• Title, Summary, Keyword: 모형실험

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Variation of Flow conditions in T-type Cooling-Water-Pump Chambers with Increasing Inflows in Intake Canal (유량증가에 따른 T형 취수펌프장내의 흐름변화)

  • Yi, Yong-Kon;Cheong, Sang Hwa;Yoon, Byeong Mo;Kim, Chang Wan
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.1424-1428
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    • 2004
  • 본 연구는 유량증가에 따른 T형 취수펌프장내의 흐름상황변화를 수리 및 수치모형실험을 통하여 규명하였다. 수리모형은 1:20의 축척으로 제작되었고 수치모형은 RMA-2를 사용하였다. 수리모형실험은 취수펌프장내의 3차원 흐름현상을 살펴보기에 적절한 것으로 나타났다. 2차원 수치모형은 3차원 흐름현상을 토의하기에는 어려운 점이 있겠지만 경제적으로 여러 가지 상황에 대한 모형실험을 할 수 있는 장점을 이용하기 위하여 취수펌프장내 5D지점에서의 최대유속과 와도, 펌프 장내 최대유속, 냉각수취수로내의 최대유속을 2개의 취수로 공급유량에 대하여 비교하였다.

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River Hydraulic Analysis and Application Using EFDC Model Focused on Geumgang Weir Section (EFDC 모형을 이용한 금강보 구간 하천수리해석 및 적용성 검토)

  • Seo, Sung-Ho;Hur, Young-Teck;Jeong, Sang-Man
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.39-39
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    • 2011
  • 하천에서 수공구조물을 설계시 구조물의 규모, 형식, 운영방식, 안정성 등을 검토하기 위하여 일반적으로 수리모형실험과 수치모형실험을 이용한다. 수리모형실험은 자연현상의 왜곡을 최소화하여 검토결과를 얻을 수 있다는 장점이 있지만, 많은 시간과 비용, 인력 및 공간이 필요하기 때문에 단기간에 다양한 검토가 필요한 경우에는 많은 제약이 따른다. 반면에 수치모형실험은 제한적인 조건에서 검토목적 및 용도에 따라 다양한 수치모의기법을 활용하여 상대적으로 낮은 비용과 신속하고 다양한 검토가 가능하다는 장점을 가지고 있다. 그러나 수치모형실험은 어디까지나 자연현상에 대한 수학적, 물리적 기법을 활용한 분석이기 때문에 결과에 대한 신뢰성 확보가 매우 중요하다. 최근에는 컴퓨터의 계산능력 향상과 유체의 복잡한 동수역학적 거동 해석 기법의 다양화, 그리고 많은 적용성 검토 연구결과로 인한 신뢰성 향상 등으로 인해 수치모형실험에 대한 관심이 높아지고 있다. 본 연구는 현재 금강에 건설 중인 금강보에 대하여 다차원 수치모형인 EFDC(Environmental Fluid Dynamics Code)를 이용하여 하천 구조물 및 물리적 환경변화에 대한 정밀수리분석을 실시하기 위한 사전절차로, EFDC 모형을 하천수리해석에 적용할 경우 모형에 포함되어 있는 다양한 변수설정 및 제약조건들에 대하여 적용한계를 검토하고자 한다. 검토방법은 금강보가 건설되기 이전의 하천지형 상황에서 EFDC 모형과 HEC-RAS 모형을 이용한 수리분석을 수행하고, 수리거동 결과 들을 상호 비교 분석 한다. 수치모의 대상구간은 금강보 건설구간을 포함하여 약 20km 구간이고, 대상구간에 대하여 3차원 정밀지형자료를 구축하였으며, 과거 호우사상에 대한 구간 내 관측 수위 및 모형별 계산수위결과를 비교 검토하였다.

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Estimation of Hydraulic Effects Inside of Riverbank with Experimental Information Modeling (EIM을 이용한 제외지 수리모형 내 수리영향 분석)

