• 한국해양공학회지
• /
• 제29권2호
• /
• pp.191-198
• /
• 2015

In this study, we proposed a new type of dual-buoy wave energy converter (WEC) exploiting multi-resonance and analyzed the experimental results from a model test in a 2-D wave flume. A dual-buoy WEC using multi-resonance has two advantages: high efficiency at the resonant frequencies and the potential to extend the frequency range available to extract wave power from the WEC. The suggested WEC was composed of an outer buoy and an inner buoy sliding vertically inside the outer buoy. As the power take-off device, a linear electric generator (LEG) consisting of permanent magnets and coils fixed at each buoy was adopted. Electricity was produced by the relative heave motion between the two buoys. To search for the optimal shape of a dual-buoy WEC, we conducted experiments on the heave motion of a two-body system in regular waves without an LEG installed. Model tests with six combinations of experimental models were conducted in order to find the motion characteristics of a dual-buoy WEC. It was found that model 2, which included a ring-shaped appendage to move the resonant frequency of the outer buoy toward a high value, showed a higher relative heave response amplitude operator (RAO) curve than model 1. In addition, the double-peak shape of the heave RAO curve shown for model 2 indicated the extension of the frequency range for extracting wave power in irregular waves.

• 한국해양공학회지
• /
• 제33권2호
• /
• pp.131-138
• /
• 2019

This study focused on the roll motion characteristics of a two-dimensional (2D) rectangular floating structure under regular beam sea conditions. An experiment was conducted in a 2D wave tank for a roll free decay test in calm water and the roll motion in a range of regular waves with and without heave motion to investigate the motion response and heave influence on the roll motion. A numerical study was carried out using Reynolds-averaged Navier Stokes (RANS)-based CFD simulations. A grid convergence test was conducted to accurately capture the wave condition on the free surface based on the overset mesh and wave forcing method. It was found in the roll free decay test that the numerical results agreed well with the experimental results for the natural roll period and roll damping coefficient. It was also observed that the heave motion had an impact on the roll motion, and the responses of the heave and roll motion from the CFD simulations were in reasonable agreement with those from the experiment.

• 한국지반공학회논문집
• /
• 제23권5호
• /
• pp.43-51
• /
• 2007

동결작용은 빌딩, 구조물, 도로, 철도 그리고 공공시설관로에 엄청난 손상을 일으킬 것이다. 자연지반의 동상에 대한 연구는 과거에 많이 수행되었다. 근래에는 사회기반시설 유지의 발전과 함께 각종구조물의 복잡화로 인하여 동상대책에 대한 관심이 집중되고 있다. 본 연구에서는 구조물에 작용하는 자연지반의 동상력을 정량적으로 파악하는 것을 목적으로 하였다. 지표면에 설치한 원형강판에 작용하는 동상력이 현장시험에서 측정되었다. 동결면에서 발생하는 동상력은 동결된 토층을 거쳐 구조물에 전달된다. 또한 다단앵커로 보강된 옹벽이 현장에 설치되고 옹벽에 작용하는 동결선과 동상압 등이 측정되었다. 최종적으로 동결면의 위치와 형상이 수치해석수법을 이용하여 추정되었고 치환 범위를 결정하는 설계수법이 토질정보와 기상정보에 따라 제안되었다.

• 한국해양공학회지
• /
• 제25권2호
• /
• pp.36-46
• /
• 2011

A two-dimensional floating body with a moon pool under forced heave motion, including a piston mode, is numerically simulated. A dynamic CFD simulation is carried out to thoroughly investigate the flow field around a two-dimensional moon pool over various heaving frequencies. The numerical results are compared with experimental results and a linear potential program by Faltinsen et al. (2007). The effects of vortex shedding and viscosity are investigated by changing the corner shapes of the floating body and solving the Euler equation, respectively. The flow fields, including the velocity, vorticity, and pressure fields, are discussed to understand and determine the mechanisms of wave elevation, damping, and sway force.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2000년도 가을 학술발표회 논문집
• /
• pp.447-454
• /
• 2000

