• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.141-146
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• 2005

This paper an application example of PIV system for analyzing the flow of submerged structure. In this paper, we introduce an analysis method to predict the characteristics of flow around the neighboring fields of tetrapod and fishing reef in order to develop a high performance model. Flowing phenomenon according to velocity distribution and flow separation around the submersed body were obtained by PIV system. Flow visualization has conducted in a circulating water channel by a high speed camera and etc.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.06a
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• pp.5-6
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• 2009

The influence of different appendage shape on the characteristics of hydrodynamic forces on Manta-Type Unmanned Undersea Test Vehicle(MUUTV) was discussed experimentally. Fuselage only MUUTV model and two types of MUUTV model with different appendage geometries were considered as subject of discussion Oblique tow experiment was carried out in circulating water channel with three MUUTV models. A point of difference in hydrodynamic force characteristics among three models was compared and discussed. Furthermore, the linear hydrodynamic derivatives obtained from model experiment were compared with theoretical calculation results from slender body theory, added mass theory and ete. Based on the hydrodynamic force characteristics, motion stability of two types of MUUTV model with different appendage geometries was discussed and compared each other. Through the above analysis, the more suitable shape of appendage geometry was made clear.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.105-108
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• 2002

Highly swept leading edge extension(LEX) applied to delta wings has greatly improved the subsonic maneuverability of contemporary fighters. In this study, systematic approach by PIV experimental method within a circulating water channel was adopted to study the fundamental characteristics of induced vortex generation, development and its breakdown appearing on a delta wing model with or without LEX in terms of four angles of attack$(15^{\circ},\;20^{\circ},\;25^{\circ},\;30^{\circ})$ and six measuring sections$(30\%,\;40\%,\;50\%,\;60\%,\;70\%,\;80\%)$ of chord length. Distributions of time-averaged velocity vectors and vorticities over the delta wing model were compared along the chord length direction. High-speed CCD camera which made it possible to acquire serial images is able to get the detailed information about the flow characteristics occurred on the delta wing. Especially quantitative comparison of the maximum vorticity featuring the induced pressure distribution were also conducted to clarity the significance of the LEX existence.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.32-42
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• 2006

This study aims at establishing a technique for sailing yachts model tests with sailing condition. It is very important to estimate a ship's potential speed performance before building a real ship. Several methods are used to estimate a ship's potential speed performance such as using parent ship data, standard vessel chart and model test. Model test is the most precise among these options. In korea. model testing is widely used with general vessels but not with sailing yachts. Because sailing yachts are propelled with heeling and leeway. using the wind. another method is needed to estimate their speed. The new model test. which is different from tests for upright general vessels, is in a great demand. In this paper. we describe a test method for the sailing yacht model test. based on Masuyama's equation of motion. And we describe choosing scale ratio. production process and materials of the model. Also. various ways of measuring instruments. attaching jigs and adjusting calibration are described so that they can be utilized as useful data for model testing.

• Journal of the Korea Safety Management & Science
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• v.19 no.4
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• pp.301-307
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• 2017

The planing hull is characterized by a large change in the posture according to the speed, and the shape of the propeller varies, so that the hull resistance varies greatly depending on the propeller used. Especially, the Savitsky system, which is widely used for estimating the resistance of planing hull, does not consider the characteristics of these propeller and ship bottom spray rails. In this paper, in order to investigate the difference in resistance characteristics between the propeller and the bottom of the propeller of 6m and 12m class propeller using propeller such as outboard or stern drive, A comparative test was conducted on resistance and attitude posture changes in the Circulating Water Channel of Institute of Medium & Small Shipbuilding. As a result of comparison test, it was confirmed that there is a clear difference in the attitude change due to the presence of the bottom floor spray rail and the change in resistance characteristics due to the installation of the propeller. However, attitude change with the propeller was found to be insignificant.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1161-1168
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• 2005

A Multi-Sectional 3D-PTV algorithm was developed to reduce the calculation time of the conventional GA-3D-PTV. The hardware system of the constructed 3D-PTV system consists of two high-speed cameras ($1,024\times1,018$ pixels, 60 fps), a metal halogen lamp (400W) and a host computer. The sphere(D=30mm) is suspended in a circulating water channel $(300mm\times300mm\times1,200m)$ and Reynolds number is 1,130. About 5,000 instantaneous three-dimensional velocity vectors have been obtained by the constructed 3D-PTV system. Turbulent properties such as turbulent intensity, Reynolds stress and turbulent kinetic energy were obtained. An eigenvalue analysis was carried out using the obtained instantaneous 3D velocity vectors to get the topological relations of the asymptotically stable critical point. Two structured shells, inner shell and outer shell, were found in the sphere wake and their motions were clarified by the measured data.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1599-1603
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• 2008

