• Title/Summary/Keyword: 연직도

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Comparison of an Analytic Solution of Wind-driven Current and all (x-$\sigma$) Numerical Model (취송류의 해석위와 (x-$\sigma$) 수치모형과의 비교)

  • 이종찬;최병호
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.4 no.4
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    • pp.208-218
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    • 1992
  • Analytic solutions for the gradient of surface elevation and vertical profiles of velocity driven by the wind stress in the one-dimensional rectangular basin were obtained under the assumption of steady-state. The approach treats the bottom frictional stress $\tau$$_{b}$ as known and includes vertically varying eddy viscosity $textsc{k}$$_{M}$, which is constant, linear and quadratic of water depth. When the $\tau$$_{b}$ is param-terized with surface stress, depth averaged velocity and bottom velocity, the result shows the relation of the no-slip bottom velocity condition and the bottom frictional stress $\tau$$_{b}$. The results of a mode splitted, (x-$\sigma$) coordinate, numerical model were compared with the derived analytic solutions. The comparison was made for the case such that $textsc{k}$$_{M}$ is the constant, linear and quadratic function of water depth. In the case of constant $textsc{k}$$_{M}$, the gradient of surface elevation and vertical profiles of velocity are discussed for a uniform depth, a mild slope and a relatively steep slope. When $textsc{k}$$_{M}$ is a linear and quadratic function of water depth, the vertical structures of velocities are discussed for various $\tau$$_{b}$. The result of the comparison shows that the vertical structure of velocities depends not only on the value of $textsc{k}$$_{M}$ but also on the profile of $textsc{k}$$_{M}$ and bottom stress $\tau$$_{b}$. Model results were in a good agreement with the analytic solutions considered in this study.his study.y.his study.

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Reproduction of Shallow Tides and Tidal Asymmetry by Using Finely Resolved Grid on the West Coast of Korea (서해연안 상세해상을 통한 천해조석 및 조석비대칭 재현)

  • Suh, Seung-Won
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.23 no.4
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    • pp.313-325
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    • 2011
  • Finite element grid system using h-refinement on the Yellow Sea was constructed based on previous study (Suh, 1999b) from 14 K to 210 K and special attention was concentrated on refining the coastal zone. In grid generation, depth change between adjacent points and non-dimensional tidal wave length ratio were considered. As a result approximately a quarter of the total nodes are located nearby 5 m of shallow area. Accurate bathymetry data using 30's and ETOPO1 with open boundary conditions of 8 major tidal constituents extracted automatically from FES2004 have been applied. In tidal simulation a 3-dimensional nonlinear harmonic model was setup and tidal amplification due to changes in vertical turbulent and bottom friction were simulated. In this study not only 8 major tidal constituents but also nonlinear shallow tides $M_4,$, $MS_4$ and long period $M_f,$, $M_{sf}$ were reproduced. It is found that implication of spatial variation of friction coefficient plays a very important role in reproduction of astronomical and shallow tides which are computed by iterative computation of nonlinear terms. Also it should be considered differently with respect to tidal periods. To understand the distribution of tidal asymmetry, amplitude ratio of $M_4/M_2$ and phase differences $2g(M_2)-g(M_4)$ were calculated. Tidal distortion ratio marks up to 0.2 on the west coast showing shallow coastal characteristics and somewhat wide range of ebb-dominances in front of Mokpo area are reproduced.

Efficient Floor Vibration Analysis in A Shear Wall Building Structure (벽식구조물의 효율적인 연직진동해석)

  • Kim, Hyun-Su;Lee, Dong-Guen
    • Journal of the Earthquake Engineering Society of Korea
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    • v.8 no.6 s.40
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    • pp.55-66
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    • 2004
  • Recently, many high-rise apartment buildings using the box system, composed of only reinforced concrete walls and slabs, have been constructed. In residential buildings such as apartments, vibrations occur from various sources and these vibrations transfer to neighboring residential units through walls and slabs. It is necessary to use a refined finite element model for an accurate vibration analysis of shear wall building structures. But it would take significant amount of computational time and memory if the entire building structure were subdivided into a finer mesh. Therefore, an efficient analytical method, which has only translational DOFs perpendicular to walls or slabs by the matrix condensation technique, is proposed in this study to obtain accurate results in significantly reduced computational time. If all of the DOFs except those perpendicular to walls or slabs in the shear wall structure eliminated using the matrix condensation technique at a time, the computational time for the matrix condensation would be significant. Thus, the modeling technique using super elements and substructuring technique is proposed to reduce the computational time for the matrix condensation. Dynamic analysis of 3-story and 5-story shear wall example structures were performed to verify the efficiency and accuracy of the proposed method. It was confirmed that the proposed method can provide the results with outstanding accuracy requiring significantly reduced computational time and memory.

