Experimental and numerical investigation of a surface-fixed horizontal porous wave barrier

Poguluri, Sunny Kumar,Kim, Jeongrok,George, Arun,Cho, I.H. Techno-Press 2021 Ocean systems engineering Vol.11 No.1

Experimental and numerical investigations were conducted to study the performance of a surface-fixed horizontal porous wave barrier in regular waves. The characteristics of the reflection and transmission coefficients, energy dissipation, and vertical wave force were examined versus different porosities of the barrier. Numerical simulations based on 3D Reynolds Averaged Navier-Stokes equations with standard low-Re k-ε turbulent closure and volume of fluid approach were accomplished and compared with the experimental results conducted in a 2D wave tank. Experimental measurements and numerical simulations were shown to be in satisfactory agreement. The qualitative wave behavior propagating over a horizontal porous barrier such as wave run-up, wave breaking, air entrapment, jet flow, and vortex generation was reproduced by CFD computation. Through the discrete harmonic decomposition of the vertical wave force on a wave barrier, the nonlinear characteristics were revealed quantitatively. It was concluded that the surface-fixed horizontal barrier is more effective in dissipating wave energy in the short wave period region and more energy conversion was observed from the first harmonic to higher harmonics with the increase of porosity. The present numerical approach will provide a predictive tool for an accurate and efficient design of the surface-fixed horizontal porous wave barrier.

신형식 부방파제의 파랑제어에 관한 연구

김도삼,이광호,최낙훈,윤희면 한국해안해양공학회 2004 한국해안해양공학회 논문집 Vol.16 No.1

본 연구에서는 원전어항에서 채용하고 있는 강제 부방파제에 비해 소요재료량의 변화가 크지 않은 범위에서 전후연직판의 위치와 형식의 변화 및 수평판의 부착 유무에 따른 여러 형식의 부방파제에 의한 투과율과 반사율을 Green 함수법으로부터 계산한 결과에 기초하여, 원전어항의 강제 부방파제보다 단주기파 및 장주기파를 보다 효과적으로 제어할 수 있는 새로운 형식의 부방파제를 검토하였다. 이로부터 연직커튼판 하부에 수평판을 부착한 형태의 부방파제가 파랑제어기능이 우수한 것으로 판명되었고, 이는 원전어항 부방파제보다 파랑제어기능이 탁월하다는 것을 알 수 있었다. 또한, 본체에 부착된 전후연직판 및 수평판의 크기와 간격을 조절함으로써 적합한 투과파를 얻을 수 있다는 것도 알 수 있었다. In this study, several new types of floating breakwater are proposed according to the geometry of the vertical barrier and the existence of horizontal plate, and are compared to the steel floating breakwater adopted in Won-Jun fishing port and the performance of wave control is numerically investigated by using Green function method. From the numerical results, model attached the horizontal barrier under the vertical barrier is more efficient for reflection and transmission coefficient than the steel floating breakwater in Won-Jun fishing port. It is confirmed that the transmitted waves can be controlled efficiently by optimizing the length and distance of a vertical and horizontal barriers.

수평차단막 설치에 따른 랙크식 창고의 화재방호성능 개선에 관한 연구

박문우,홍성호 한국위험물학회 2019 한국위험물학회지 Vol.7 No.2

A rack-type warehouse is a structure that vertically loads a large amount of goods. When a fire occurs can cause massive damage. In Korea, rack-type warehouses are installed with sprinklers and fire detectors in accordance with national fire safety codes. In case of rack-type warehouse fires in Korea, sufficient fire protection performance could not be secured. In this study, the horizontal barrier was analyzed by fire simulation to improve the fire protection performance of rack type warehouse. As a result of the fire simulation, it was possible to prevent the vertical spread of the fire when the horizontal barrier was installed over a certain length. In addition, in the case of installing a horizontal barrier and installing fire detectors under the horizontal barrier, it was possible to detect the fire early compared to the existing way of fire detector installation. When the horizontal barrier is installed, the temperature distribution under the horizontal barrier is higher than when the horizontal barrier is not installed, and the sprinkler head can be operated early due to the heat collecting effect.

수평차단막 화재성능 시뮬레이션

짐듀이,김운형,김수진 한국재난정보학회 2019 한국재난정보학회 학술대회 Vol.2019 No.09

Horizontal barriers are included in international standards as a possible component for the protection of rack storage. A definition of horizontal barrier from the NFPA (National Fire Protection Association) 13, Standard for the Installation of Sprinkler Systems, is “A solid barrier in the horizontal position covering the entire rack, including all flue spaces at certain height increments, to prevent vertical fire spread.” As part of the evaluation of rack storage protection, a simulated fire in a double row rack storage arrangement was used to consider the impact the horizontal barrier had on the fire development. The simulation was done with Version 6.7.1 of Fire Dynamics Simulator (FDS) and Four simulations were run. The temperatures, heat release rates, detector actuation times, and sprinkler actuation times are compared for each scenario. The simulation allowed comparison of results for the particular heat release rate and fire growth specified. The horizontal barrier can be a significant factor in providing protection for rack storage.