This paper presents fundamental characteristics of a copper slag when used geotechnical materials. For this study, it was conducted laboratory tests such as compaction, large direct shear, hydraulic conductivity, leaching, TDR, frost heave test and so on. The results of laboratory tests shown gradually increase in draining capacity and shearing resistance more slag mixing. The unfrozen water in temperature changes and frost heave amounts in condition of -17 $^{\circ}C$ appeared to decrease. Also, toxicity tests based on the domestic solid waste regulations were satisfied with nonhazardous. By this research results, a copper slag mixed with granite soil may been used as granular base and embankment materials, fill etc.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
• /
• 제4권1호
• /
• pp.1-9
• /
• 2001

An oscillating body motion with extremely large amplitude has been studied using the viscous flow solver. Time simulations of oscillating ship hull in prescribed heave and roll motions are presented using RANS method with FAM approach (Chen, 1995). For viscous flows, laminar flow and turbulent flow with $textsc{k}$-$\varepsilon$ model are considered and compared. The viscous flow solver of RANS method is performed together with a Chimera type of multi-block grid system to demonstrate the advantage of accurate and efficient zonal approach. In the present study, effects of viscosity and oscillation degree are discussed using Re=1000 and Re=1000000. Large motion of oscillating body shows clear vortex propagation that is not possible for inviscid flow to present.

• Ocean Systems Engineering
• /
• 제9권1호
• /
• pp.1-19
• /
• 2019

Latching control was applied to a Wave Energy Converter (WEC) buoy with direct linear electric Power Take-Off (PTO) systems oscillating in heave direction in waves. The equation of the motion of the WEC buoy in the time-domain is characterized by the wave exciting, hydrostatic, radiation forces and by several damping forces (PTO, brake, and viscous). By applying numerical schemes, such as the semi-analytical and Newmark ${\beta}$ methods, the time series of the heave motion and velocity, and the corresponding extracted power may be obtained. The numerical prediction with the latching control is in accordance with the experimental results from the systematic 1:10-model test in a wave tank at Seoul National University. It was found that the extraction of wave energy may be improved by applying latching control to the WEC, which particularly affects waves longer than the resonant period.

• 한국터널지하공간학회 논문집
• /
• 제20권1호
• /
• pp.183-195
• /
• 2018

최근 공동구 및 지하터널의 수요증가와 함께 수직구 굴착에 대한 연구의 필요성이 증가하고 있다. 공동구 연구단은 국토교통부 연구개발사업의 일환으로 '수직구 외주면 선행 굴착공법 및 장비'를 개발하였으며 현재 성능 검증 중에 있다. '수직구 외주면 선행 굴착공법'은 수직구 굴착 시 굴착면의 외주면을 먼저 굴착하고 굴착기 벽체를 관입시켜 연약지반의 히빙에 대한 지반의 안정성을 확보하는 공법이다. 이 연구에서는 원심모형실험을 통해 히빙을 모사하고 관내토의 유무에 따른 지반면의 히빙과 지반침하, 그리고 주변지반의 거동을 비교, 분석하였다. 분석 결과 관내토가 지반침하와 히빙의 발생을 충분히 억제하는 효과를 나타내는 것으로 파악되었으며, 수직구 외주면 선행 굴착공법이 히빙에 대한 지반의 안정성을 충분히 확보함을 확인할 수 있었다.

• Journal of applied mathematics & informatics
• /
• 제23권1_2호
• /
• pp.127-140
• /
• 2007

We present the boundary value problem (BVP) for the heave motion due to a vertical circular cylinder in water of finite depth. The BVP is presented in terms of velocity potential function. The velocity potential is obtained by considering two regions, namely, interior region and exterior region. The solutions for these two regions are obtained by the method of separation of variables. The analytical expressions for the hydrodynamic coefficients are derived. Computational results are presented for various depth to radius and draft to radius ratios.

• 센서학회지
• /
• 제17권6호
• /
• pp.454-461
• /
• 2008

This embedded module measures significant wave height and zero crossing periods through spectral energy from a record of time series heave motion. An ARM7TDMI core microcontroller serves as the main control unit which performs the appropriate control and signal conditioning. Monitored wave characteristic is transmitted with satellite modem. Mathematical equations on signal conditioning and experiments procedures are documented in this paper.