• 해양환경안전학회지
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• 제28권7호
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• pp.1244-1251
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• 2022

지난 10년간 선박의 횡동요 복원력 상실에 의한 해양사고가 지속해서 증가하고 있어, 횡동요 운동을 효과적으로 줄일 수 있는 장치가 필요한 실정이다. 횡동요 감쇄 탱크는 단순한 설치만으로 횡동요 저감을 가져오는 대표적인 수동형 제어장치로 그 장점이 널리 알려져 있다. 따라서 본 연구에서는 U-튜브형 횡동요 감쇄 탱크의 수치해석 기법을 개발하고자 한다. 특히, 해석기법의 검증을 위해 자유수면 높이를 실험을 통해 계측하였다. 수치해석기법은 메쉬 의존성, 난류모델 (k-𝜖, k-𝜔, Reynolds Stress Model), 시간 간격 크기 및 반복횟수 등의 영향을 비교하여 개발하였다. 최종적으로 개발된 해석기법은 Realizable k-𝜖이 난류 모델에 10-2s 수준의 시간 간격 크기와 15회의 반복횟수를 적용하였다. 2가지의 U-튜브형 감쇄 탱크의 조건에서 계측된 자유수면 높이를 이용하여 개발된 해석기법을 검증하였다. 본 연구의 수치해석은 RANS 기반 상용 해석 Solver인 STAR-CCM+ (ver. 17.02)을 이용하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 제5회 압연심포지엄 신 시장 개척을 위한 압연기술
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• pp.223-230
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• 2004

In order to improve the productivity and quality of the hot rolled products, many morden mills have continuously required advanced roll materials. The introduction of HSS rolls in early stands of the Hot Strip Mill brought the excellent performance in wear resistance and surface roughness. Ni-grain rolls used in the later stands was needed to improve the roll performance. Therefore, the carbide reinforced Ni-grain roll was developed. The present paper will describe the development of carbide reinforced rolls made by INI STEEL and the results of mill tests. The wear resistance was increased upto $40\%$ and the anti-accident ablility was remarkably improved compared to the normal Ni-rain roll.

• 조명전기설비학회논문지
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• 제18권3호
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• pp.74-80
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• 2004

연속 주조 공정에서 설정한 속도로 주편을 인발하는 스트랜드 구동롤에 인발력이 적절하게 분배가 되지 않으면 주형 레벨의 주기적인 변동을 유발시킴과 동시에 주편의 품질을 저하하게 된다. 따라서 본 논문에서는 주편의 속도를 제어함과 동시에 각 구동롤에 운전자가 원하는 비율로 인발력을 분배할 수 있는 알고리즘을 제안한다. 제안된 방법은 전동기에 작용하는 토크 전류를 상위 제어기로 귀환하여 평균 토크 전류를 산출하고 각 구동롤 전동기의 토크 전류와 비교하여 전동기의 속도 기준값을 미소하게 변경함으로써 각 구동롤 전동기의 토크 전류가 평균 토크 전류에 추종하도록 하여 인발력을 분배한다. 그리고 과도상태 개선을 위하여 안티와인더업(anti-wind up) 제어기를 가진 인발력 제어기를 적용하였으며, 제안된 알고리즘의 확인을 위하여 포스코의 시험연주기에 적용하여 우수성을 입증하였다.

• 한국정밀공학회지
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• 제32권8호
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• pp.673-680
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• 2015

A roll-to-roll (R2R) continuous manufacturing system for a carbon-nanotube (CNT)-/silver-nanowire (AgNW)- based large-area transparent conductive film was introduced in this study. The systemic guidelines of the R2R slot-die coating process including roll eccentricity, wrap angle, pump accuracy, and blower influence were discussed. To simulate the coating phenomenon, we investigated the governing parameters of the coating process by incorporating the estimated relative thickness that was defined by combining the viscocapillary model and volume model. By using experimental and mathematical approaches, an excellent transparent conductive layer with a $40{\Omega}/{\Box}$ sheet resistance and 88 % transmittance was obtained; moreover, a dimensionless number identifies the correlation between the transparent conductive film and the anti-reflection film.

• 한국기계가공학회지
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• 제12권5호
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• pp.16-22
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• 2013

A two-dimensional photonic crystal structure was investigated using a roll-to-roll nanoreplication and physical vapor deposition processes for the inexpensive enhanced fluorescence substrate which is not sensitive to the polarization directions of excitation light source. An 8 inch silicon master having nano dot array with a diameter of 200 nm, a height of 100 nm and a pitch of 400 nm was prepared by KrF laser scanning lithography and reactive ion etching processes. A flexible polymer mold was fabricated by flat type UV replication process and a deposition of 10 nm nickel layer as an anti-adhesion layer. A roll mold was prepared by warping the flexible polymer mold on an aluminum roll base and a roll-to-roll UV replication process was carried out using the roll mold. After the deposition of ~ 100 nm $TiO_2$ layer on the replicated nano dot array, a 2 dimensional photonic crystal structure was realized with a resonance wavelength of 635 nm for both p- and s-polarized light sources.