Estimatation of Mean Velocity from Surface Velocity (표면유속을 이용한 평균유속 추정방법의 개발)

  • Roh, Young-Sin;Yoon, Byung-Man;Yu, Kwon-Kyu
    • Journal of Korea Water Resources Association
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    • v.38 no.11
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    • pp.917-925
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    • 2005
  • LSIV (Large Scale Image Velcocimetry) Is one of the image-based velocity measurement techniques. Since it measures surface velocities, it gives simple and inexpensive way to measure velocity, compared to other methods. Because of these advantages, there have been many studies to apply LSIV to the river discharge measurement in the field. Measuring the discharge by using LSIV requires a method which converts a surface velocity to a mean velocity In the present study, experiments and analysis of vortical velocity profile of open-channel flow in various conditions were performed to develop methods which estimate a mean velocity from a surface velocity. The result of this experiment reveals that velocity-dip phenomena occur at free-surface layer in open channel flow and Froude number affects more than bed roughness does. Two methods for estimating the mean velocity were proposed. One is to correct the wake law's profiles by using the difference of surface velocity from the mean velocity, and the other is to use the ratio of mean and surface velocities. The result of applying these methods in an experiment shows that they are quite accurate having an error of approximately $6\%$ only.

Optimization of Reinforcement Effect of Large-diameter Drilled Deep Foundation (보강형 현장타설말뚝의 최적보강효과 분석)

  • 남대승;김수일;이준환;윤경식
    • Journal of the Korean Geotechnical Society
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    • v.19 no.2
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    • pp.207-216
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    • 2003
  • Drilled deep foundations of large diameter are often used for foundations of transmission towers. As tower structures become larger in modern society, there is a need of more efficient and economical design of large-diameter drilled deep foundations. Reinforced drilled deep foundations are popular in Japan for the foundation of tower structures. Stiffeners attached to the shaft of the foundation are used to increase the shaft resistance. This study aims at analyzing the effect of reinforcement with large-diameter drilled deep foundations based on numerical analysis of the representative soil and rock conditions in Korea. The numerical analyses are conducted to analyze the reinforcement effect of various stiffener conditions of number, inclination, location and length. Regarding to number of stiffeners, the effect of reinforcement for weathered and soft rocks increases proportionally as the number of stiffeners increases. For weathered soil, however, the effect of reinforcement increases at a lower rate. The effect of stiffener location is nearly negligible for axially loading cases, while it is significant for laterally loading cases. For the laterally loading cases, upper locations of stiffener give greater reinforcement effect than that of lower location. For stiffener inclinations of axial loading cases, a stiffener inclination equal to 60$^{\circ}$ gives the greatest reinforcement effect.

Numerical Simulation of Local Circulation Over the Daechung Lake Area by Using the Mesoscale Model (중규모 수치 모델을 이용한 대청 호수 주변의 국지 순환 모의)

  • Byon, Jae-Young;Choi, Young-Jean;Seo, Beom-Keun
    • Journal of the Korean earth science society
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    • v.30 no.4
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    • pp.464-477
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    • 2009
  • In this study, we examined the patterns of local circulation over the Daechung lake area through the numerical experiment designed to investigate the impact of lake on the local circulation. The results of numerical experiment showed that the surface temperature predicted by WRF model was lower than the observation, while the wind speed was stronger than the observation. The local circulation over the lake area was characterized by a lake breeze induced by a horizontal thermal contrast between the lake surface and the Surrounding land. At Daecheong Lake, a lake breeze formed at 09 LST and dissipated at 18 LST, with maximum intensity at 15 LST. The vertical extent of the simulated circulation was about 1,200 m. The specific humidity increased as the humid air above the lake moved landward due to the daytime circulation of the lake breeze. The numerical experiments of sensitivity to existence of the lake showed that the simulated surface temperature decreased in the experiment with the lake. Wind speed was more intense around the lake area when the actual land use was substituted by grassland land use. The results of numerical experiments suggest that the lake-induced lake breeze circulation has an effect on the meteorology of planetary boundary layer around the lake.

