• Title/Summary/Keyword: 수중예인체

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Absolute Sonar Position on Side Scan Sonar Data Processing (Side Scan Sonar 자료처리에서 수중예인체의 절대위치)

  • Lee, Yong-Kuk;Park, Gun-Tae;Suk, Bong-Chool;Jung, Baek-Hun;Kim, Seong-Ryul
    • Journal of the Korean earth science society
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    • v.24 no.5
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    • pp.467-476
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    • 2003
  • For the seafloor acoustic image mapping of side scan sonar, the beginning step of the procedure is to fix the absolute sonar (tow-fish) position since the sonar is not hull mounted but towed astern. The technical algorithm used to calculate the actual sonar position without any other additional sub-system, i.e., the underwater acoustic position tracking system or the sonar attitude measuring device, was proposed. In the seafloor image mosaic mapping results using the sonar track (not ship track) developed in this study, any ambiguity or inconsistency of seafloor features was not found. The incidental effect from the sonar position determination procedure orients the towing direction of sonar to be smooth, consequently the swath pattern on the across-track direction becomes stable and the blanking phenomenon of the insonification area is reduced conspicuously. This technical method is considered to be an useful tool when applied toother underwater towing vehicle surveys.

A Three-Dimensional Dynamic Analysis of Towed Systems Part 1. A Mathematical Formulation (수중예인시스템의 3차원 동역학 해석 1부: 수학모델 정식화)

  • Hong, Sub;Hong, Seuk-Won
    • Journal of Ocean Engineering and Technology
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    • v.8 no.1
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    • pp.16-22
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    • 1994
  • 수중 예인시스템의 동적 거동 해석을 위한 3차원 비선형 수학모델이 제시되었다. 수중 예인체는 세장보로 이상화되었으며, 보요소의 굽임강성 및 비틈강성의 영향이 수학모델에 포함되었다. 축류가 지배적인 비정상 상대유동장내의 세장예인체의 횡방향 운동에 따른 유체동역학적 반력과 기진력에 관한 비선형 3차원 수학 정식화가 수행되었다.

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3D Nonlinear Fully Coupled Simulation of Cable and Tow-fish System (케이블-수중 예인체 시스템의 3차원 비선형 완전 연성해석)

  • Go, Gwangsoo;Lee, Euntaek;Ahn, Hyung Taek
    • Journal of Ocean Engineering and Technology
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    • v.30 no.6
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    • pp.458-467
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    • 2016
  • In this paper, a strongly coupled method for investigating the interaction between a cable and tow-fish is presented. The nodal position finite element method was utilized to analyze the nonlinear cable dynamics, and 6DOF equations of motion were employed to describe the 3D rigid body motion of the tow-fish. Combining cable and tow-fish systems into a single formulation allowed the two nonlinear systems to be strongly coupled into a unified nonlinear system. This strongly coupled system was numerically integrated in the time domain using a predictor/multi-corrector Newmark algorithm. To demonstrate the validity, efficacy, and applicability of the current approach, two different scenarios (virtual and sea trial) were simulated, and the simulation results were validated using the physical plausibility and the sea trial test.

Estimation of Maneuverability of Underwater Vehicles with Ahead Propeller by the Vertical Planar Motion Mechanism Test (VPMM 시험을 통한 선수부에 프로펠러를 갖는 수중운동체의 조종성능 추정)

  • Shin, Myung-Sub;Kim, Dong-Hwi;Kim, Yagin;Hwang, Jong-Hyon;Baek, Hyung-Min;Kim, Sung-Jae;Park, Sang-Jun;Choi, Young-Myung;Park, Hongrae;Kim, Eun-Soo
    • Journal of Navigation and Port Research
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    • v.46 no.3
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    • pp.168-178
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    • 2022
  • In this study, the resistance test, the vertical static angle of the attack test and VPMM test will be conducted to estimate the maneuverability of underwater vehicles with ahead propeller. The vertical static test will be conducted within the range of -40deg to 40deg, to investigate the cross-flow drag at high incidence angles. The tests will be conducted by dividing the propeller rotation into a case in which the propeller rotates at a specific rpm, and a case in which the propeller rotates naturally, according to the towing speed. Hydrodynamic coefficients of vertical direction will be estimated by the captive model tests. Additionally, the vertical dynamic stability index based on estimated hydrodynamic coefficients will be calculated and the impact of the propeller revolution state on the index will be investigated. The results are expected to be used as reference test data for underwater vehicles with ahead propeller.

