• Title, Summary, Keyword: 오픈폼

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Numerical Study on Roughness Effect for Axi-symmetry Submerged Body in High Reynolds Number (고 레이놀즈 수에서의 축대칭 몰수체의 거칠기에 대한 수치연구)

  • Joung, Tae-Hwan;Song, Hyung-Do;Yum, Jong-Gil;Song, Seongjin;Park, Sunho
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.24 no.2
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    • pp.246-252
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    • 2018
  • In this paper, the friction drag force of 3D submerged body is investigated by considering the surface roughness, the first grid height, and the Reynolds number using open CFD source code, OpenFOAM 4.0. A procedure for estimating drag components by CFD code is set up and suggested in this study. In the 3D submerged body, because of the form factor in the 3D computations, the friction resistance with the small roughness of $12{\mu}m$ obtains different result with the smooth wall. As the Reynolds number increased, the boundary layer becomes thinner and the fiction resistance tends to decrease. In the computations for the effect of y+, the friction resistance and wall shear stress are excessively predicted when the y+ value deviates from the log layer. This is presumably because the boundary layer becomes thicker and the turbulence energy is excessively predicted in the nose due to the increase in y+ value. As the roughness increases, the boundary layer becomes thicker and the turbulence kinetic energy on the surface increases. From this study, the drag estimation method, considering the roughness by numerical analysis for ships or offshore structures, can be provided by using the suggested the y+ value and surface roughness with wall function.

Grid Tests for Large Eddy Simulation of Transitional Flows around Turbulence Stimulators (난류 촉진기 주위 천이 유동의 대형 와 모사를 위한 격자 테스트)

  • Lee, Sang Bong;Park, Dong Woo;Paik, Kwang-Jun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.23 no.1
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    • pp.112-121
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    • 2017
  • Large eddy simulations of transitional flows around a stud installed on a flat plate have been performed to investigate an influence of grid resolution on turbulence stimulation by the stud. Because streamwise vortical structures generated by the stud played an important role in turbulence stimulation of boundary layer, streamwise vorticity was compared in the wake region behind the stud when the number of grids increased or decreased by a ratio of ${\sqrt{2}}$ in streamwise, wall-normal and spanwise directions respectively. The streamwise vorticity was shown to be mainly affected by spanwise grid resolution (${\Delta}z^+$) rather than streamwise and wall-normal grid resolution. In a viewpoint of numerical efficiency as well as physical resolution, ${\Delta}x^+{_{min}}=7.6$, ${\Delta}x^+{_{max}}=41$, ${\Delta}y^+{_{wall}}=0.25$ and ${\Delta}z^+=7.6$ was found to be desirable. Once a grid resolution was determined in each direction, a grid verification was carried out by increasing or decreasing the grid resolution y a ratio of ${\sqrt{2}}$ in all directions. The grid uncertainties of pressure and drag coefficients were 21.6 % and 2.8 % while the corrected uncertainties were 2 % and 0.3 %, respectively.

Omni Channel System for Efficient Fitting Service and Shipping Process (효율적인 피팅 서비스와 배송 프로세스를 위한 옴니채널 시스템에 대한 연구)

  • Lim, Ji-yong;Oh, Am-suk
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.21 no.2
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    • pp.373-378
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    • 2017
  • While on-line shopping markets are growing, consumer's procurement processes are being confused regardless of on or off line market and, smart consumers who want intelligent tailored services have emerged. Depending on the changeable pattern of consumer, most of related companies provide various Omni channel and O2O service. However, reactions of the fashion companies are tend to be late. Recently, the IoT environment has changed to standards-based open platform and it requires a variety of intelligent services depending on the type of environment and objects. This thesis proposes fashion O2O system using smart fitting display that is adaptable to fashion companies. This proposed system provides fitting information which is performed on off-line by users after constructing the database, it also support the works as on-line status, thus, it makes users' procurements to maintain continuously. For the more, customer oriented intelligent fitting service would be expected by the information connection with the shop and delivery systems.

A Smart Antenna System API and Smart Antenna BTS Open Architecture for SDR Network (SDR 네트워크를 위한 스마트 안테나 시스템 API 및 스마트 안테나 기지국 오픈 아키텍처)

  • Ryu, Nam-Gyu;Choi, Seung-Won
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.4A
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    • pp.335-341
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    • 2008
  • The SDR(Software Defined Radio) system for hardware and software must be an open structure to various system standards. It should also provide a capability of distributed processing, object-orientedness, and software controllability. It implies that the software to be used in the SDR system should provide the openness such that it can operate independently of a given hardware platform. In order to achieve these goals, the SDR system tends to modularization for increasing hardware reuse and design flexibility, which provides the system reconfigurability. In this paper, we implemented a base station with proposed an open architecture of a Smart Antenna Base Station(SABS) and Smart Antenna APIs[10] operating in SDR network in such a way that the architecture itself is suitable for the entire system to maintain the openness, object-orientedness, and software controllability.