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김연환(Yeon-Whan Kim),배용채(Yong-Chae Bae),이두영(Doo-Young Lee) 한국소음진동공학회 2012 한국소음진동공학회 학술대회논문집 Vol.2012 No.10
The downstream piping system of the water supply system in a supercritical power plant is affected by the fluctuation pressure waves induced by accessing to the acoustic modes of the piping systems with the rotation and impeller passing pulsations of the feed water pump. There are the phenomena amplified at the same time in the range of 415 ~ 455Hz, 830 ~ 910Hz, 1245 ~ 1365Hz and 1660 ~ 1820Hz on the spectrums of the vibration, the sound pressure, and the pressure fluctuation waves.
와류와 전향계단의 상호작용에 의한 비정상 벽면압력 변동의 수치해석
유기완,이준신 한국소음진동공학회 2002 한국소음진동공학회 논문집 Vol.12 No.3
Modifying effects of the rectangular forward step for suppressing the unsteady pressure fluctuation during interaction between the upstream vortical flow and the edge are studied numerically. The vertical flow is modeled by a point vortex, and the unsteady pressure coefficient is obtained from the velocity and the potential fields. To investigate the effects of the edge shape the rectangular forward step is chamfered wish various angles. Calculation shows that the pressure peaks become decreased by increasing the vortex height as well as the chamfering angle. The pressure amplitudes are very sensitive to the change of the initial vertex height and its strength. From this study we can find out that the chamfered edge has two effects; the one is that it suppresses the pressure amplitude generated from the edge, and the other is that it decreases the time variation of unsteady pressure fluctuation. These modifying concepts can be applied to attenuate the self-sustained oscillation mechanism at the open cavity flow.
프로펠러의 날개 수 변경에 의한 432톤급 카페리여객선 선실 진동 개선에 대한 사례 연구
윤현우(Hyunwoo Yun),버광 다오(Vougang Dao),이돈출(Donchool Lee) 한국소음진동공학회 2014 한국소음진동공학회 학술대회논문집 Vol.2014 No.10
Recently, car-ferry passenger ships of navigating the coast area in the inside of our country are on an increasing trend of main engine power and the height of upper structure, which is increased to ships speed and loading of large vehicles. The most ship with high-speed main engine is happened to excessive vibration by propeller induced excitation force on account of connecting the vibration of hulls girder and the upper structure by decreasing the shear stiffness and natural frequency for increasing the height of passenger deck. In this paper, By exchanging the propeller of alteration the number of blades, it could be keep to ships speed and its decreased the vibration of hull part that is located passenger deck on the upper deck, which is identified by countermeasure of protection against vibration to procure the safety ships navigation through measuring the vibration of hull structure.
내부 무장창의 비정상 유동 거동 분석을 위한 수치적 연구
김덕현(D.H. Kim),유주열(J.Y. You),권오준(O.J. Kwon) 한국전산유체공학회 2012 한국전산유체공학회 학술대회논문집 Vol.2012 No.5
In the present study, numerical investigations of unsteady flow field in a three-dimensional weapons bay have been conducted. The Weapons Internal Carriage Separation (WICS) cavity bay with a length-to-depth ratio of 4.5 was chosen for the cavity geometry. The Free-stream Mack number was 0.95 and the Reynolds number was 3.75×10<SUP>6</SUP>. The unsteady turbulent flow over a rectangular cavity was simulated using the k-ω Shear Stress Transport(SST) and the Detached Eddy Simulation(DES) based on unstructured meshes. The result of the SST-DES showed better agreement with the experiment at high frequency than that of the k-ω SST. It is shown that the unsteadiness inside the cavity was caused by detaching and reattaching processes of the shear layer, and the high frequency content was produced by the transversal fluctuation of the shear layer as a three-dimensional effect.