• Journal of Ocean Engineering and Technology
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• v.24 no.1
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• pp.60-67
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• 2010

Recently, there has been an increase in the construction of various types of coastal structures for efficient wave dissipation, seawater exchange, and so on. Among these, a perforated slit caisson has been widely used to reduce the reflected wave energy and the wave pressure on the structure. Therefore, many studies on the wave force on a caisson, as well as the wave reflection from it, have been carried out with laboratory experiments and numerical analyses, considering it as a 2-D problem. However, because a structure like a perforated slit caisson has a variable 3-D shape, waves forces should be considered as a 3-D problem. Therefore, in this paper, a fully-nonlinear 3-D numerical model (LES-WASS-3D) is proposed to examine the reflection characteristics of a perforated slit caisson with two chambers. The numerical model, LES-WASS-3D, was verified in a 3-D wave field by a comparison with existing experimental data for wave reflection coefficients. Then, using the numerical results, the reflection from a perforated slit caisson with two chambers was examined in relation to wave steepness, chamber width, and the shape/porosity of perforated slit.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.3
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• pp.181-190
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• 2010

In case of constructing submerged breakwaters, the circulation current is occurred around the open inlet because of mean water level difference between front and rear sides of them. The aim of this study is to investigate the flow control structure of new-type submerged breakwater which is able to reduce mean water level at rear side of it. At first, the numerical model (LES-WASS-3D) is validated by comparing with existing experimental data. And then, numerical simulation is carried out to examine wave height, mean water level and mean flow around the newtype submerged breakwater. From the numerical results, it can be pointed out that the new-type submerged breakwater with drainage system reduces the rip current around the open inlet.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.944-951
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• 2011

This paper reports results of a joint experimental and numerical investigation of the causes of near-transducer errors due to the combined effect of acoustic and ADCP-induced flow disturbance near the ADCP transducer. The laboratory study focused on an isolated ADCP (deployment without boat). Measurements of the flow disturbance produced by the ADCP in vertical and horizontal planes were obtained acquiring measurements with an Acoustic Doppler Velocimeter (ADV). Concurrent measurements with ADCP and ADV were made to infer additional near-transducer effects in the ADCP measurements. The numerical investigation was designed to extend the inquiry on the near-transducer potential errors when the ADCP is deployed from a boat. Large Eddy Simulation (LES) was conducted to obtain the extent and magnitude of the disturbances induced by the drag acting on a boat-mounted ADCP and by the blockage effect of the instrument and boat. It is found the velocities measured by the ADCP are biased low and differ substantially from the undisturbed channel flow solution within a limited layer beneath the instrument.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6305-6314
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• 2015

This study presents numerical simulations of mean flow and turbulence structure of an open channel with submerged vegetation. Filtered Navier-Stokes equations are solved using large-eddy simulation (LES). The immersed boundary method (IBM) is employed based on a Cartesian grid. The numerical result is compared with experimental data of Liu et al. (2008) and shows that simulated results coincided reasonably with experimental data within the average error of 10%. Strong vortices are generated at the interface between vegetated and non-vegetated regions with spanwise extent. The generation of turbulence induced by shear at the interface is interfered with wake turbulence, resulting turbulence intensity maximum. Turbulence produced by shear affects the flow in vegetated region and the penetration depth increases with an increase in the submergence ratio. This result can be used to understand sediment transport mechanisms in the vegetated region.

• Journal of Aerospace System Engineering
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• v.13 no.1
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• pp.1-10
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• 2019

The flow characteristics in a stirred tank are very useful in a wide variety of industrial applications. Generally, the flow pattern, power consumption and mixing time in stirred vessels depend not only on the design of the impeller, but also on the tanks' geometry and internal structure. In this study, the analysis of an unstable and unsteady complicated flow characteristics generated by the interaction between the baffle shape and impeller were performed using the ANSYS FLUENT LES Turbulence Model. The study compared the predictions of CFD with the interaction between two types of rotating impellers (axial and radial flows) and the shapes of three baffles. The results of the comparison verified that the design model showed a relatively efficient trend in the mixing flow fields and characteristics around the impeller and baffles during agitation.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.77-87
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• 2018

In the case of high-energy line breaks in nuclear power plants, supersonic steam jet is formed due to the rapid depressurization. The steam jet can cause impingement load on the adjacent structures, piping systems and components. In order to secure the design integrity of the nuclear power plant, it is necessary to evaluate the load characteristics of the steam jet generated by high-energy pipe rupture. In the design process of nuclear power plant, jet impingement load evaluation was usually performed based on ANSI/ANS 58.2. However, U.S. NRC recently pointed out that ANSI/ANS 58.2 oversimplifies the jet behavior and that some assumptions are non-conservative. In addition, it is recommended that dynamic analysis techniques should be applied to consider transient load characteristics. Therefore, it is necessary to establish an evaluation methodology that can analyze the dynamic load characteristics of steam jet ejected when high energy pipe breaks. This research group has developed and validated the CFD analysis methodology to evaluate the transient behavior of supersonic impinging jet in the previous study. In this study, numerical study on the transient load characteristics of supersonic steam jet impingement was carried out and amplitude and frequency analysis of transient jet load was performed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.115-123
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• 2008