  • Oh, Hee-Chang;Kim, Soo-Young;Joo, Sung-Sik;Lee, Seung-Oh
    • Proceedings of the Korea Water Resources Association Conference
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    • pp.147-147
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    • 2011
  • 이상기후 및 극한 홍수 발생빈도의 증가 등으로 인해 많은 수공 구조물이 붕괴 위험에 노출되어 있다. 사전 피해 예방 및 경감을 위해 다양한 수공구조물의 붕괴 현상에 대하여 수리실험적 접근방법을 통한 현상이해 및 예상결과 비교 검증이 필요하다. 그 중에서 제방붕괴에 대한 수리실험은 수치모의를 통한 분석의 어려움 때문에 대부분 모형실험을 통해서 이루어지고 있는 실정이다. 본 연구에서는 실제규모의 제방붕괴 선행실험의 측정결과를 활용하여 실험설계에 이용 하였다. 모형은 실험공간의 규모를 고려하여 축척을 1:10 으로하고, 하도내 흐름 안정을 위해 수로의 길이 는 16, 저폭은 $b\geq10h$를 만족하는 하천으로 설계하여 b를 3m로 설정 하였다. Fr수는 0.29로 원형과 동일하게 하고, 그에 따른 유량 ( )는 0.538m/s로 하였다. 실제 모형 제작에서는 현장 실험실의 펌프용량에 따른 가용유량 ($Q__{max}$)의 제약에 따라 수로가 직선이고 좌우가 대칭인 점을 감안하여 폭을 1/2로 절단 하고 유량은 $0.269m^3/s$(Q/2)를 공급하였다. 위와 같이 모형제작을 위한 실험 설계시 현장 여건을 고려하여 모형을 변형할 경우 EIM(Experimental Information Modeling)을 이용한 수리영향에 대한 분석을 통한 설계검증이 필요하다. FLOW-3D를 이용한 3차원 수치모의를 통하여 동일 지점에서의 유속과 수심을 분석하여 흐름양상을 비교 하였으며, 유속과 수심의 측정위치는 그림 1에 도시하였다. 수치모의 결과 측정지점에서의 수위가 하도 바닥을 기준으로 0.25m로 동일할 경우 수로 단면에 대한 유속 분포가 제방을 기준으로 2b/3까지는 유사한 경향을 보였다. 그 결과, $b\geq10h$인 수로에서 제방붕괴를 위한 모형 설계시 하도 폭을 1/2만 만들 경우에도 실험의 신뢰성이 확보된다는 것을 확인하였다.

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The Maximin Robust Design for the Uncertainty of Parameters of Michaelis-Menten Model (Michaelis-Menten 모형의 모수의 불확실성에 대한 Maximin 타입의 강건 실험)

  • Kim, Youngil;Jang, Dae-Heung;Yi, Seongbaek
    • The Korean Journal of Applied Statistics
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    • v.27 no.7
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    • pp.1269-1278
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    • 2014
  • Despite the D-optimality criterion becomes very popular in designing an experiment for nonlinear models because of theoretical foundations it provides, it is very critical that the criterion depends on the unknown parameters of the nonlinear model. But some nonlinear models turned out to be partially nonlinear in sense that the optimal design depends on the subset of parameters only. It was a strong belief that the maximin approach to find a robust design to protect against the uncertainty of parameters is not guaranteed to be successful in nonlinear models. But the maximin approach could be a success for the partial nonlinear model, because often the optimal design depends on only one unknown value of parameter, easier to handle than the full parameters. We deal with maximin approach for Michaelis-Menten model with respect to D- and $D_s$-optimality.

Comparison of Shallow Model Tunnel Test Using Image Processing and Numerical Analysis (이미지 프로세싱을 이용한 얕은 터널 모형실험과 수치해석의 비교)

  • Lee, Yong-Joo
    • Journal of the Korean Geotechnical Society
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    • v.22 no.7
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    • pp.5-12
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    • 2006
  • In this study, 2D shallow tunnel model test using close range photogrammetric technique was conducted with aluminium rods simulating continuum granular material. Numerical analysis was also carried out in order to identify the behaviour of subsurface deformations caused by shallow tunnelling. Direction and magnitude of displacement vectors from the model test were identical to the result of numerical analysis based on the model data. In particular, it is shown that the vector direction was toward a point below the tunnel invert level. A narrow "chimney or tulip like" pattern of vertical displacement was confirmed by both the model test and numerical analysis. This behaviour is consistent with the field data. In addition to the qualitative comparison, the quantitative result of subsurface settlements according to 2D volume loss showed good agreement between the model test and numerical analysis. Therefore, close range photogrammetric technique applied in the model test may be used to validate the result from the continuum numerical analysis.

Behavior Characteristics of Batter Piles by Model Test (모형실험에 의한 경사말뚝의 거동 특성)

  • 권오균;이활;석정우
    • Journal of the Korean Geotechnical Society
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    • v.20 no.8
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    • pp.59-66
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    • 2004
  • In this study, the behavior characteristics of vertical and batter piles were analyzed by the model tests and the numerical analyses. Model steel pipe piles with the inclination of 0$^{\circ}$, 10$^{\circ}$, 20$^{\circ}$ and 30$^{\circ}$ were driven into sands with the relative density of 79%. The static compression load tests and numerical analyses using PENTAGON 3D were performed. The bearing capacities of batter piles with inclination of 10$^{\circ}$, 20$^{\circ}$ and 30$^{\circ}$ were 111, 95, and 81% of those of vertical pile in model tests, and the results of numerical analyses were similar to those of model tests. The bearing capacities p.oposed by Petrasovits and Award (1968) were similar to those of model test in the inclination of 10$^{\circ}$, but overestimated in the inclination of 20$^{\circ}$ and 30$^{\circ}$. The skin frictions and end bearing loads were the maximum in the inclination of 10$^{\circ}$ and decreased with increasing the inclination angle.

