• Journal of Ship and Ocean Technology
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• 제6권2호
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• pp.12-22
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• 2002

Offshore pipelines play an important role in the transportation of gas, oil, water and oil products. It is common to have a group of pipelines in the oil and gas field. To reduce the installation cost and time, dual pipelines are designed. There are great advantages in the installation of dual pipelines over two separate single lines. It can greatly reduce the cost for trench, back-filling and installation. However the installation of dual pipelines often requires technical challenges. Pipelines should be placed to be stable against external loadings during installation and design life period. Dual pipelines in trench can reduce the influence of external forces. To investigate the flow patterns and forces as trench depth and slope changes, number of experiments are conducted with PIV(Particle Image Velocimetry) equipment in a Circulating Water Channel. Numerical approaches to simulate experimental conditions are also made to compare with experimental results. The velocity fields around dual pipelines in trench are investigated and analysed. Comparison of both results show similar patterns of flow around pipelines. It is proved that the trench depth contributes significantly on hydrodynamic stability. The trench slope also affects the pipeline stability. The results can be applied in the stability design of dual pipelines in trench section. The complex flow patterns can be effectively linked in the understanding of fluid motions around multi-circular bodies in trench.

• 한국항해항만학회지
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• 제35권3호
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• pp.197-204
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• 2011

회류수조에서의 대각도 정적(static) 모형실험을 통해 Manta형 무인잠수체에 작용하는 동유체력을 측정하였으며, 동유체력에 미치는 Reynolds수의 영향을 고찰하였다. 이를 위해 동유체력을 cross-flow drag과 양력(lift force)으로 성분 분석을 하였으며, 양력 성분에는 Reynolds수의 영향을 무시하고, cross-flow drag 성분에만 Reynolds수의 영향을 고려하였다. 그 후 이들 두 성분을 다시 합성함으로써 실물 무인잠수정에 작용하는 동유체력의 추정 기법을 제시하였다.

• 수산해양기술연구
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• 제51권3호
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• pp.312-320
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• 2015

The 1/5 scale-down model of the Bycatch Reduction Device (BRD) from an Argentinean demersal trawl was tested in a circulating water channel. The BRD is designed to help small Hake (merluza, merluccius hubbsi) to escape from a trawl. It is settled in front of a trawl codend, and is equipped with selection grids that help small fish to escape from the gear and guiding panels that help fish to meet with the grids. Bars of the grids are wires covered by the PVC and other parts of the BRD are made of net. When the velocity was less than 0.65 m/sec (2.81 Kont when translated to real towing speed) which is slow speed compared with real towing speed, position between an upper guiding panel and an upper selection grid were good to help small fish to escape. When the velocity was more than 0.8 m/sec (3.41 Knot when translated to real towing speed) which is similar to and faster than real towing speed, it was considered that small fish may have difficulties in escaping because the gap was not enough between an upper guiding panel and an upper selection grid. The lower selection grid was sat on the bottom of the tank without an angle due to the weight that it carries. Improvements were proposed to position the panels and the grids better.

• 해양환경안전학회지
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• 제23권2호
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• pp.200-207
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• 2017

선박에서 제어판을 가지는 목적은 선박의 운동을 제어하는데 있다. 제어판은 단동타의 형태일수도 있고 고정된 부분과 이동하는 부분의 조합에 의해 구성될 수도 있다. 이러한 제어판은 그 고유의 목적에 맞도록 역할을 수행하는 기능을 가지며, 유체와 상대적인 운동과 원초적인 기능에 의해 조정력을 증가시키는 것이다. 이러한 힘과 모멘트는 영각의 변화와 회전에 의해서 생성되고 선박의 조종성능을 결정한다. 본 논문에서는 플랩러더와 물분사러더의 2차원 유동특성을 회류수조에서 PIV기법을 이용하여 각각 계측하였다. 모델시험은 플랩러더와 물분사러더를 NACA0012의 영각과 플랩각을 변화시키면서 수행하였다. 2프레임 입자추적기법은 유동장에서 속도분포를 득하는데 이용되었다. 전체실험에서 레이놀즈수 $Re{\fallingdotseq}3.0{\times}10^4$를 적용하였으며 상호비교를 통해 계측된 결과값을 비교평가하였다.

