• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.35-44
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• 2017

Supercavitation is one of the most attractive technologies to achieve high speed for underwater vehicles. However, the multiphase flow with high-speed around the supercavitating vehicle (SCV) is difficult to simulate accurately. In this paper, we use modified the turbulent viscosity formula in the Standard K-Epsilon (SKE) turbulent model to simulate the supercavitating flow. The numerical results of flow over several typical cavitators are in agreement with the experimental data and theoretical prediction. In the last part, a flying SCV was studied by unsteady numerical simulation. The selected computation setup corresponds to an outdoor supercavitating experiment. Only very limited experimental data was recorded due to the difficulties under the circumstance of high-speed underwater condition. However, the numerical simulation recovers the whole scenario, the results are qualitatively reasonable by comparing to the experimental observations. The drag reduction capacity of supercavitation is evaluated by comparing with a moving vehicle launching at the same speed but without supercavitation. The results show that the supercavitation reduces the drag of the vehicle dramatically.

• 한국음향학회지
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• 제39권2호
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• pp.69-76
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• 2020

본 논문은 수중 고속 이동체의 심도 정보를 전송하는 방법을 다룬다. 고속 이동체로부터 전송되는 심도 정보신호는 높은 주파수 변동성을 갖고 수신된다. 제안한 방법에서는 기존의 방법처럼 주파수 동기화뿐만 아니라 시간 축에서 추가로 동기화 하는 방법을 적용하였다. 최대 50 kn로 이동하는 환경에서 수행된 모의실험을 통하여 기존의 방법보다 낮은 해상도를 갖는 도플러 주파수 뱅크를 형성하고, 제안한 방법을 사용하여 심도 정보를 복구한 경우 기존에 6 % ~ 9 %이었던 오류율이 0.2 % ~ 1 %로 낮아진 오류 성능을 나타내었다.

• 로봇학회논문지
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• 제18권1호
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• pp.53-58
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• 2023

In general, in order to operate an autonomous underwater vehicle (AUV) in an underwater environment, a navigation system such as a Doppler Log (DVL) using a Doppler phenomenon of ultrasonic waves is used for speed and direction estimation. However, most of the ultrasonic sensors in underwater is large for long-distance sensing and the cost is very high. In this study, not only canal neuromast on the fish's lateral lines but also superficial neuromast are studied on the simulation to obtain pressure values for each pressure sensor, and the obtained pressure data is supervised using spherical CNN. To this end, through supervised learning using pressure data obtained from a pressure sensor attached to an underwater vehicle, we can estimate the speed and angle of the underwater vehicle in a quasi-static underwater environment and propose a method for a non-ultrasonic based navigation system.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.839-844
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• 1992

There are many specific requirements in the actuation, system for high speed underwater vehicle, such as size, weights, power etc.. In this paper, a high performance compact hydraulic actuation system to satisfy such requirements was designed. The controller of the system was designed using both the conventional PID and VSC which were known to have reliability, robustness respectively. The performance analysis was done for the designed actuation system through computer simulation.

• 로봇학회논문지
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• 제13권2호
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• pp.103-112
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• 2018

In this paper, a high performance underwater vehicle which can be manufactured at low cost is designed and fabricated, and its performance is verified through experiments. To improve efficiency, the Myring equation is used to design the appearance and the duct structure including the thruster is planned to increase the propulsion efficiency while reducing the drag force. Through various methods, it is secured stable waterproof performance, and also is devised to have high speed movement and turning performance. The developed underwater vehicle is equipped with a high output BLDC motor to achieve a linear speed of up to 2 m/s and can change direction rapidly with stability through four rudders. The rudders are driven by coupling a timing belt and a pulley by extending the axis of a servo motor, and are equipped at the end of the body to turn heading. In addition, for stable posture control, the roll keeps its internal center of gravity low and maintains its stability due to restoring force. By controlling the four rudders, pitch and yaw are handled by the PID controller and show stable performance. To investigate the horizontal turning performance, it is confirmed that the yaw rate controller is designed and stable yaw rate control is performed.

