• Title/Summary/Keyword: Aspect Ratio

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Effect of the Swirler Angle and Aspect Ratio of Nozzle on the Mean Velocity and SMD of Twin Sprays (노즐의 스월러각과 형상비가 이중분무의 평균속도와 입경의 크기에 미치는 영향)

  • Kim, Young-Jin;Jung, Ji-Won;Choi, Gyoung-Min;Kim, Duck-Jool
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.28 no.11
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    • pp.1459-1466
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    • 2004
  • The purpose of this study is to investigate the effect of swirler angle and the aspect ratio of swirl chamber of nozzle on the characteristics of single and twin spray. The characteristics of sprays have been investigated by measuring the spray angle, droplet size and velocity. Visualization of spray was conducted to obtain the spray angle and breakup process. The spray characteristics such as droplet size and velocity were measured by Phase Doppler Anemometry(PDA). It was found that the spray angle was increased with increasing the swirler angle. For both sprays, the axial velocity and SMD were decreased with increasing the swirler angle. It was also shown that the axial velocity and SMD were decreased with increasing the aspect ratio of swirl chamber, but for the twin spray, the axial velocity and SMD were not influenced significantly by the changing the aspect ratio of swirl chamber. The effect of swirler angle on the spray characteristics was greater than the aspect ratio of swirl chamber for single spray. The nozzle pitch was one of the important factors affecting the spray characteristics of twin spray.

Effect of Aspect Ratio on Direct Tensile Response of Strain Hardening Cement Composites with PET and PVA Fiber (PET 및 PVA섬유를 사용한 변형경화형 시멘트 복합체의 직접인장거동에서 섬유 형상비의 영향)

  • Jeon, Esther;Yun, Hyun-Do;Park, Wan-Shin;Kim, Yong-Chul;Kim, Yun-Su
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.913-916
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    • 2008
  • Direct tensile response of strain hardening cement composites(SHCC) depends primarily on the material's tensile response, which is a water cement ratio, direct function of fiber and matrix characteristics, the bond between them, and the fiber volume fraction. This paper discusses effect of aspect ratio of the direct tensile response of SHCC with PET and PVA fibers. The main variables considered include the aspect ratio of PET fibers(Aspect ratio, ${\ell}/d_f$ : 150, 300, 600). For the same mixture proportion, PET1.5+PVA0.5-300 and PET1.5+PVA 0.5-600(Aspect ratio 300, 600) showed better overall behavior(Pseudo strain-hardening, Multiple cracking) than specimens with PET1.5+PVA0.5-150(Aspect ratio 150). Tensile strain of PET1.5+PVA0.5-300 and PET1.5+PVA 0.5-600 at ultimate tensile stress were 0.5, 2.0% respectively.

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Optimization Design of Compact Diffuser (소형 디퓨저의 최적화 설계)

  • Lee, Young Tae
    • Journal of the Semiconductor & Display Technology
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    • v.21 no.4
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    • pp.163-167
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    • 2022
  • In this paper, an optimization design method of a diffuser using Bernoulli's theorem was reviewed. The aspect ratio of the cylindrical diffuser chamber and the diameter ratio of the air inlet and outlet were used as design parameters. For the optimal design of the cylindrical diffuser chamber, the air flow inside the chamber was simulated using ANSYS while changing the aspect ratio of the chamber. In order to confirm the simulation results, the diffuser manufactured using the laser processing machine was measured. Through ANSYS simulation and measurement, it was found that the optimal design condition was when the aspect ratio (chamber height/radius) of the diffuser chamber was 1/2 and the diameter ratio of the air inlet and outlet was also 1/2.

A Study on Vortex Shedding Characteristics of Rectangular Marine Structure With Aspect Ratio (장방형 해양구조물의 변장비에 따른 와방출 특성에 관한 연구)

  • 김진구;조대환
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.5 no.2
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    • pp.35-44
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    • 1999
  • High negative pressure coefficient is formed in the corner of the bluff body structures. For many curtain wall designers this phenomena is of interest because this high negative pressure coefficient is adopted in structural calculation. The present study is aimed to investigate shedding vortex characteristics of two-dimensional rectangular prism flow. Unsteady calculation by finite difference method based upon SOLA is carried out for three aspect ratios(1:1, 1:2, 1:3) of Re=10$^4$ in viscous incompressible flow within infinite domain. Fluctuation of velocity components at various pick-up points and time variation of drag and lift coefficients are analysed by FFT method to reveal shedding vortex frequency patterns. At aspect ratio 1:1, one primary Strouhal number appears for about all pick-up points. At aspect ratio 1:2, two representative Strouhal numbers are classified by pick-up positions and their flows show two different reattachment patterns. For aspect ratio 1:3, frequency spectrum maintains multiple peaks.

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Quasi Static Test of Real Scaled RC Piers with Low-Aspect Ratio (저형상비 RC교각의 실물모형 준정적실험)

  • Cho, Chang-Beck;Kwahk, Im-Jong;Kim, Young-Jin
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05a
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    • pp.218-221
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    • 2006
  • The past Korean Bridge Design Specifications have no limitation on the amount of lap splices of longitudinal bars in the plastic hinge zone of piers. A majority of bridge piers which have been non-seismically designed might have some lap splices in plastic hinge zone. Also a number of those piers in Korea have a low aspect ratio(height/section area). So, some problems such as low ductility behavior may happen. In this study, the real pier which was non-seismically designed and has a low aspect ratio was selected for the quasi-static tests. Two groups of full scaled RC pier models of which aspect ratios are about 2.26 and about 2.67 were fabricated. And then, quasi-static tests according to the drift level history method were implemented. From the test results, the failure of these test specimens have been shown in the complex shear-flexural or shear modes. The low aspect ratio and the lap splice have largely influenced on the seismic performance of bridge piers.