• 대한조선학회논문집
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• 제52권6호
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• pp.452-459
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• 2015

It is important to use bench test results in the design process of anti-rolling tanks. Traditional bench tester is usually designed to perform only roll motions about a fixed axis and relatively small so that the viscous effects may not be neglected. Novel bench tester which could adjust the motion center to realize the coupled motion of sway and roll has been devised and manufactured therefore, large scaled bench tester could be utilized for designing the passive anti-rolling tanks. The time history of the reference signal from the rotation sensor of the bench tester have been recorded and processed to determine the phase angle to derive the Response Amplitude Operator(RAO) of the stabilized ship. The breadth of ART tank model should be large up to 2 m to diminish viscous scale effect and the vertical position of the tank can be varied with the ship's center of motion. The periods and the amplitude of roll motion can be varied from 1.5 sec to 5 sec and up to ±20°, respectively. The components of the tester was expressed in three dimensional digital mockup (DMU) and assembled together in the CAD space. The final configuration of the bench tester has been determined by confirming the smooth operation of the moving parts without interference through the animation in CAD space. New analytic logic are introduced for the determination of hydrodynamic moment and phase difference due to fluid motion in ART and verified through the test. The developed bench tester is believed to be effective and accurate for the verification of stabilization effect of ART taking into the consideration of the sway effect in the design stage.

• Journal of Ship and Ocean Technology
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• 제7권1호
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• pp.19-28
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• 2003

The systematic results of anti-rolling tanks tests obtained by bench tester and roll test in towing tank have been examined. The effects on the oscillating period of fluid transfer through the duct of U-tube tank due to damper plates and the effects on roll damping moment of the tank due to swash plates are alto evaluated from the results. A simple control algorithm for a forced fluid transfer in U-tube tanks if devised to active operation of the tank by air blower. The active performances of the tank are confirmed very effective through the tank tests carried out in the irregular waves.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.70-75
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• 2001

Intensive experimental investigations were carried out to provide information of the effects of inflow on the rolling characteristics and stability of ships, which becomes great concern in relation to ship's capsizing. A series of systematic experiments have been performed considering the effects cf combined motion of roll-heave-sway and relevant parameters, such as roll angle and period, tank water height etc. To accommodate this type of experiments with 3-degree of freedom of motion, a bench tester has been developed and verified using existing data. Also, theoretical application of anti-roll tank has been incorporated to support the process of investigation. A model of Ro-Ro ships is used in the present study as this type of vessels, as well as fishing vessels, with large open decks, can loose stability rapidly when there is inflow on the decks.

• 한국항해항만학회지
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• 제34권4호
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• pp.271-279
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• 2010

The Mobile Harbor(MH) is a new transportation platform that can load and unload containers to and from very large container ships in the sea. This loading and unloading by crane can be performed with only very small movements of the MH in waves because MH is operated outside of the harbor. For this reason, an anti-rolling tank(ART) and an active mass driving system(AMD) were designed to reduce MH's roll motion, especially at the natural frequency of MH. In the conceptual design stage, it is difficult to confirm the design result of theses anti-rolling devices without modeling and simulation tools. Therefore, the coupled MH and anti-rolling devices' dynamic equations in waves were derived and a simulation program that can analyze the roll reduction performance in various conditions, such as sea state, wave direction, and so on, was developed. The coupled equations are constructed as an eight degrees of freedom (DOF) motion that consists of MH's six DOF dynamics and the ART's and AMD's control variables. In order to conveniently include the ART's and AMD's control dynamics in the time domain, MH's radiated wave force was described by an impulse response function derived by the damping coefficient obtained in the frequency domain, and wave exciting forces such as Froude-Krylov force and diffraction force and nonlinear buoyancy were calculated at every simulation time interval. Finally, the roll reduction performances of the designed anti-rolling devices were successfully assessed in the various loading and wave conditions by using a developed simulation program.

• Structural Engineering and Mechanics
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• 제68권1호
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• pp.1-15
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• 2018

In ocean industry, free surface type ART (Anti Roll tank) system has been widely used to suppress the roll motion of floating structures. In those, various obstacles have been devised to obtain the sufficient damping and to enhance the controllability of freely rushing water inside the tank. Most of previous researches have paid on the development of simple mathematical formula for coupled ship-ARTs analysis although other numerical and experimental approaches exist. Little attention has been focused on the use of 3D panel method for preliminary design of free surface type ART despite its advantages in computational time and general capacity for hydrodynamic damping estimation. This study aims at developing a potential theory based hydrodynamic code for the analysis of floating structure with baffled ARTs. The sloshing in baffled tanks is modeled through the linear potential theory with FE discretization and it coupled with hydrodynamic equations of floating structures discretized by BEM and FEM, resulting in direct coupled FE-BE formulation. The general capacity of proposed formulation is emphasized through the coupled hydrodynamic analysis of floating structure and sloshing inside baffled ARTs. In addition, the numerical methods for natural sloshing frequency tuning and estimation of hydrodynamic damping ratio of liquid sloshing in baffled tanks undergoing wave exiting loads are developed through the proposed formulation. In numerical examples, effects of natural frequency tuning and baffle ratios on the maximum and significant roll motions are investigated.