• 수산해양기술연구
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• 제34권2호
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• pp.165-173
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• 1998

When an automatic course-keeping is concerned, as is quite popular in modem navigation, the closed-loop steering system consists of autopilot device, power unit (or telemotor unit), steering gear, magnetic or gyro compass and ship dynamics. In order to estimate automatic steering system of ships in open seas. we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, I provide calculation method of imposing irregular disturbance to autopilot navigation system of the ship in open seas, and also show calculation examples about fishing boat. The disturbance consists of the irregular wave and the fluctuating component of wind. Finally, The disturbances are calculated in terms of equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated.

• 해양환경안전학회지
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• 제21권5호
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• pp.591-598
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• 2015

본 연구에서는 태풍 나크리에 의한 해운대 해수욕장의 쇄파대 수리특성을 SWASH 모형을 이용하여 분석하였다. 국립해양조사원에서 제공하는 파랑관측자료를 바탕으로 태풍 나크리 내습 시의 대표파를 선정하였다. 수치모형에서 입사파는 JONSWAP Spectrum에 의한 불규칙파로 선정하였다. SWASH 모형에 의해 산정된 해빈류 패턴은 현지관측자료와 비교하였으며 수치모형에서 산정된 최대소상고는 비디오 모니터링 자료 및 경험식과 비교하였다. 최대소상고의 위치는 비디오 모니터링 자료에 나타난 파흔을 이용하여 유추하였으며 태풍 NAKRI(1412) 내습 시 S 계열의 파랑이 지배적으로 작용하였으며 동백섬측에서 미포측으로 연안류가, 해운대 해수욕장 중앙부근에서 이안류가 발생하였다. SWASH 모형을 이용하여 산정한 최대소상고(1.15 m)는 비디오 모니터링 자료(1.26 m)와 유사한 경향성을 나타냈으며 Stockdon et al.에 의해 제시된 경험식(1.33m)과 비교적 유사하게 나타났다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권1호
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• pp.70-86
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• 2015

Short crested waves play an important role for planning and design of harbours. In this context a numerical simulation is carried out to evaluate wave tranquility inside a real harbour located in east coast of India. The annual offshore wave climate proximity to harbour site is established using Wave Model (WAM) hindcast wave data. The deep water waves are transformed to harbour front using a Near Shore spectral Wave model (NSW). A directional analysis is carried out to determine the probable incident wave directions towards the harbour. Most critical threshold wave height and wave period is chosen for normal operating conditions using exceedence probability analysis. Irregular random waves from various directions are generated confirming to Pierson Moskowitz spectrum at 20m water depth. Wave incident into inner harbor through harbor entrance is performed using Boussinesq Wave model (BW). Wave disturbance experienced inside the harbour and at various berths are analysed. The paper discusses the progresses took place in short wave modeling and it demonstrates application of wave climate for the evaluation of harbor tranquility using various types of wave models.

• 수산해양기술연구
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• 제51권4호
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• pp.504-511
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• 2015

In this paper, the results of evaluating the passenger comfort due to the standard deviation of acceleration in vertical and lateral direction regarding the ship response in irregular wave by ordinary strip method in regular wave and energy spectrum using linear superposition theory in order to evaluate the motion of experimental ship are as follows. According to the results of ship response, it was possible to find that, in order to reduce the motion of ship, a ship operating in bow sea was more stable than in quartering sea. In the results of analyzing the standard deviation of acceleration in vertical direction according to each component wave pattern, when there was a wave length of 56m and an average wave period of 6 sec, most of cases showed the peak value. And among them, the standard deviation was 0.35 which was the highest in head sea. And in case of lateral direction, the maximum value was shown in a wave length of 100m and an average wave period of 8 sec. And it was 0.16 in beam sea and ${\chi}=150^{\circ}$. In the evaluation of passenger comfort due to standard acceleration in vertical and lateral direction, it was 80% in head and bow sea. On the other hand, it was shown to be 15% in follow sea. Accordingly, when the expected wave height in a sea area where a training ship was intended to operate was known, it was possible to predict the routing of ship. And altering her course could reduce the passenger comfort by approximately 50%.

• 한국해안·해양공학회논문집
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• 제27권6호
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• pp.382-390
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• 2015

본 연구에서는 SWASH 모형을 이용하여 계절별 이상파랑에 의한 해운대 해수욕장에서 불규칙파의 파랑 변형 및 해빈류 특성을 분석하였다. 개경계에서 불규칙파는 JONSWAP 스펙트럼을 적용하였다. 입사파 조건은 국립해양조사원에서 제공하는 2014년 파랑관측자료를 바탕으로 계절별 대표파를 선정하였다. SWASH에 의한 계절별 해빈류 계산결과는 현장조사 결과와 비교 검토하였다. 하계의 경우 S 계열의 파랑이 지배적이며 동백섬측에서 미포측으로 연안류가 지배적으로 발생하였고 해운대 해수욕장 중앙부근에서는 이안류가 발생하였다. 동계의 경우 ESE 계열의 파랑이 지배적이며 해운대 해수욕장 중앙부근에서 각각 동백섬측과 미포측으로 향하는 연안류가 발생하였다.