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Resonance Frequency of the Natural Convection in the Closure Cavity for the Variable Aspect Ratio (종횡비가 변하는 공동 내 자연대류의 공진주파수)

  • Chun, Kun-Ho;Joo, Kwang-Sup;Choi, Young-Don
    • Proceedings of the KSME Conference
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    • 2000.11b
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    • pp.609-614
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    • 2000
  • This numerical study investigate resonance frequency of natural convection for steady state, periodic flow and chaotic flow in two-dimensional direct numerical simulations, differentially heated, vertical cavities having aspect ratios near unity. The enclosure cavity has isothermal and time dependent temperature side walls and adiabatic top/bottom walls. The aspect ratio is 1/3, 1/2, 1, 2, and 3 for the varying Rayleigh number. Resonance frequency for AR=1 has decrease as the aspect ratio and the Rayleigh number are increasing.

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Effect of Aspect Ratio on Gas Microchannel Flow (마이크로채널 흐름에 관한 종횡비의 영향)

  • Tajul, Islam;Lee, Y.W.
    • Journal of Power System Engineering
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    • v.11 no.3
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    • pp.16-21
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    • 2007
  • Three dimensional numerical study was carried out to investigate the effect of aspect ratio on microchannel flow. We considered five straight rectangular channels with aspect ratios (height/width) 0.2, 0.4, 0.6, 0.8 and 1.0. Nitrogen gas flow was investigated for both slip and noslip wall boundary conditions. Isothermal wall condition was assumed. We used control volume method for this simulation. The slip velocity increases with the increase of aspect ratio. Friction coefficient decreases with the increase of aspect ratio. Slip friction coefficient is lower than noslip friction coefficient. Mass flow rate of slip model is higher than that of noslip model. We compared our results with the experimental result reported in the literature. The agreement was good.

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The Effect of the Aspect Ratio on the Natural Frequency of the Advanced Composite Structures (복합신소재 구조물의 형상비에 따른 고유진동수의 영향)

  • Kim, Yun Young;Han, Bong Koo
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.5 no.4
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    • pp.18-23
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    • 2014
  • In this paper. the effects of the aspect ratio on the natural frequency of the advanced composite road structures is studied. The advanced composite structures are too difficult for such design engineers for construction and some simple but accurate enough methods are necessary. Some laminate orientations have decreasing values of $D_{16}$, $B_{16}$, $D_{26}$ and $B_{26}$ stiffnesses as the ply number increases. The plate aspect ratio considered is from 1 to 5. Most of the road structures have large aspect ratios, for such cases further simplification is possible by neglecting the effect of the longitudinal moment terms.

Process Map for Improving the Dimensional Accuracy in the Multi-Stage Drawing Process of Rectangular Bar with Various Aspect Ratio (다양한 종횡비의 직사각바 다단 인발공정에서 치수정도 향상을 위한 프로세스 맵)

  • Ko, P.S.;Kim, J.H.;Kim, B.M.
    • Transactions of Materials Processing
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    • v.27 no.3
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    • pp.154-159
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    • 2018
  • In the rectangular bar multi-stage drawing process, the cross-section dimensional accuracy of the rectangular bar varies depending on the aspect ratio and process conditions. It is very important to predict the dimensional error of the cross-section occurring in the multi-stage drawing process according to the aspect ratio of the rectangular bar and the half die angle of each pass. In this study, a process map for improving the dimensional accuracy according to the aspect ratio was derived in the drawing process of a rectangular bar. FE-simulation of the multi-stage shape drawing process was carried out with four types of rectangular bar. The results of the FE-simulation were trained to the nonlinear relationship between the shape parameters using an Artificial Neural Network (ANN), and the process maps were derived from them. The optimum half die angles were determined from the process maps on the dimensional accuracy. The validity of the suggested process map for aspect ratios 1.25~2:1 were verified through FE-simulation and experimentation.

Numerical Analysis for the Air-Side Convective Heat Transfer Characteristics in a Compact Heat Exchanger with Flat Tubes and Plate Fins According to the Aspect Ratio (종횡비에 따른 납작관-평판휜 형상의 밀집형 열교환기 내공기 측 대류열전달특성에 대한 수치해석)

  • Moh, Jeong-Hah
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.9
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    • pp.695-703
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    • 2008
  • Numerical analysis has been carried out to investigate air-side convective heat transfer characteristics in a compact heat exchanger with flat tubes and continuous plate fins according to the aspect ratio. RNG k-$\varepsilon$ model is applied for turbulence analysis. Simulation results such as air velocity and temperature distributions are presented, and heat transfer coefficients are compared with previous correlations for circular tubes. The numerical conditions are considered for the aspect ratios ranging from 3.06 to 5.44 and Reynolds number ranging from 1000 to 10,000. The results showed that heat transfer coefficients decreased with the increase of aspect ratio. From the calculated results a correlation of Colburn j factor for the considered aspect ratio in the compact heat exchanger system is suggested. The predicted results in this study can be applied to the optimal design of air conditioning system.