발전소 냉각수 배수로에는 유속 2 m/s 이상의 빠른 흐름의 수로가 존재하여 수력발전을 꾀할 수 있어, 하동화력의 경우 조류발전 수차인 헬리컬 수차를 이용한 수력 개발이 진행 중이다. 하동화력 배수로는 약 630 m의 암거와 약 250 m의 개수로로 이루어져 있는데, 현재 상업용 발전설비 개발을 위해 시험용 수차발전 설비를 개수로로 이어지는 암거 출구부에 설치하여 성능 시험을 추진하고 있다. 이에 본 연구에서는 발전 설비의 설치로 인한 수위 증가가 냉각수 순환 계통에 미치는 영향을 파악하기 위하여 배수로 구간의 수위변화 또는 압력변화를 수치해석을 통해 분석하였다. 배수로 암거 출구부에 가로 3.6 m ${\times}$ 세로 1.5 m 헬리컬 수차 1 set를 설치하는 경우 저조시에는 seal well 후단(하류측)의 수위가 seal well의 위어 정부표고를 넘지 않아 수차구조물에 의한 압력변화가 상류로 미치는 영향이 없었다. 그러나 고조시에는 seal well 전 후단이 만관 관수로 흐름이 되어 하류의 압력변화가 상류로 전파되었다. 단, 수차구조물을 설치한 경우 순환수 펌프를 처음 기동할 때 압력파의 전파로 인해 초기 약 10 분간 불안정한 압력변화가 발생하나 수차구조물 설치 전인 현상태에서 발생하는 압력변화 범위를 벗어나지는 않고 이내 안정되며, 수차구조물 설치로 인한 수위 증가분만큼의 펌프 양정고 증가로 소요 동력이 증가할 수 있으나 0.2 m 내외의 미약한 증가이므로 정상 운전에는 문제가 없을 것으로 판단되었다. 따라서 수차구조물 설치 시, 저조시에는 순환수계통에 영향을 주지 않으며, 고조시에도 일부 시간 동안 미약한 수두변화만 있을 뿐 순환수 계통의 안전에는 지장을 주지 않을 것으로 확인되었다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.21-27
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• 2008

Triangular structure is used as basic shape of artificial structures for generating the upwelling current in order to make rich fishing ground at sea. Artificial upwelling current could bring the deep sea water containing a lot of nutrients from the bottom up to the surface. The purpose of this study is to examine the flow characteristics around underwater triangular structure with various stratification parameter. An experimental study was carried out for the triangular structure model in the circulating water channel to investigate flow characteristics by flow visualization method. A velocity fields around the underwater structure were measured by particle image velocimetry(PIV). The experimental results showed that the upwelling effect at the back and upper region of the structure could be best when the water depth was 2 times of the structure height and the stratification parameter was approximately 3.0. These quantitative data will be useful to determine the functional efficiency cf artificial upwelling structures.

• Journal of Ocean Engineering and Technology
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• v.35 no.6
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• pp.434-445
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• 2021

This paper proposes an optimal design method for an unmanned underwater vehicle (UUV) platform to overcome strong current. First, to minimize the hydrodynamic drag components in water, the vehicle is designed to have a streamlined disc shape, which help maintaining horizontal motion (zero roll and pitch angles posture) while overcoming external current. To this end, four vertical thrusters are symmetrically mounted outside of the platform to stabilize the vehicle's horizontal motion. In the horizontal plane, four horizontal thrusters are symmetrically mounted outside of the disc, and each of them has the same forward and reverse thrust performances. With these four thrusters, a specific thrust vector control (TVC) method is proposed, and for external current in any direction, four horizontal thrusters are controlled to generate a vectored thrust force to encounter the current while minimizing the vehicle's rotation and maintaining its heading. However, for the numerical simulations, the vehicle's hydrodynamic coefficients related to the horizontal plane are derived based on both theoretical and empirically derived formulas. In addition to the simulation, experimental studies in both the water tank and circulating water channel are performed to verify the vehicle's various final performances, including its ability to overcome strong current.

• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.37-41
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• 2012

Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very strong current on the west coast, with a tidal range of up to 10 m, there are many suitable sites for the application of TCP (tidal current power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential component that can convert tidal current energy into rotational energy to generate electricity. The design optimization of a rotor is very important to maximize the power production. The performance of a rotor can be determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical axis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advantage to a caisson-type breakwater because it allows water to circulate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance analysis was carried out using CFD. A physical model was also demonstrated in CWC, and the results are compared with CFD.