• Title/Summary/Keyword: fence

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Study of Wake Control by Blowing and Suction in Front of the Vertical Fence (수직벽 전방에서의 흡입/토출을 이용한 후류제어 연구)

  • Choi, Young-Ho;Kim, Hyoung-Bum
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.1
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    • pp.47-53
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    • 2008
  • The effect of periodic blowing and suction of upstream flow on the separated shear flow behind the vertical fence was experimentally investigated. The fence was submerged in the turbulent shear flow and DPIV method was used to measure the instantaneous velocity fields around the fence. Periodic blowing and suction flow was precisely generated by the syringe pump. Spanwise nozzle made 2D planar periodic jet flow in front of the fence and the effect of frequency and maximum jet velocity was studied. From the results, the reattachment length can be reduced by 60% of uncontrolled fence case under the control.

In Situ Rockfall Tests for Evaluation of Rockfall Protection Fences (국내 낙석방지울타리의 적정성 파악을 위한 현장 실물 실험 및 설계기준 제시)

  • 구호본;박혁진;이경미;김규한;이재욱
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.11a
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    • pp.629-634
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    • 2000
  • Rockfall protection fence which is used for mitigation of rockfall hazard, has been constructed without consideration of lithology, height and dip angle of rock slope. However, those factors should be considered for the construction of the protection fence. In addition, the protection fence should be evaluated its performance by in-situ test in order to utilize the fence effectively. This is the first full sized rockfall test in Korea. For this test, the rock cut slope whose height is about 20 m and dip angle is 65 $^{\circ}$ has been chosen. Based on the preliminary simulation procedure, four different concrete balls (0.5 ton, 1.0 ton, 2.0 ton and 5.0 ton) were prepared and four different types of protection fence were constructed. The results of this test will be utilized in the establishment of rockfall protection fence construction manual.

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Experimental Study of Manipulating the Vertical Fence Wake using the Vortex Generator (와류 생성기를 이용한 수직벽 후류 제어의 실험적 연구)

  • Lee, Sang-Hyuk;Kang, In-Su;Cha, Jae-Eun;Kim, Hyoung-Bum
    • Journal of the Korean Society of Visualization
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    • v.7 no.2
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    • pp.12-16
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    • 2010
  • The effect of vortex generators to manipulate the separated flow region behind the vertical fence was experimentally investigated. The experiments were performed in the circulating water channel. The parameters used in this study were the distance between the fence and vortex generators and size of vortex generators. Digital PIV method was applied to measure the instantaneous velocity fields around the fence. And the obtained flow properties were compared with those of fence How without the vortex generators. The obtained results quantitatively shows the specific size and distance of vortex generators which were effective to reduce the mean reattachment length of separation bubble behind the fence.

Application of Wingtip Fence on Smart Un-manned Aerial Vehicle(SUAV) (스마트 무인기에 Wingtip Fence 적용)

  • Chung, Jin-Deog;Choi, Sung-Wook;Cho, Tae-Whan
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.10
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    • pp.810-815
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    • 2008
  • To enhance aerodynamic efficiency of the Smart Un-manned Aerial Vehicle(SUAV) during the transition period, wingtip fence is attached at the end of wing. The application of wingtip fence is to reduce the effect of the separated flow caused by the nacelle on the wing especially when the tilting angle of nacelle is more than 30 degrees. To compare the effect of with and without wingtip fence, flow visualization and measurement of the aerodynamic coefficients using the pyramidal type external balance are done. Result of forces and moments measurement shows that the slope of lift coefficient is increased 18% and rolling moment of SUAV especially 60 & 90-degree tilting is changed in favorable manners with wingtip fence.

A study on the reduction in Ground Turbulence by the fence in the vicinity of airport runway (활주로 주변에 설치된 fence로 인한 Ground Turbulence의 감소 대한 연구)

  • Sheen, Dong-Jin;Hong, Gyo-Young;Kim, Young-In
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.17 no.4
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    • pp.32-41
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    • 2009
  • This paper presents the work being carried out in order to reduce the ground turbulence by the fence in the vicinity of airport runway. In preliminary study, we knows that cross-wind effect in the vicinity of runway is highly dependent on the shape of the buildings and have predicted results confirmed reduction of wind-effect by doing that set up the building with a fence, terraced shape or gap. This study is to figure out effect of ground turbulence by the building with fence, which is changing fence height, in using two-dimensional computational fluid dynamics analysis.