Model Optimization for Sea Surface Wind Simulation of Strong Wind Cases (강풍 사례의 해상풍 모의를 위한 모형의 최적화)

  • Heo, Ki-Young;Lee, Jeong-Wook;Ha, Kyung-Ja;Jun, Ki-Cheon;Park, Kwang-Soon
    • Journal of the Korean earth science society
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    • v.29 no.3
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    • pp.263-279
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    • 2008
  • This study is concerned with the optimization of models using MM5 and WRF mesoscale numerical models to simulate strong sea surface winds, such as that of typhoon Shanshan on 17 September 2006, and the Siberian high event on 16 December 2006, which were selected for displaying the two highest mean wind speeds. The model optimizations for the lowest level altitude, physical parameters and horizontal resolution were all examined. The sea surface wind values obtained using a logarithmic function which takes into account low-level stability and surface roughness were more accurate than those obtained by adjusting the lowest-level of the model to 10 m linearly. To find the optimal parameters for simulating strong sea surface winds various physical parameters were combined and applied to the model. Model grid resolutions of 3-km produced better results than those of 9-km in terms of displaying accurately regions of strong wind, low pressure intensities and low pressure mesoscale structures.

An Experimental Study on the Evaluation of Smear Effect Considering In-situ Conditions (현장여건을 고려한 스미어 영향 평가에 관한 실험적 연구)

  • Park, Yeong-Mog
    • Journal of the Korean GEO-environmental Society
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    • v.13 no.8
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    • pp.85-94
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    • 2012
  • Evaluation of the smear effect caused by mandrel penetration into soft ground for a vertical drain installation is very important to predict the consolidation time of soft ground improvement. 30 kinds of laboratory model tests considering in situ conditions were conducted to investigate the formation of a smear zone and the decrease of coefficient of permeability in the disturbed zone. Three types(C(clay):M(silt)=1:1, 0.5:0.5, and 0:1) of reconstituted samples were used for 3 dimensional smear zone test. An experimental study was performed focusing on length of mandrel penetration, mandrel shape and size, earth pressure, and ground condition(unit weight and grain size distributions). Laboratory test results show that the length of mandrel penetration is the most critical factor for the formation of smear zone. As a result, the ratio between diameter of the smear zone($d_s$) and that of mandrel($d_m$) at field using long mandrel becomes larger than conventional $d_s/d_m$. The ratio between $d_s$ and $d_m$ ranges from 1.89 and 2.48 with the sample at C:M=1:0. It was also found that the $d_s/d_m$ value with the round shape of the mandrel is smaller than that of diamond one. The value of $d_s/d_m$ decreased with larger mandrel size, lower unit weight, and higher earth pressure. However, higher silt content led to increase of $d_s/d_m$. The ratio between coefficient of horizontal permeability in the smear zone($k_{hs}$) and that of undisturbed zone($k_{ho}$) ranged from 0.70 to 0.85. The test results imply that factors and values affecting $k_{hs}/k_{ho}$ show similar tendency with $d_s/d_m$.

Horizontal Behavior Characteristics of Umbrella-Type Micropile Applied in Sandy Soil Subjected to Seismic Motion (사질토 지반에 설치된 우산형 마이크로파일의 지진 시 수평거동 특성)

  • Kim, Soo-Bong;Son, Su Won;Kim, Jin Man
    • Journal of the Korean GEO-environmental Society
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    • v.21 no.7
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    • pp.5-16
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    • 2020
  • Currently, the seismic design standards have been strengthened due to the occurrence of the Gyeongju and Pohang earthquake, and seismic performance evaluation of existing facilities is being conducted. It aims to secure a seismic performance effect during earthquakes by improving the micro-pile method, which can be constructed in limited confined places while minimizing damage to existing facilities. The improvement method is to construct all the piles in the square-tray-type plate on the top of the pile by constructing the slope pile in the form of an umbrella around the vertical pile, the main pillar. In this paper, the numerical analysis was performed to analyze the horizontal displacement behavior of an umbrella-type micropile for various real-measurement seismic waves in sandy soil. As a result of numerical analysis, the softer the ground, the better the effect of horizontal resistance of umbrella-type micropile. The horizontal displacement reduction effect was pronounced when the embedded depth was 15 m or more at the same ground strength, and it was found to be effective in earthquakes if it was settled on the ground with an N value of 30 or more. The embedded depth and horizontal displacement suppression effect of the micropile was proportional. Generally, the weaker the ground, the greater the displacement suppression effect. Umbrella-type micropile had a composite resistance effect in which the vertical pile resists the moment and inclined pile resists the axial force.