• 대한조선학회논문집
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• 제38권2호
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• pp.1-9
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• 2001

본 논문은 소오스 분포법(Source Distribution Method)을 사용하여 측벽 반사효과를 고려한 수치파수조에서의 방향스펙트럼파의 재현과 규칙파로부터 구해진 조파기의 진폭 전달함수를 적용시켜 부산대학교 예인수조에서 실험적으로 재현한 장파정 불규칙파 및 방향스펙트럼파에 대한 연구결과이다. 수치적 재현의 경우 최적의 조파기 설계를 위하여 파 주기의 변화에 따라 조파판과 수조폭을 변화시켜 방향분포함수의 변화를 고찰하였다. 실험적 재현의 경우 장파정 불규칙파와 방향스펙트럼파에 대해서 수조의 길이방향 변화에 따른 파워 스펙트럼 및 통계적 특성치를 비교하여 그 차이점을 살펴보았다. 방향스펙트럼파의 경우 방향분포함수의 변화도 살펴보았다.

• 대한조선학회논문집
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• 제58권2호
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• pp.112-120
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• 2021

The novel wave generating system of a wave flume has been devised by utilizing the analytic solution of wave board motion in idealized two dimensional space. The arbitrary oscillation motion of submerged wave board segment has been defined by sinusoidal motion of upper and lower end of the wave board. The analytic solution of the wave board motion has been represented by the solution of board motion due to flap motion and swing motion. Arbitrary oscillation of the board could be specified by determining amplitude, frequency, and the phase lag. A novel hybrid wave generator could be operated not only in piston motion but also in flap or swing motion by selection of control parameter. The wave generator has unique motion enhancing ability by appending flap motion or swing motion to piston motion in wave generation. In addition the hybrid wave generator has advantages in generating high quality wave spectrum of irregular wave in simulating real sea condition.

• 한국해안·해양공학회논문집
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• 제29권6호
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• pp.286-304
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• 2017

본 연구에서는 어항 등과 같은 소규모 항에서 적용 가능한 격자블록결속에 의한 신형식의 원형유공케이슨을 제안하고, 이러한 방파제의 수리특성을 수치적으로 검토하였다. 본 연구에서 적용한 수치해석 코드는 최근들어 다양한 분야에서 공학적 문제해결을 위해 그 사용예가 급증하고 있는 공중사용허가서(오픈소스 기반) 라이선스 기반의 OpenFOAM(Open Field Operation and Manipulation)에 조파모듈, 투과층 해석모듈, 및 반사파 제어기능 등을 추가한 OLAFOAM을 적용하였다. 본 연구는 먼저, 1) 규칙파 하 3차원슬리트케이슨 방파제에서 파의 파압변동에 대해 기존의 실험 결과와 비교 검토하고, 2) 불규칙파를 조파하여 목표한 파의 재현과 주파수스펙트럼을 비교 검토하여 OLAFOAM의 타당성을 검증하였다. 이로부터 슬리트케이슨과 유사한 원형유공케이슨이 설치된 일정수심의 3차원수치파동수조에 불규칙파를 조파하여 유수실 폭과 유의파고 및 유의주기의 변화에 따른 원형유공케이슨 방파제에서 월파량, 반사율, 파압분포 및 그들의 상호연관성을 면밀히 검토 분석하였다. 이로부터 파압분포는 불투과연직벽체에 대한 Goda 식의 결과보다 매우 작은 결과를 나타내었으며, 반사율은 기존의 슬리트케이슨에서 반사율의 변동범위 내에 존재하는 것을 알 수 있었다.

• 한국해양공학회지
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• 제19권6호통권67호
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• pp.58-63
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• 2005

The estimation of springing responses for recent ships is carried out, and application to a ship design is described. To this aim, springing effects on hull girder were re-evaluated, including non-linear wave excitations and torsional vibrations of the hull. The Timoshenko beam model was used to calculate stress distribution on the hull girder, using the superposition method. The quadratic strip method was employed to calculate the hydrodynamic forces and moments on the hull. In order to remove the irregular frequencies, we adopted 'rigid lid' on the hull free surface level, and addedasymptotic interpolation along the high frequency range. Several applications were carried out on the following existing ships: The Bishop and Price's container ship, S-175 container ship, large container, VLCC, and ore carrier. One of them is compared with the ship measurement result, while another with that of the model test. The comparison between the analytical solution and the numerical solution for a homogeneous beam-type artificial ship shows good agreement. It is found that Most springing energy comesfrom high frequency waves for the ships having low natural frequency and North Atlantic route etc. Therefore, the high frequency tail of the wave spectrum should be increased by $\omega$$\^{-3}$ instead of $\omega$$\^{-4}$ or $\omega$$\^{-5}$ for the springing calculation.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.173-178
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• 2004

The estimation of springing responses for recent ships are carried out and application to a ship design are described. To this aim, springing effects on hull girder were re-evaluated including non-linear wave excitations and torsional vibrations of the hull. The Timoshenko beam model was used to calculate stress distribution on the hull girder by the superposition method. The strip method was employed to calculate the hydrodynamic forces and moments on the hull. In order to remove the irregular frequencies, we adopted 'rigid lid' on the hull free surface level and added asymptotic interpolation along the high frequency range. Several applications to the existing ships were carried out. They are Bishop and Price's container ship, S-175 container ship, large container, VLCC and ore carrier. One of them is compared with ship measurement result while another with that of model test. Comparison between analytical solution and numerical one for homogeneous beam type artificial ship shows good agreement. It is found that most springing energy came from high frequency waves for the ships having low natural frequency and North Atlantic route etc. Therefore, the high frequency tail of the wave spectrum should be increased by $\omega^{-3}\;instead\;of\;\omega^{-4}\;or\;\omega^{-5}$ for springing calculation.