• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.2
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• pp.146-154
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• 2009

Dynamic response of a hull mounted sonar(HMS) to shocks transmitted through hull structures is analyzed and then the structural reliability of the sonars is evaluated. Finite element model of the hull mounted sonar is established and the transient responses to the shock is calculated using MSC.NASTRAN. According to BV043, the maximum allowable accelerations at the foundation of the sonar are converted from the shock spectra allowable for HMS. They are applied vertically and horizontally, respectively, using the large mass method. The structural reliability is evaluated by comparing the von-Mises stresses with the material yield stress. The drum for sensors shows a high reliability owing to mounts by which the shock waves from the base structure are well protected. However, the mounts between the base structure and the drum to mount sensors show a high stress intensity. The base structure also reveals a high stress intensity at the connection points to the hull.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.193-199
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• 2019

In this paper, the results of underwater vibration experiment are analyzed to verify platform vibration-induced noise isolation characteristics of a hull-mounted acoustic sensor. The experimental condition causing platform vibration-induced noise is generated using the mock-up hull, where the acoustic sensor is installed, with shaker in an acoustic water tank. The performance indices of ATF (Acceleration Transfer Function), AVS (Acceleration Voltage Sensitivity), and IL (Insertion Loss) for the acoustic sensor are calculated from the output of the standard accelerometers, which are installed on the mock-up hull and the acoustic sensor, and the output signal of the acoustic sensor. The frequency-dependent noise isolation characteristics of the acoustic sensor are analyzed based on the calculated performance indices and an effectiveness of the experiment is examined.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.20-20
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• 1998

적 잠수함을 탐지했을 때 적 잠수함이 10km 이내의 거리에서는 어뢰에 부착된 선체 부착형 능동소나로 적 잠수함을 추적하여 직접 공격하는 방법이 효과적이다. 그러나 10km에서 19km 정도의 거리인 경우에는 로켓트를 이용하여 어뢰를 목표지점까지 운반하고 운반된 어뢰가 바닷속에 착수하면 수동예인 음탕기(TASS)로 적 잠수함을 탐지 추적하는 체계가 효율적이다. 19km 이상이 되면 헬기로 적 잠수함을 탐지하고 목표지점에 어뢰를 투하시키는 방안이 일반적으로 운용되고 있다. 그러나 최근에는 50km 정도까지도 유도탄으로 어뢰를 운반하는 체계가 선호되어 적용되고 있기도 하다.

• The Journal of the Acoustical Society of Korea
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• v.43 no.2
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• pp.145-151
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• 2024

Recently, ship hull-mounted passive sonar system solution is needed in the perspective of improving target detection and elimination of vibration-induced noise. Our research team suggests acousticvibration matching method using front and rear signal of a sensor as the improvement of the problem above. Thus in this paper, theoretical background about matching method and its application on finite element method based multi-physics simulation are described. Furthermore, it is shown that target detection and hull vibration performance are improved by using matching method under the condition of our sensor system. Finally, practicality and future research are discussed.

• The Journal of the Acoustical Society of Korea
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• v.39 no.6
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• pp.541-548
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• 2020

To overcome the disadvantage of hull mounted sonar, many countries operate dipping sonar system for helicopter. Although limited in performance, this system has the advantage of ensuring the survivability of the surface ship and improving the detection performance by adjusting the depth according to the ocean environment. In this paper, a method to calculate the optimal depth of the dipping sonar for helicopters is proposed by applying an optimization algorithm. In addition, in order to evaluate the performance of the sonar, the Sonar Performance Function (SPF) is defined to consider the ocean environment, the depth of the target and the depth of the dipping sonar. In order to reduce the calculation time, the optimal depth is calculated by applying Simulated Annealing (SA), one of the optimization algorithms. For the verification of accuracy, the optimal depth calculated by applying the optimization technique is compared with the calculation of the SPF. This paper also provides the results of calculation of optimal depth for ocean environment in the East sea.

• Journal of Navigation and Port Research
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• v.38 no.4
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• pp.335-341
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• 2014

Faced with global agenda of greenhouse abatement program including regulations and $CO_2$ emission trading scheme, shipping companies are enforced to a high level of efficiency in fuel consumption. Accordingly shipbuilding companies worldwide are required to develop fuel-efficient ships which otherwise traditionally consume a great amount of fossil fuels. In this dissertation, relevant to the improvement of fuel efficiency for commercial ships, design methodology through the numerical simulations are intensively described. This work consists of derivation of effective hydrodynamic design practice based on the application of longitudinal grooves to effectively improve the pressure distribution around ship hull. The primary objective of the present study is to improve ship resistance performance using longitudinal grooves which originate from long strips on the abdomen of humpback whale. Several groove shapes have been extensively investigated and the proposed shape efficiently controlled the variation of pressure distributions acting on the hull surface.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.11
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• pp.2569-2574
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• 2012

HMS(Hull Mount Sonar) equipment mounted on PCC(Patrol Combat Corvette) is suitably designed for active mode, and the specific character of sensor or system is not appropriate for the frequency range to detect a torpedo. In this article, in order to implement the function of detecting torpedoes with HMS of existing PCC, I will analyze the feature of input signals each PCCs and design a circuit to compensate reversely for the input signal in certain frequency. And also, I will suggest the most adequate torpedo defense system suitable for the special operating environment and the characteristic of naval vessels, implementing functions such as AGC of input signal and fixing the frequency range of different input signals per different warships.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.576-582
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• 2016

To cope with international regulations, such as Energy Efficiency Design Index (EEDI), Ship Energy Efficiency Management Plan (SEEMP) and so forth, and to enforce limitations on $CO_2$ emissions, green-ship technology to lower fuel consumption has been actively researched, and the development of an energy-saving device (ESD) is being pursued. In order to design an ESD for small and medium-sized domestic vessels, an analysis on flow characteristics has been performed in the present study. Through a model test and numerical analyses, the characteristics of flow around the stern bilge and bulb have been compared to improve wake quality and resistance performance. As a result of these comparisons and analyses, a vertical plate has been adopted,, as a new ESD. Design criteria for the proposed ESD are also suggested. By applying this new ESD, it is expected that the total resistance and average nominal wake can be reduced by 3.04 % and 18.8 %, respectively.