The Effect of indoor illuminance depends on direction of the side windows lighting (측창채광의 방향에 따른 실내조도의 영향)

  • Cho, Shee-Man;Kim, Won-Joong;Jang, Woo-Jin
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2004.05a
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    • pp.253-260
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    • 2004
  • 실내의 조명은 자연채광방식과 인공조명으로 나누어지는데 자연형 채광방식에서도 측창채광과 천창채광, 정 측창채광 그리고 반사 채광방식이 있다. 측창채광은 벽면에 대하여 일반적으로 연직인 창에 의한 채광을 말한다. 측창채광의 방향에 따라 실내조도는 영향을 많이 받는다. 따라서 본 연구는 측창채광의 동서남북의 방향에 따라 봄, 여름, 가을, 겨울의 계절에 따라 아침, 점심, 저녁시간대에 따라 변화되는 실내조도를 알아보았다. 실험방법은, 조명시뮬레이션 프로그램인 Lightscape V3.2를 사용하여 교실공간의 치수와 작업면의 높이를 가로 5.8[m], 세로 10.8[m], 높이 3[m], 작업면의 높이 0.75[m]로 정하였고, 각 시설물의 반사율[p]은 벽 80%, 창문 12%, 출입문 13%, 바닥 20%, 천장 85%로 지정하였으며 창문의 투과율은 88%로 설정하였다. 본 연구에서 측정하고자 하는 변수 값은 계절은 여름을 6월20일, 겨울은 1월20일 기준으로 하고 시간대는 09시, 13시, 18시로 하였으며 창측방위는 동, 서, 남, 북으로 정하였으며 계절과 시간은 가장 차이가 많이 나는 값을 선택하였다. 결론으로 창이 남쪽일 때 평균조도가 9,100[lx]로 가장 높았고, 시간별로는 점심에 19,590[lx]로 조도가 가장 높은 것을 알 수 있었고 조도 균제도는 창이 동쪽일 때 겨울에 가장 높았다. 창이 북쪽일 때는 여름이 겨울보다 평균조도가 약간 높았고, 시간별로는 아침에 조도가 약간 높은 것을 알 수 있었고 전체적으로 북쪽 창에서 실내조도가 현저하게 떨어지는 것을 알 수 있었다. 이와 같은 결과로 측창의 브라인드를 현재 사용하고 있는 수직 브라인드 대신에 수평 브라인드를 사용하여 주광의 범위를 넓게 조절하여 사용하게 하고, 점등제어를 현재 측창면과 수직으로 되어있는 배열을 수평으로 한다면 자연채광의 효과를 배가 할 수 있으리라고 사료된다. 미백 전, 미백후, 재광화 후 미세경도 변화 양상이 미백을 하지 않은 대조군과 차이를 보이지 않았으며 (p > 0.05) 미백 전과 미백 후의 미세경도의 차이 미백후와 재광화 후의 미세경도의 차이도 유의할 만한 차이가 없었다 (p > 0.05). 따라서 시중에 판매되고 있는 whitening strip과 미백 젤은 14일 동안의 통상적인 미백과정 동안 법랑질의 미세경도에 영향을 미치지 않는 것으로 사료된다.able pitch와 helical angle보다는 근본적으로 radial land가 screw-in effect의 예방에 더 큰 역할을 하는 것으로 추정될 수 있다 따라서 NiTi file의 사용 경험이 없는 초심자의 경우 근단부 폭경의 유지능력이 좋은 ProFile$^{(R)}$의 사용이 추천된다.)되었다.였으나 강남콩군 외에는 단백질의 소화 흡수율 및 효율은 크게 향상되지 않아 단백질의 소화 흡수율을 떨어뜨리는 요인에 관한 연구가 집중적 으로 이루어져야 하리라고 생각된다.면 바로 위 지점의 풍속을 측정하였다. 각 Seeding 물질에 대해 팬을 켜지 않았을 때, 즉 바람의 영향이 없을 때 측정한 표면유속을 바람의 세기가 변한 경우의 기준 표면유속으로 이용하였다. 본 연구의 결과 비중이 0.01 내외인 Ecofoam과 white polystyrene에 비해 비중이 0.92인 black polypropylene은 대부분이 물속에 잠겨 있어 흐름과 거의 일치하여 움직임을 알 수 있었다. 또한 흐름의 평균유속이 0.165 m/s의 저유속에서 바람이 tracers에 미치는 영향이 평균유속 0.558m/s인 경우보다 커서, 바람의 세기의 증가에 따라 표면유속 측정값이 급속히 감소되었다. 흐름의 평균유속이 큰 경우에는 바람이 tracer에 마치는 영향이 현격히 줄어듬을 보이고 있다. 결론적으로 유속이 증가함에 따라 바람의 영향은 감소하나, 바

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