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백부근,김기섭,김경열,편영식,김준형,정철민,김찬기 한국해양환경·에너지학회 2012 한국해양환경·에너지학회 학술대회논문집 Vol.2012 No.5
초음파 나노 표면 개질법에 의해 마이크로 딤플 패턴을 금속 물체 표면에 생성시킬 수 있는데, 이 딤플 패턴에 의한 항력 성능을 살펴 보기 위하여 딤플 표면 처리한 평판에 대한 힘력 감소 연구를 수행하였다. 딤플 표면에 의하여 난류 경계층 내에서 주유동 방향의 모멘텀이 증가하였으나 난류 강도 값에는 큰 변화가 없었다. 주유동에 대한 항력 측정은 후류 유속 측정결과를 이용하여 단면(profile) 저항을 계산하였고 6분력계를 이용하여 평판에 영향을 주는 항력을 직접 계측하였다. 후류의 유동장은 입자영상속도계(particle image velocimetry)를 이용하여 계측하였다. 딤플 처리된 평판에서 항력 감소율은 최대 4.6%의 값을 보였으며 10<SUP>6</SUP>~10<SUP>7</SUP> 정도의 레이놀즈 수 영역대에서 그 수가 증가하여도 항력이 지속적으로 증가하는 경향을 보였다.
5.5MW급 아지무스 추진기(azimuth thruster)에 대한 대형 캐비테이션 터널 모형시험
백부근,박영하,김기섭,김주인,나윤철,Paik, Bu-Geun,Park, Young-Ha,Kim, Ki-Sup,Kim, Ju-In,Na, Yun-Cheol 대한조선학회 2015 大韓造船學會 論文集 Vol.52 No.1
The development of an azimuth thruster which has the function of dynamic positioning and propulsion has been greatly required as the demand of vehicles with it increases. To develop or design a reliable azimuth thruster, it is appropriate that the performance and cavitation observation tests should be conducted in the regime of high Reynolds number. In the present study, to satisfy high Reynolds number condition new dynamometer for a large azimuth thruster is manufactured and arranged in the test section of the Large Cavitation Tunnel (LCT). The test method composed of the open water and the cavitation observation tests is established successfully in LCT, considering the thruster design.
Development of real-time monitoring system using wired and wireless networks in a full-scale ship
백부근,조성락,박범진,이동곤,배병덕 대한조선학회 2010 International Journal of Naval Architecture and Oc Vol.2 No.3
In the present study, the real-time monitoring system is developed based on the wireless sensor network (WSN) and power line communication (PLC) employed in the 3,000-ton-class training ship. The WSN consists of sensor nodes, router, gateway and middleware. The PLC is composed of power lines, modems, Ethernet gateway and phase-coupler. The basic tests show that the ship has rather good environments for the wired and wireless communications. The developed real-time monitoring system is applied to recognize the thermal environments of main-engine room and one cabin in the ship. The main-engine room has lots of heat sources and needs careful monitoring to satisfy safe operation condition or detect any human errors beforehand. The monitoring is performed in two regions near the turbocharger and cascade tank, considered as heat sources. The cabin on the second deck is selected to monitor the thermal environments because it is close to the heat source of main engine. The monitoring results of the cabin show the thermal environment is varied by the human activity. The real-time monitoring for the thermal environment would be useful for the planning of the ventilation strategy based on the traces of the human activity against inconvenient thermal environments as well as the recognizing the temperature itself in each cabin.
백부근,박일룡,김기섭,이건철,김민재,김경열 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.9
The main objective of the present study is to design a bubble collecting section for use in ventilated supercavitation experiments. The large amounts of air ventilated around a cavitator split into small bubbles that follow the water’s passage through the water tunnel. The presence of these bubbles in the test section of the water tunnel prevents effective observation of supercavitation. To enable the clear observation of cavitation shape, a bubble collecting section with large volume is necessary upstream of the test section to collect bubbles. The buoyancy of bubbles provides a simple means for their collection. However, the bubbly flows in such systems have rather high velocities and a non-uniform velocity distribution, which degrades the buoyancy effect. In the present study, a bubble collecting section with three porous plates that produce a uniformly low velocity distribution is designed and analyzed with numerical methods. The effectiveness of this approach is assessed experimentally with the 1/10 miniature model. The reduction of the void fraction downstream of the bubble collecting section was also assessed in the test section. The bubble collecting section in the full-scale water tunnel was also eventually found to be well designed through flow speed measurements and bubble visualization in the test section.
백부근,김기섭,김경열,편영식,김준형,정철민,김찬기 대한조선학회 2012 대한조선학회 학술대회자료집 Vol.2012 No.5
초음파 나노 표면 개질법에 의해 마이크로 딤플 패턴을 금속 물체 표면에 생성시킬 수 있는데, 이 딤플 패턴에 의한 항력 성능을 살펴 보기 위하여 딤플 표면 처리한 평판에 대한 항력 감소 연구를 수행하였다. 딤플 표면에 의하여 난류 경계층 내에서 주유동 방향의 모멘텀이 증가하였으나 난류 강도 값에는 큰 변화가 없었다. 주유동에 대한 항력 측정은 후류 유속 측정결과를 이용하여 단면(profile) 저항을 계산하였고 6분력계를 이용하여 평판에 영향을 주는 항력을 직접 계측하였다. 후류의 유동장은 입자영상속도계(particle image velocimetry)를 이용하여 계측하였다. 딤플 처리된 평판에서 항력 감소율은 최대 4.6%의 값을 보였으며 106~107 정도의 레이놀즈 수 영역대에서 그 수가 증가하여도 항력이 지속적으로 증가하는 경향을 보였다
대형 캐비테이션 터널 내 선박 모형의 3차원 선체 반류 계측을 위한 레이저 유속계 개발
백부근,안종우,설한신,박영하,김기섭,전호근 대한조선학회 2017 大韓造船學會 論文集 Vol.54 No.6
Large Cavitation Tunnel (LCT) of KRISO enables us to conduct cavitation tests of the propeller attached to a ship model. As the ship model tests are done at rather high Reynolds number of 107~108, flow measurement system such as pitot tube cannot be employed because of structural safety problems in its system and difficulties in installing it within the test section. Thus, KRISO has developed new 3-D LDV system used in large test section of LCT. There are several difficulties in using 3-D LDV, which did not allow efficient operation of it. The first trouble was the calibration using the conventional pin hole. To make the focus with same laser-beam waists at the wanted position, the high spatial resolution CCD is utilized in the calibration procedure for 3-D LDV. The off-axis configuration provides two velocity components in the horizontal plane and on-axis configuration gives third velocity component in the vertical plane. The horizontal velocity components are also obtained in the coincidence mode, which prevents any misleading results in the off-axis configuration. The nominal wake of Aframax tanker model is measured by the developed 3-D LDV system. The measured hull wake showed good agreement with that obtained by CFD calculation.