Simulation-Based Determination of Hydrodynamic Derivatives and 6DOF Motion Analysis for Underwater Vehicle (시뮬레이션 기반 수중 운동체의 유체력 미계수 결정 및 6자유도 운동해석)

  • Go, Gwangsoo;Ahn, Hyung Taek;Ahn, Jin-Hyeong
    • Journal of Ocean Engineering and Technology
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    • v.31 no.5
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    • pp.371-377
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    • 2017
  • This paper introduces a simulation-based determination method for hydrodynamic derivatives and 6DOF (degrees-offreedom) motion analysis for an underwater vehicle. Hydrodynamic derivatives were derived from second-order modulus expansion and composed of the added mass, and linear and nonlinear damping coefficients. The added mass coefficients were analytically obtained using the potential theory. All of the linear and nonlinear damping coefficients were determined using CFD simulation, which were performed for various cases based on the actual operating condition. Then, the linear and nonlinear damping coefficients were determined by fitting the CFD results, which referred to 6DOF forces and moments acting on an underwater vehicle, with the least square method. To demonstrate the applicability of the current study, 6DOF simulations for three different scenarios (L-, U-, and S-turn) were carried out, and the results were validated on the basis of physical plausibility.

6DOF Simulation and Determination of Hydrodynamic Derivatives of Underwater Tow-Fish Using CFD (CFD를 이용한 수중 예인체의 유체력 미계수 결정과 6자유도 운동해석)

  • Go, Gwangsoo;Lee, Euntaek;Ahn, Hyung Taek;Kim, Seongil;Chun, Seung Yong;Kim, Jung Suk;Lee, Byeong Hee
    • Journal of the Society of Naval Architects of Korea
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    • v.53 no.4
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    • pp.315-328
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    • 2016
  • Techniques for determinating hydrodynamic derivatives of underwater tow-fish using CFD(Computational Fluid Dynamics) are described in this paper. Main components of hydrodynamic derivatives are added mass, linear damping and non-linear damping coefficients. In this study, linear and non-linear damping coefficients for translational velocities are settled by CFD analysis. In order to analyze the underwater tow-fish, UlsanFOAM based on open-source CFD code, namely OpenFOAM, is employed. By simulating pitch and yaw angle variation of underwater tow-fish, 6DOF(Degree-of-Freedom) forces and moments are estimated at each attitudes. In order to determinate the hydrodynamic derivatives, curves(forces and moments vs attitude) for CFD results are fitted by least square methods. To demonstrate the applicability of the current approach, two different problems(impulsive side towing and straight towing) are simulated and all results are validated.

A correction of synthetic aperture sonar image using the redundant phase center technique and phase gradient autofocus (Redundant phase center 기법과 phase gradient autofocus를 이용한 합성개구소나 영상 보정)

  • Ryue, Jungsoo;Baik, Kyungmin
    • The Journal of the Acoustical Society of Korea
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    • v.40 no.6
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    • pp.546-554
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    • 2021
  • In the signal processing of synthetic aperture sonar, it is subject that the platform in which the sensor array is installed moves along the straight line path. In practical operation in underwater, however, the sensor platform will have trajectory disturbances, diverting from the line path. It causes phase errors in measured signals and then produces deteriorated SAS images. In this study, in order to develop towed SAS, as tools to remove the phase errors associated with the trajectory disturbances of the towfish, motion compensation technique using Redundant Phase Center (RPC) and also Phase Gradient Autofocus (PGA) method is investigated. The performances of these two approaches are examined by means of a simulation for SAS system having a sway disturbance.

Design and Experimental Study of a Launch and Recovery System for an Underwater Tow-fish with Consideration of Sea State (해상상태를 고려한 수중예인체 진회수시스템 설계 및 실험)

  • Kang, Jin-il;Sur, Joo-no;Jeong, Seong-hoon;Choi, Hyeung-sik;Kim, Joon-young;Kim, Myung-gyung;Kim, Jung-hoon
    • Journal of Advanced Navigation Technology
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    • v.21 no.4
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    • pp.332-338
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    • 2017
  • Launch and recovery system(LARS) is required to perform an USV-based underwater exploration. Through the analysis of the requirements according to the scenario of underwater exploration, the mechanism of LARS and the conceptual design of the mechanical parts of LARS are carried out. In addition, a USV motion can be induced due to environmental disturbances such as waves, so the detailed design of LARS for recovering the underwater tow-fish stably in consideration of the USV motion is performed. To verify the performance of launch and recovery operations, LARS and test bed were developed. The results show that the proposed LARS can stably launch and recovery an underwater tow-fish.