• 한국항해항만학회지
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• 제34권5호
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• pp.331-336
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• 2010

원형실린더가 균일한 유입유동에서 자유수면 으로부터 깊이를 달리했을 경우 박리점, 경계층 및 칼만 와열의 주기 등의 변화로 인하여 시스템 전체 에너지에 변화를 초래한다. 본 연구에서는 원형실린더의 침수 깊이를 변화시키며 $Re=1.0{\times}10^3$에서 유동장을 계측하였다. 2차원 그레이 레벨 상호상관 PIV기법을 이용하여 원형실린더 주위의 유동특성을 알아보기 위하여 상호 비교하는 방법을 적용하였다. 자유수면의 점성과 마찰에 의해 발생하는 원형실린더 주변유동은 경계층을 변화시키고 후류유동에 교란을 일으킨다. 특히, 몰수체의 깊이가 d=1.0D의 경우에 있어서 경계층의 변화가 후류로 길게 형성되었다. 원형실린더의 깊이가 d=1.5D에서부터 자유수면의 영향이 감소하고 칼만 와열이 발달하였다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.79-84
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• 2004

Initial hull form of 10 G/T and 40 knots class coastal patrol boat is newly developed. The resistance performances are experimentally and numerically investigated by model test at high speed circulating water channel(CWC) and CFD technique. The effect of a fin attached at hull side and initial trim are studied together. Wave patterns are observed to make clear the relation between the resistance performance and the wave characteristics. it can be found that the initial trim plays a role to increase the resistance performance above a certain velocity.

• 대한조선학회논문집
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• 제37권3호
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• pp.37-44
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• 2000

수면 하에서 정속으로 움직이는 MACA0012 수중익에 의하여 생성되는 정상파 및 쇄파에 대한 실험적 연구를 회류수조에서 수행하였다. 실린더의 몰수깊이에 따른 자유표면 파형을 관측하였고, PIV를 이용하여 수중익과 자유표면 사이 유동장의 순간속도와 평균속도를 계측한 후 와도분포를 구하였다. 쇄파의 발생, 전개 그리고 소멸과정을 조사하였고, 특히 자유표면 부근의 와류 구조와 같은 복잡 순간유동장의 가시화를 통하여 수중익과 쇄파 간의 상호작용을 해석하고자 하였다. 본 실험으로 PIV 계측기법은 조선해양공학의 다양한 연구분야에 훌륭히 적용될 수 있음을 보았고 더욱이 정량적인 해석이 필요한 실험에도 사용이 가능함을 확인하였다.

• 한국어업기술학회:학술대회논문집
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• 한국어업기술학회 2005년도 춘계 학술대회 논문집
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• pp.62-69
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• 2005

Maneuverability of ships has been receiving a great deal of attention both concerning navigation safety and the prediction of ship maneuvering characteristics, to improve it. High-lift device could be applied to design of rudder at design stage. Now, we carried out the flow visualization and inversitgation of flow around a flap rudder (trailing-edge flap). Flow visualization results of flap defection shown as the flow around a NACA0020 Flap Rudder will be conducted in a Circulating Water Channel. The purpose of this investigation will be to investigate the development of the separation region on the flap rudder with the variation of angle of attack and determine the angle of attack at which the flow separates and reattaches.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.190-195
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• 2001

Flow patterns are very complex and interactive between cylinders. The patterns are turbulent and non-linear caused by various factors. In this paper, flow patterns and pressure gradient around vertical cylinders were investigated by experiment. Changing gaps between cylinders the flow patterns are measured at a fixed coming velocity. Flow patterns showed very complex and closely related to the coming velocity and cylinder space. The pressure gradient around the flow field is observed by twelve hole pitot tubes and manometer. The experiment has been conducted in circulating water channel with PIV system. That can visualize flow patterns. The laser beam was used to reflect the image from particles and recorded by CCD camera. The cylinders were spaced from ID to 5D with 0.5m/sec of incoming flow velocity. The experimental results using pitot tube showed in good agreement with results of precious by others study. The results can be applied in the understanding and design of multiple pile array structures.

• 한국유체기계학회 논문집
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• 제16권5호
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• pp.24-28
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• 2013

Visualization of internal flow of a regenerative blower has been made by injecting a tracer directly into the flow. For the convenience of visualization, working fluid has been replaced by water and marbling color oil has been used as a tracer. Oil droplet has been injected near the inlet of the blower and the streak has been recorded using a high speed camera with the illumination of high power light sources. At first, droplets have irregular motion in the near inlet area and enter into a groove of the impeller. Then the droplets circulate inside the groove while translated by the rotational motion of the impeller. When the droplets get out of the impeller groove, their speed is lower than that of impeller. And the droplets repeatedly enter into the groove and circulate inside the grooves. Then the droplets either flow to the outlet or reenter into the inlet area through stripper. Through this experimental study, internally circulating motion of the flow inside a regenerative blower has been characterized.