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Optimization Study of Pulsating Jet to Reduce the Separation Bubble behind the Fence (후방 박리기포 감소를 위한 맥동제트의 최적화 연구)

  • Choi, Young-Ho;Kang, In-Su;Kim, Hyoung-Bum
    • Journal of the Korean Society of Visualization
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    • v.6 no.1
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    • pp.53-58
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    • 2008
  • We carried out the experiments which controled the periodic jet in front of the fence to alter the fence wake. The experiments were performed in circulating water channel and the vertical fence was submerged in the boundary layer. The frequency, jet nozzle distance and speed of jet passing the slit were investigated. Each case divided into 20 phases and phase-averaged results were compared with uncontrolled fence flow. From the results, we found the specific frequency and nozzle distance which were good for reducing the reattachment length. In this case, the reattachment length was decreased 35% compared with the uncontrolled fence flow.

Experimental study of vertical fence wake with flow separator (Flow separator가 부착된 수직벽 후류유동의 실험적 연구)

  • Choi, Young-Ho;Kim, Hyoung-Bum
    • 한국가시화정보학회:학술대회논문집
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    • 2006.12a
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    • pp.68-72
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    • 2006
  • Vertical fence has the coherent flow structure in front of the fence. In the present study, the wake change due to the flow separator in front of the vertical fence was experimentally investigated. Quantitative method was applied to study the separated shear flow field. The results show the flow separator changes the downstream shear flow and alters the curvature of separated shear layer As the freestream velocity increased, the reattachment length also increased.

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Numerical investigations on the along-wind response of a vibrating fence under wind action

  • Fang, Fuh-Min;Ueng, Jin-Min;Chen, J.C.
    • Wind and Structures
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    • v.5 no.2_3_4
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    • pp.329-336
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    • 2002
  • The along-wind response of a surface-mounted elastic fence under the action of wind was investigated numerically. In the computations, two sets of equations, one for the simulation of the unsteady turbulent flow and the other for the calculation of the dynamic motion of the fence, were solved alternatively. The resulting time-series tip response of the fence as well as the flow fields were analyzed to examine the dynamic behaviors of the two. Results show that the flow is unsteady and is dominated by two frequencies: one relates to the shear layer vortices and the other one is subject to vortex shedding. The resulting unsteady wind load causes the fence to vibrate. The tip deflection of the fence is periodic and is symmetric to an equilibrium position, corresponding to the average load. Although the along-wind aerodynamic effect is not significant, the fluctuating quantities of the tip deflection, velocity and acceleration are enhanced as the fundamental frequency of the fence is near the vortex or shedding frequency of the flow due to the occurrence of resonance. In addition, when the fence is relatively soft, higher mode response can be excited, leading to significant increases of the variations of the tip velocity and acceleration.

Analysis on the Visual Preference and Image for the Fence (담장의 시각적 선호성 및 이미지 분석)

  • Jung, Sung-Gwan;Lee, Jeong
    • Journal of the Korean Institute of Landscape Architecture
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    • v.22 no.3
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    • pp.65-78
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    • 1994
  • This study deals with the consciousness and visual preference and image about the fence that is an important factor and a vertical element in the streetscape. The analysis was performed by the data obtained from the questionnaires and the photos for the fence scene. 1. The answerers considering the fence had great influence on the beauty of a city were over 80%, also the fence influence good effect on a city was higher than 63%. 2. The answerers prefering the fence materials mixed with inanimate materials and plants was higher than 50%. Also the design offence was regarded to be the most important element when established. 3. While the satisfying factors for the visual preference were peculiarity, abundance and harmony, the dissatisfying factors were commonplaceness, disharmony and isolation(closing). Also the preference factors were the design and material in several elements of the fence. 4. At the part of function, the preferable places were estimated highly as boundary mark, eye interception but in the visual effect were so low. 5. Psychological factor, related to the satisfaction of the fence, had a grip of three factors, evaluation, formation, potentiality, and the presumption formula was: Satisfaction=1.61(Evaluation)+0.30(Formation)+0.55(Potentiality)+6.23(R2=0. 63)

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The Characteristic of Wind Pressure of Low-rise Building Located Behind a Circle Wind Fence (원형방풍팬스 후면에 있는 저층건물의 풍압특성)

  • Jeon, Jong-Gil;You, Jang-Youl;You, Ki-Pyo;Kim, Young-Moon
    • Proceeding of KASS Symposium
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    • 2006.05a
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    • pp.102-109
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    • 2006
  • The effects of wind fence on the pressure characteristics around low-rise building model were investigated experimentally. Flow characteristics of turbulences behind wind fence were measured using hot-wire anemometer. The wind fence characterize by varying the porosity of 0 %, 40 % and the distances from the wind fence from 1 H to 6 H with maintaining the uniform flow velocity of 6 m/s. We investigated the overall characterization of the low-rise building by measuring pressure seventy four on model. The effects of porosity fences varied with the porosity of the fence and measurement locations(1H-6H). The 0% porosity proved to be effective for the protection area of 4H to 6H, but the 40% porosity proved to be effective for the protection area of 1H to 6H. The low-rise building of front face was found to be best wind fence for decreasing the mean, maximum and minimum pressure fluctuation.

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