• 한국전산유체공학회지
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• 제18권1호
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• pp.49-57
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• 2013

Analysis of fluid-structure interaction for two nearby underwater vehicles immersed in the sea is quite challenging because simulation of flow around them is very difficult due to the complexity of underwater vehicle shapes. The conventional approach using body-fitted or unstructured grids demands much time in dynamic grid generation, and yields slow convergence of solution. Since an analysis of fluid-structure interaction must be based on accurate simulation results, a more efficient way of simulating flow around underwater vehicles, without sacrificing accuracy, is desirable. An immersed boundary method facilitates implementation of complicated underwater-vehicle shapes on a Cartesian grid system. An LES modeling is also incorporated to resolve turbulent eddies. In this paper, we will demonstrate the effectiveness of the immersed boundary method we adopted, by presenting the simulation results on the flow around a modeled high-speed underwater vehicle interacting with a modeled low-speed one.

• 한국추진공학회지
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• 제22권4호
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• pp.12-17
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• 2018

고체 로켓추진기관을 이용한 자연공동형 수중운동체를 수중주행 시험하였다. 수중운동체의 속도 및 주행거리를 측정하고, 수중운동체 표면에 설치한 압력센서로 초공동의 발달에 따른 표면 압력 변화를 조사하였고, 수중카메라로 수중운동체에 초공동이 발생하여 진행하는 과정을 기록하였으며, 이를 이차원 비점성 이론해석법에 근거한 CNU-SuperCT 프로그램을 사용하여 계산한 시뮬레이션 결과와 비교하였다. CNU-SuperCT 프로그램은 수중운동체의 조종면을 포함하지 않고 계산하는 것을 고려하면, 시뮬레이션 결과와 측정결과가 잘 맞는다고 판단되며, 수중촬영결과도 이와 동일한 결과를 보인다.

• 한국군사과학기술학회지
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• 제19권2호
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• pp.227-235
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• 2016

Heavy-weight high speed underwater vehicle(HSUV) is launched from the submerged mother ship. For the safety point of view, it is important to confirm whether the HSUV would touch the launching mother ship. In this paper, the hydrodynamic force and moment were modeled by the polynomials of motion variables and the simple lift and drag acting on a plate and cylinder which consist of the HSUV's several parts. The mother ship was assumed as the Rankine half body to consider the flow field near the moving ship. Such hydrodynamic force and moment were included in the 6 DOF equations of motion of the HSUV and the dynamic simulations for the various conditions of the HSUV until the propeller activation were performed. Developed simulation program is expected to reduce the number of expensive sea trial test to develop safety logic of the HSUV at the initial firing stage.

• 한국해양공학회지
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• 제26권5호
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• pp.81-86
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• 2012

Unmanned underwater vehicles have many applications in scientific, military, and commercial areas because of their autonomy. In many cases, an underwater vehicle adopts a control algorithm based on a tactical inertial sensor for precise control. However, a control algorithm that uses a tactical inertial sensor is unsuitable for some underwater vehicle missions such as torpedo decoys. This paper proposes a control algorithm for an unmanned underwater vehicle that does not require precise control. The control algorithm proposed for an unmanned underwater vehicle adopts a low cost MEMS inertial sensor, and simulations using the specifications of the MEMS inertial sensor under development are performed to verify the control algorithm under a real environment. The results of these simulations are presented.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.188-192
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• 2009

A massive cavity is generated behind the underwater vehicles, such as marine propellers, pump impellers, nozzles, injectors, torpedoes, etc. when a underwater vehicle moves at very high speed in the underwater. At this point it makes supercavitating flow and the nose, ie., the cavitator is very important fator at the vehicle since it should be surrounded by the cavity. The present work has focused on the simulation of cavitation flow using the new cavitator. The governing equation is the Navier-Stokes equation based on homogeneous mixture model. For the code validation, the results from the present solver have been compared with experiments and other numerical results. A fairly good agreement with the experimental data and other numerical results have been obtained.