In the present study, a three dimensional hydrodynamic characteristics around the fully submerged dual breakwaters with a sand beach has been investigated numerically using a 3-D numerical scheme, which can determine the eddy viscosity with LES turbulence model and is able to consider wave-structure-seabed interaction in 3-dimensional wave field (LES-WASS-3D), recently developed by Hur and Lee (2007). Based on the numerical experiments, strong vortices can be generated fore and aft edges of the structures, and propagate lee sides. Thus relatively large circulation flows are occurred around submerged breakwaters. The 3-D flow hydrodynamic characteristics have been examined by mean flows and mean vortices for various x-y, x-z sections and y-z layers. Wave height distribution and wave set-up around and over submerged breakwaters, and breaking point migration toward shore side is discussed in detail.

• Cross-Cultural Studies
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• v.44
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• pp.315-342
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• 2016

There exists a general misunderstanding of the Musical as being both a dramatic genre and a musical genre. This misunderstanding lies in the fact that music fills the role of the drama. In other words, there exist a series of narrative episodes that help the development of the drama and music generates the ambience that corresponds to each episode. In this case, music is subordinated to the drama and thus becomes secondary. However, this paper seeks to show that in the Musical, musical composition is so strongly linked to the development of the drama that it is through the musical development that the drama unfolds. This paper seeks to explore this view through one of the most successful musicals of our time, Les $Mis{\acute{e}}rables$. A musical adapted from a novel is not the retrenchment of a series of episodes from the original novel. The process of dramatizing the novel compels the musical creators to observe what to draw out as a dramatic action. The interesting points of a musical consist of how the musical creator has reflected his understanding of the fiction through the composition of the music. This is why this paper has created a table analyzing the forty musical compositions in Les $Mis{\acute{e}}rables$. This table is meant to visualize the musical motifs employed in this play in order to explain the relationship between the musical composition and the development of the drama. The theme of Les $Mis{\acute{e}}rables$ lies in the transformation of Jean Valjean. His change includes the process of transformation from a thief to finding Jesus and his denial of being a sinner to his confessions of sinning. This paper explores the transformation of the dramatic action of Jean Valjean, which is symbolized by such themes as Misery, Love and Name established in musical form. The dramatic conflict between Jean Valjean and Javert as well as between Jean Valjean and $Th{\acute{e}}nardier$ is also explored through the composition of music. The success of Les $Mis{\acute{e}}rables$ lies in its successful constitution of music that embodies the in depth interpretation of the original play.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.270-273
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• 2012

오픈 소스인 FDS(fire dynamic simulator)는 건물, 터널내의 화재나 연기, 열기류의 거동을 연구하기 위하여 국내외적으로 광범위하게 이용되고 있다. 체계적인 연구와 확장이 가능하도록 소스코드와 프로그램구조, 각종 메뉴얼을 갖추고 있으며 향후 개발 방향을 온라인을 통해서 소스코드와 함께 공개하고 있다. 비압축성 비정상해석을 근간으로 하고 있으며 난류유동을 해석할 수 있도록 DNS와 LES모델을 가지고 있다. 화재, 연소, 스프링클러, 화재 확산 등의 모델링을 제공하고 있다. 이러한 모델을 바탕으로 다양한 시나리오의 재난, 피난에 적용할 수 있다. 향후 이러한 기본 모델을 바탕으로 새로운 재난 시나리오에 따라 새로운 알고리즘의 적용하기 위해서는 FDS 기본적인 구조와 모델, 그리고 한계점을 이해할 필요가 있다. 본 연구에서는 이러한 FDS모델을 더욱 확장하기 위한 일환으로 FDS(V5.5.3)의 기본적인 구조을 파악하고 몇 가지 검증모델(verification)에 적용하였다. 또한 이를 향후 FDS의 소스코드를 확장할 수 있는 근간으로 삼고자 한다.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.424-427
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• 2012

본 연구에서는 최근 증가하고 있는 대심도역사의 제연팬 용량에 따른 연기확산영향에 대하여 분석하였다. 시뮬레이션모델은 신금호 역사(5호선, 깊이 46m)를 대상으로 하였으며, 제연팬 용량에 따른 연기확산 영향을 분석 하였다. 현장조사 및 실측을 통하여 계측된 실제 역사의 제연팬에 관한 데이터를 화재시뮬레이션 조건으로 적용하였다. 역사전체를 해석 대상으로 하여 총 400만개의 격자를 사용하였으며, 제연팬 용량에 따른 연기확산 영향 비교를 위하여 화재 시나리오를 작성하여 Case별로 화재해석을 수행하였다. 계산 효율을 높이기 위하여 MPI병렬처리기법을 사용하였으며 해석코드는 LES(large eddy simulation) 기법을 주로 사용하는 FDS5 code를 사용하였다.