• Wind and Structures
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• 제37권6호
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• pp.461-471
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• 2023

The main objective of this study was to establish design guidelines for three key design variables (spar thickness, spar diameter, and total draft) by examining their impact on the stress distribution and resonant frequency of a 2.5-MW spar-type floating offshore wind turbine substructure under extreme marine conditions, such as during Typhoon Bolaven. The current findings revealed that the substructure experienced maximum stress at wave frequencies of either 0.199 Hz or 0.294 Hz, consistent with previously reported experimental findings. These results indicated that the novel simulation method proposed in this study, which simultaneously combines hydrodynamic diffraction analysis, computational dynamics analysis, and structural analysis, was successfully validated. It also demonstrated that our proposed simulation method precisely quantified the stress distribution of the substructure. The novel findings, which reveal that the maximum stress of the substructure increases with an increase in total draft and a decrease in spar thickness and spar diameter, offer valuable insights for optimizing the design of spar-type floating offshore wind turbine substructures operating in various harsh marine environments.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.361-366
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• 2001

The present study describes a practical estimation procedure about the pantograph under several severe aerodynamic load conditions. As the operating speed of the Korean Train Express(KTX) reaches 350km/h, structural safety at various conditions should be examined at the design stage. In the present study, a compact and reliable procedure is developed to get aerodynamic loads on each part of the pantograph regarding the typhoon condition, the train/tunnel interaction, the train/train interaction and the side wind condition. In the estimation procedure, 3-dimensional steady and unsteady CFD simulation around the high speed train facilitates assigning the external local flow condition around the pantograph. The procedure is verified using the results of the low speed wind tunnel test at JARI and applied to 7 flow conditions and 4 operation configurations.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1945-1949
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• 2006

A storm-induced coastal inundation model (SICIM) is presented to simulate the flood event during typhoon passage that often results in significant rise in sea-level heights especially in the upstream region of the basin. The SICIM is a GIS-based distributed hydrodynamic model, both storm surge and storm water inundations are taken into account. The spatial and temporal distribution of the storm water level and flux are calculated. The model was applied to Jeju Island since it has an isolated watershed that is easy to handle as a first step of model application. Another reason is that it is surrounded by coastal area exposed to storm surge inundation. The model is still advancing and will be the framework of a predictive early inundation warning system.

• Wind and Structures
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• 제24권6호
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• pp.637-656
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• 2017

In Japan, at least 28 local winds are known by name, most of them associated with downslope windstorms and gap winds. To review these windstorms, we categorize them based largely on the atmospheric conditions and formation mechanisms, and then focus on representative examples. These representative cases include the "Yamaji­kaze", a typical downslope windstorm, the "Hirodo-­kaze", a downslope windstorm induced by a nearby typhoon (intense tropical cyclone), and the "Karak-kaze", a downslope wind with a clear diurnal variation. Other downslope winds such as the "Inami-kaze" and the gap wind "Kiyokawa­dashi" are also described. Among these winds, the "Yamaji-kaze", "Hirodo-kaze", and "Kiyokawa-dashi" are considered the three most notorious due to their destructive power. After describing and comparing these winds, we discuss remaining issues to be considered in future studies.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.241-241
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• 2015

In this study, the simulations and analyses of flood flow due to a river inundation in a coastal urban area are carried out using a two-dimensional finite volume method with well-balanced HLLC scheme. The target area is a coastal urban area around Gohyun river which is located at Geoje city in Kyungnam province in Korea and was extremely damaged due to the heavy rainfall during the period of the typhoon "Maemi" in September 2003. For the purpose of the verification of the numerical model applied in this study, the simulated results are compared and analyzed with the inundation traces. Moreover, the flood flow in a urban area is simulated and analyzed based on the scenarios of inflow to the river with the increase and decrease of the intensity of the heavy rainfall.

• Wind and Structures
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• 제1권1호
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• pp.67-75
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• 1998

Tiger Gate Bridge, a steel suspension bridge with a main span of 888 m and a stiffening box girder, is located at the Pearl River Estuary, Guangdong Province, one of the typhoon-prone area in China. Focusing on the developing of the full aeroelastic model of the bridge and simulation of the wind field of the bridge site in a large boundary wind tunnel at Tongji University, Shanghai, China, some main results about the wind resistant properties of the bridge including aerodynamic instability, buffeting responses both being in operation and erection stages by using of a full aeroelastic model wind tunnel testing are introduced. Some of analytical approaches to those aerodynamic behaviours are also presented, and compared with experimental data of the testing.