랙크식 창고 화재의 수직 확산 방지를 위한 수평차단막과 In-Rack 스프링클러 적용에 관한 실험연구

박문우,홍성호,최기옥,최돈묵,김수진 한국안전학회 2019 한국안전학회지 Vol.34 No.5

A rack-type warehouse has the advantage of storing a large amount in a small area by loading goods vertically. But in terms of fire risk, the fire load is very high, which can cause massive damage in the event of a fire. In the United States, research has been actively conducted to minimize the spread of vertical fires, and relevant standards have been established and operated. In Korea, research and related standards are insufficient to prevent the vertical spread of rack-type warehouse fires. In this study, an experimental study was conducted to prevent the vertical spread of a rack-type warehouse fire using a horizontal barrier and in-rack sprinklers. As a result of the test, the horizontal barrier considering the continuous flame prevented the vertical spread of the flame for a certain time. However, the horizontal barrier with continuous flame did not show the effect of preventing continuous flame. The combination of the horizontal barrier and the in-rack sprinkler prevented the vertical spread of fire effectively. In addition, the heat collecting effect through the horizontal barrier was shown and helped the early operation of the in-rack sprinklers.

랙크식 판매시설 내 차단막 형태에 따른 연기흐름과 피난계획에 관한 연구

황금숙(Keum Sook Hwang),김진아(Jin A Kim),장원복(Bok Won Chang) 한국화재소방학회 2023 한국화재소방학회 학술대회 논문집 Vol.2023 No.1

신형식부방파제의 개발과 정온도에 관한 연구

이현진(Lee, Hyun Jin),김도삼(Kim, Do Sam),신문섭(Shin, Moon Seup) 한국해안해양공학회 2013 한국해안해양공학회 논문집 Vol.25 No.3

본 연구에서는 원전부방파제 및 통영부방파제의 단면을 기본형으로 하여 그들의 소요재료량에 비해 변화가 작은 범위내에서 연직커튼판의 모양과 위치의 변화 및 수평판의 부착 유무에 따른 여러 가지 형식의 부방파제를 검토하여 원전부방파제보다 장주기측에서 파랑제어성능이 우수한 신형식부방파제를 고안 및 제안하였다. 그리고, 본 연구의 신형식부방파제를 마산시 원전항에 원전부방파제의 대신에 적용한 경우 보다 장주기파랑을 효과적으로 제어하여 항내전달파고를 저감시키고, 따라서 항내정온도를 향상시킬 수 있다는 것을 확인할 수 있었다. In this study, a new type floating breakwater was proposed to improve the capability of wave attenuation compared with the existing floating breakwater in Wonjun Port, which is located in Masan City, Korea. In order to develop the optimal design, many different configurations considering the shape and location of vertical barrier and horizontal plate were examined based on the shape of existing floating breakwaters in Wonjun and Tongyeong Port. The analytical and numerical results of the new type floating breakwater showed better performance in long-period wave attenuation than the existing floating breakwater in Wonjun. Therefore, the new type floating breakwater can improve harbor tranquility in Wonjun Port.

IP-TV 활성화를 위한 법규제 개선방안

황근(Hwang Kuhn) 서울대학교 공익산업법센터 2008 경제규제와 법 Vol.1 No.2

본 연구는 IP-TV 도입활성화에 필요한 법제도적 현황과 문제점을 살펴보고, 개선방향을 제시하는 데 목적이 있다. 2008년 11월 17일 KT의 실시간 IP-TV를 시작으로 본격적인 IP-TV시대에 들어섰다. 정부의 전폭적인 정책적 지원아래 시작은 일단 순조로워 보인다. 하지만 관련 법제도적 틀은 개선될 부분이 적지 않다. 무엇보다 2007년 제정된‘인터넷 멀티미디어방송사업법(이하 IP-TV법)’자체가 근본적인 문제점을 가지고 있다. IP-TV법은 방송시장의 진입장벽을 우회하기 위한 목적을 담고 있다. 특히 우리나라의 방송시장은 공익을 내세운 유난히 강한 진입장벽을 가지고 있다. 매체간 균형발전, 지역성 구현등을 표방한 지상파 방송재전송 같은 문제는 이전의 신규 미디어들의 시장진입을 어렵게 만들었던 전략적 집입장벽들이었다. 이 때문에 IP-TV법은‘콘텐츠 동등접근’‘지상파방송재전송’등의 규정을 포함하고 있다. 하지만 특별법의 한계로 인해 다른 경쟁매체들과의 공정경쟁를 규율할 수 없는 상태다. 이러한 한계를 극복하기 위해서 궁극적으로 수평적 규제체계를 도입해 공정경쟁과 융합콘텐츠 활성화를 도모할 필요가 있다. This study’s purpose is to law and policy implementation for revitalization of IP-TV. IP-TV, KT Mega-TV, was set up on Nov. 17. Maybe other IP-TV enterprise, LG Telecom, SK Broadband, will start next month. In spite of smoothly introduction of IP-TV, law and regulatory frame is not enough for IP-TV activation. Especially ‘Internet Multimedia Broadcasting Law’, enacted for introduction of IP-TV last year, has many problems. Internet Multimedia Broadcasting Law has a will avoiding the entrance barrier in broadcasting market. It was told that broadcasting market has higher fence than other service market. In Korea, new entrance of broadcasting market is most difficult in the world because of public interest barrier, for example localism, coexistence of media etc.. In the purpose of these, Internet Multimedia Broadcasting includes ‘the equal access of content’ ‘re-transmission of terrestrial broadcasting’ etc.. for fair competition among multi platform broadcasters. But this purpose would not be acquired because Internet Multimedia Broadcasting Law is not applied in other multi platform broadcasters besides IP-TV. For implement of this limit, Convergence Law including broadcasting and telecommunication would have to enact. In conclusion, horizontal regulatory system should be introduced for fair competition and revitalization of convergence media and digital content industry.