-modulated cooling on the momentum transfer from stellar feedback

  • Na, Chongsam;Kimm, Taysun
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.70.2-70.2
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    • 2019
  • Strong radiation fields can change the ionization state of metals and hence cooling rates. In order to understand their effects on the momentum transfer from radiation and supernova feedback, we perform a suite of radiation-hydrodynamic simulations with radiation-modulated metal cooling. For this purpose, we pre-tabulate the metal cooling rates for a variety of spectral shapes and flux levels with the spectral synthesis code, Cloudy, and accurately determine the rates based on the local radiation field strength. We find that the inclusion of the radiation-modulated metal cooling decreases the total radial momentum produced by photo-ionization heating by a factor of ~3 due to enhanced cooling at temperature T~10^3-4 K. The amount of momentum transferred from the subsequent SN explosions, however, turns out to be little affected by radiation, as the main cooling agents at T~10^5-6 K are only destroyed by soft X-ray radiation which is generally weak. We further discuss the total momentum budget in various conditions.

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Estimation of Atmospheric Turbulent Fluxes by the Bulk Transfer Method over Various Surface (다양한 지표면 위에서 총체 전달 방법에 의한 대기 난류 플럭스 추정)

  • Kim, Min-Seong;Kwon, Byung-Hyuk;Kang, Dong-Hwan
    • Journal of Environmental Science International
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    • v.23 no.6
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    • pp.1199-1211
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    • 2014
  • The momentum flux and the sensible heat flux were measured with the scintillometers and ultrasonic anemometers at 6 sites of which surface characteristics like roughness length and zero-displacement are different each other. We estimated the momentum flux and the sensible heat flux based on the bulk transfer method with the drag coefficient and the heat transfer coefficient calculated from the temperature and wind speed at two heights. The variation of bulk transfer coefficients showed a remarkable difference depending on the atmospheric stability which is less influenced by the zero-displacement than the roughness length. The estimated sensible heat fluxes were in good agreement with those measured at 3 m, showing 23.7 $Wm^{-2}$ of the root mean square error that is less than 10% of its maximum. Since the estimated momentum flux is not only effected by drag coefficient but also by wind speed square, the determination of wind speed in the bulk transfer method is critical.

A Naphthalene Sublimation Study on Heat/Mass Transfer for Flow over a Flat Plate

  • Park, Jong-Hark;Yoo, Seong-Yeon
    • Journal of Mechanical Science and Technology
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    • v.18 no.7
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    • pp.1258-1266
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    • 2004
  • It is important to completely understand heat/mass transfer from a flat plate because it is a basic element of heat/mass transfer. In the present study, local heat/mass transfer coefficient is obtained for two flow conditions to investigate the effect of boundary layer using the naphthalene sublimation technique. Obtained local heat/mass transfer coefficient is converted to dimensionless parameters such as Sherwood number, Stanton number and Colburn j-factor. These also are compared with correlations of laminar and turbulent heat/mass transfer from a flat plate. According to experimental results, local Sherwood number and local Stanton number are in much better agreement with the correlation of turbulent region rather than laminar region, which means analogy between heat/mass transfer and momentum transfer is more suitable for turbulent boundary layer. But average Sherwood number and average Colburn j-factor representing analogy between heat/mass transfer and momentum transfer are consistent with the correlation of laminar boundary layer as well as turbulent boundary layer.

Turbulent Flow and Heat Transfer in an Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류운동과 열전달)

  • 안수환;이윤표
    • Transactions of the Korean Society of Automotive Engineers
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    • v.4 no.5
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    • pp.26-36
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    • 1996
  • The fully developed turbulent momentum and heat transfer induced by the square-ribbed roughness elements on both the inner and outer wall surfaces in concentric annuli are studied analytically based on a modified turbulence model. The analytical results of the fuid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity positions and friction factors, and etc. shown in Fig.1. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Reynolds number, Nusselt bumber and Prand시 number. The study demonstrates that certain artificial roughness elements may be used to enhance heat transfer rates with advantage from the overall efficiency point of view by investigating turbulent flows and heat transfer in Fig.1.

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Turbulent Flow and heat Transfer in the Annular Passage with Repeated-Ribbed Roughness on Both Walls (양측벽면에 반복돌출형 거칠기가 있는 이중관통로내의 난류유동과 열전달)

  • 안수환;김덕현
    • Journal of Advanced Marine Engineering and Technology
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    • v.20 no.1
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    • pp.1-12
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    • 1996
  • The fully developed tubulent momentum and heat transfer induced by the square- ribbed roughness elements on both the inner and outer wall surfaces in the concentric annuli are studied analytically based on a modified turbulence model. Heat transfer coefficients for two conditions, i.e, a) inner wall heated as constant heat flux and outer wall insulated b) inner wall insulated and outer wall heated as constant heat flux, are investigated. The analytical results of the fluid flow are verified by experiment. The experiment is done with a pitot tube and a X-type hot wire anemometer to measure the time mean velocity profiles, zero shear stress positions, maximum velocity profiles and friction factors, and etc. The resulting momentum and heat transfer are discussed in terms of various parameters, such as the radius ratio, the relative roughness, the roughness density, Nusselt number and Prandtl number.

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