• Wind and Structures
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• 제29권1호
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• pp.55-64
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• 2019

The effect of vortex impingement on the fluid dynamics around a cylinder submerged in the wake of another of different diameters is numerically investigated at a Reynolds number Re = 200. While the diameter (D) of the downstream cylinder is fixed, impinging vortices are produced from the upstream cylinder diameter (d) varied as d/D = 0.24, 0.4, 0.6, 0.8 and 1.0, with a spacing ratio L=5.5d, where L is the distance between the center of the upstream cylinder to the front stagnation point of the downstream cylinder. Two-dimensional simulations are carried out using the finite volume method. Fluid forces acting on the two cylinders are correlated with impinging vortices, vortex shedding, and wake structure. Different facets of wake formation, wake structure, and flow separation and their connections to fluid forces are discussed.

• Wind and Structures
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• 제13권6호
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• pp.557-580
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• 2010

A new inflow turbulence generation method and a combined dynamic SGS model recently developed by the authors were applied to evaluate the wind effects on 508 m high Taipei 101 Tower. Unlike the majority of the past studies on large eddy simulation (LES) of wind effects on tall buildings, the present numerical simulations were conducted for the full-scale tall building with Reynolds number greater than $10^8$. The inflow turbulent flow field was generated based on the new method called discretizing and synthesizing of random flow generation technique (DSRFG) with a prominent feature that the generated wind velocity fluctuations satisfy any target spectrum and target profiles of turbulence intensity and turbulence integral length scale. The new dynamic SGS model takes both advantages of one-equation SGS model and a dynamic production term without test-filtering operation, which is particular suitable to relative coarse grid situations and high Reynolds number flows. The results of comparative investigations with and without generation of inflow turbulence show that: (1) proper simulation of an inflow turbulent field is essential in accurate evaluation of dynamic wind loads on a tall building and the prescribed inflow turbulence characteristics can be adequately imposed on the inflow boundary by the DSRFG method; (2) the DSRFG can generate a large number of random vortex-like patterns in oncoming flow, leading to good agreements of both mean and dynamic forces with wind tunnel test results; (3) The dynamic mechanism of the adopted SGS model behaves adequately in the present LES and its integration with the DSRFG technique can provide satisfactory predictions of the wind effects on the super-tall building.

• 대한토목학회논문집
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• 제26권6B호
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• pp.605-612
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• 2006

본 연구(II)에서는 2002년 8월 집중호우시 낙동강 유역에 대하여 강우예측 신경망 모형을 적용하였다. 예측된 3시간 선행 강우량은 실제 관측된 강우량의 패턴을 잘 따르고 있었으며, 기존의 연구와 비교하여 선행시간을 감안하면 강우예측의 정확성이 향상되었음을 확인할 수 있었다. 또한 동일한 유역의 실제 제방붕괴에 따른 범랑양상을 모의하였다. 이때 예측된 강우량 자료는 유역에서의 홍수량 산정을 위한 기본자료로 이용되었으며, 유역에서의 홍수량은 하도 및 제내지에서의 홍수범람 모의를 위한 경계조건으로 이용되었다. 모의결과는 실제 범람흔적과 하천에서의 홍수위 자료와 비교하여 잘 일치되고 있음을 확인할 수 있었다. 본 연구를 통해서 집중호우나 태풍과 같은 이상강우의 강우예측에 대한 인공위성 자료의 실질적인 활용성을 제공하였으며, 위성자료를 이용한 강우예측 기법과 연계하여 국내 실정에 맞는 홍수유출 및 홍수범람 모형의 개발을 통합함으로써 홍수재해에서의 강우, 유출, 범람에 대한 체계적인 실무적용에 사용될 수 있을 것으로 판단되었다.

• 한국수자원학회논문집
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• 제57권7호
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• pp.451-460
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• 2024

빈발하고 있는 도시 지역 침수 피해의 원인을 분석하고 대책을 수립하기 위하여 합리적인 도시 침수 모의 방법을 적용할 필요가 있다. 기존의 국내 연구들은 하수 관거의 맨홀 범람과 하천의 범람 결과를 2차원 범람 유동 모의 모형에 입력하여 침수 모의를 수행하였다. 그렇지만 하천과 맨홀 범람의 침수 모의는 결합하여 분석하는 것이 합리적이다. 이 연구에서는 XP-SWMM을 구성하는 TUFLOW 모듈의 1-2차원 연계 기능을 사용하여 하천과 제내지의 복합 침수 모의를 수행하였다. 해당 방법을 2022년 9월 5일과 6일 태풍 힌남노로 인한 내수 침수와 하천 범람이 동시에 발생한 경상북도 포항시 냉천 하류 유역에 적용하여 적절성을 검증하였다.