Experimental Study on Hydraulic Characteristics and Vorticity Interactions of Floating Breakwaters (부유식방파제의 수리특성 및 와 상호작용에 관한 실험적 연구)

  • Yoon, Jae-Seon;Son, Hyok-Jun;Chun, Si-Young;Cho, Yong-Sik
    • Journal of Korean Society of Hazard Mitigation
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    • v.10 no.6
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    • pp.175-183
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    • 2010
  • In this study, laboratory experiments are conducted to investigate flow-fields around floating breakwaters by using the LDV(Laser Doppler Velocimetry) system. The LDV system is a well-known equipment to measure fluid particle velocities in laboratory experiments. Although the system requires great efforts and enormous time for measurements, it can provide precise velocity fields comparing to other available equipments. Various types of drafts and shapes for breakwaters are employed in laboratory experiments to analyze a relation between flow-fields and vorticity. A series of numerical experiments are also carried out by using a two-dimensional Navier-Stokes equations model. Numerically predicted results are compared with laboratory measurements.

Lateral Earth Pressures on Buried Pipes due to Lateral Flow of Soft Grounds (연약지반의 측방유동으로 인하여 매설관에 작용하는 측방토압)

  • Hong, Byungsik;Kim, Jaehong
    • Journal of the Korean Geoenvironmental Society
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    • v.11 no.9
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    • pp.27-38
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    • 2010
  • A series of model test as well as numerical analysis by FEM was performed to investigate lateral earth pressure acting on a buried pipe in soft ground undergoing horizontal soil movement. A model test apparatus was manufactured so as to simulate horizontal soil movement in model soft ground, in which a model rigid buried pipe was installed. The velocity of soil deformation could be controlled as wanted during testing. The model test was performed on buried pipes with various diameters and shapes to investigate major factors affected the lateral earth pressure. The result of model tests showed that the larger lateral earth pressure acted on the buried pipes under the faster velocity of soil movement. The result of numerical analysis, which was performed under immediate loading condition, showed a similar behavior with the result of model tests under 0.3mm/min to 1.0mm/min velocity of soil deformation. Most of model tests showed the soil deformation-lateral load behavior, in which the first yielding load developed at small soil deformation and elastic behavior was observed by the yielding load. Then, lateral load was kept constant by the second yielding load, in which plastic behavior was observed between the first yielding load and the second yielding one. Beyond the second yielding load, the compression behavior zone was observed. When the velocity was too fast, however, the lateral load was increased with soil deformation beyond the first yielding load without showing the second yielding load. The buried pipes with the larger diameter was subjected to the larger lateral load and the larger increasing rate of lateral load. At small soil deformation, the influence of diameter and shape of buried pipes on lateral load was small. However, when soil deformation was increased considerably, the influence became more and more.

A Note on Finding Optimum Conditions Using Mixture Experimental Data with Process Variables (공정변수를 갖는 혼합물 실험 자료를 활용한 최적조건 찾기에 관한 소고)

  • Lim, Yong B.
    • Journal of the Korean Society for Quality Management
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    • v.41 no.1
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    • pp.109-118
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    • 2013
  • Purpose: Given the several proper models for given mixture components-process variables experimental data, we propose a strategy to find the optimal condition in which the performance of the responses is well-behaved under those models. Methods: Given the mixture experimental data with process variables, first we choose the reasonable starting models among the class of admissible product models based on the model selection criteria and then, search for the candidate models that are the subset models of the starting model by the sequential variable selection method or all possible regressions procedure. Good candidate models are screened by the evaluation of model selection criteria and checking the residual plots for the validity of the model assumption. Results: We propose a strategy to find the optimal condition in which the performance of the responses is well-behaved under those good candidate models by adopting the optimization methods developed in multiple responses surface methodology. Conclusion: A strategy is proposed to find the optimal condition in which the performance of the responses is well-behaved under those proper combined models. This strategy to find the optimal condition is illustrated with the example in this paper.

Effect of Experimental Layout on Model Selection under Variance Components Models: A Simulation Study (분산성분모형에서 요인의 배치구조가 모형선택법에 미치는 영향에 대한 실험연구)

  • Lee, Yonghee
    • The Korean Journal of Applied Statistics
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    • v.28 no.5
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    • pp.1035-1046
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    • 2015
  • Variance components models incorporate various random factors in the form of linear models. There are two experimental Layouts for the classification of factors under variance components models: nested classification and crossed classification. We consider two-way variance components models and investigate the effect of experimental Layout on the performance of model selection criteria AIC and BIC. The effect of experimental Layout is studied through a simulation study with various combinations of parameters in a systematic fashion. The simulation study shows differences in performance of model selection methods between the two classification. There is a particular tendency to prefer the smaller model than the true model when the variance component of a nested factor becomes relatively larger than a nesting factor that is persistent even when the sample size is not small.