• Journal of Korea Water Resources Association
• /
• v.38 no.8 s.157
• /
• pp.691-698
• /
• 2005

A series of experiments has been performed to investigate the flapping motion, which has been generally considered as an intrinsic characteristic of plane flow, of the horizontal merging buoyant jet discharged into stationary ambient water. For Horizontal merging buoyant jets, the flapping motions has been observed and the average onsets of flapping motion coincided with the start of merging transition. The Strouhal number, which describes the measure of frequency of vortices on the flow boundary with respect to the local properties of the flow, varies and converges to a constant value over merging transition. Considering the merging transition and the variation of local flow properties, the characteristics of flapping motion of plane flow can be applied to merging buoyant jets.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.50 no.11
• /
• pp.747-754
• /
• 2022

An experimental study was carried out to control a shock-induced boundary layer separation by utilizing the supersonic sweeping jet from the fluidic oscillator. High-speed schlieren, surface flow visualization, wall pressure measurement and precise Pitot tube measurement were applied to observe the influences of the location and the supply pressure of the fluidic oscillator on the characteristics of the oblique-shock-induced boundary layer separation. The characteristics of the separation control by the present supersonic fluidic oscillator was quantitatively analyzed by comparing with a conventional control method utilizing an air-jet vortex generator.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1998.04a
• /
• pp.486-491
• /
• 1998

본 연구에서는 충돌면의 형상에 따른 고속 원형 충돌제트의 불안정 모드를 밝히기 위하여 우선 충돌면의 형상에 따른 주파수 특성을 비교하고자 하였다. 이를 위해 충돌면이 제트의 직경보다 작은 원판(small plate)과 제트의 직경보다 큰 구멍(hole)의 2가지 경우에 대하여 실험을 하였고, 평판 충돌음에 대한 연구결과와 비교 검토하였다.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.24 no.4
• /
• pp.509-518
• /
• 2019

Analyses with various Sea Surface Temperature (SST) products indicate that the interannual variability of the area-averaged SST in the East/Japan Sea (EJS) is well correlated to that of Pacific Decadal Oscillation (PDO) during 1979-2018, especially in the autumn. The regression analysis with the wind vectors at 200 hPa, where the strongest jet stream flows, suggests that the long-term variability of the intensity as well as the meridional movement of the jet stream are related to the coupling of the autumn EJS SST and PDO. When the axis of the jet stream moves poleward (equatorward) with its weakening (strengthening), both the EJS SST and North Pacific SST increase (decrease). This suggests that both the intensity and meridional movement of the jet stream are possibly related to the coupling of the autumn EJS SST and PDO. However, effects of a weak jet stream during the summer and the strong East Asian winter monsoon make weak coupling between the EJS SST and PDO.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2007.05a
• /
• pp.355-355
• /
• 2007

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.10 no.1
• /
• pp.1-6
• /
• 1986

This paper presents a study on jet-flow-induced vibration, which has been one of the main causes of fuel damage in many pressurized water reactors. A systematic investigation was carried out experimently to identify the mechanism of jet-flow-induced vibration and to provide a design guide. Fluidelastic instability occurs when the jet velocity exceeds a critical value. The threshold of instability is given by V/f$_{n}$D=K.root.(D/h)(m$_{0}$.delta.$_{0}$/.sigma.D$^{2}$), where K is a stability constant. The effect of axial flow velocity and stand-off distance of a tube array on the stability of the array were investigated. A design guide is proposed.posed.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.1
• /
• pp.50-55
• /
• 2004

In this study, slit-tones by plane impinging jet are investigated experimentally over the whole subsonic flow range, especially at low speeds, in order to obtain the instability behaviour of impinging plane jet. Slit-tones are generated at low speeds associated with laminar shear layer instability as well as at high speeds associated with turbulent instability. Most of low-speed slit-tones are induced by symmetric mode instability unless the slit is not so wide, in which case antisymmetric modes are induced like edge-tones. It is found that the frequencies at low speeds ate controled by the unstable condition of the vortex at the nozzle exit and its pairings by which the frequencies are decreased by half. In the case of symmetric modes related with low-speed slit-tones, frequencies lower than those associated with one-step pairings are not found.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.1393-1398
• /
• 2000

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.2
• /
• pp.105-110
• /
• 2004

The objective of this study is to obtain the instability characteristics of the plane jet impinging on circular cylinder associated with the cylinder-tone. It is found that the characteristics depends upon he ratio of the cylinder diameter to the nozzle width, D/h, and the jet velocity. When the ratio is oderate the cylinder-tone is similar to the edge-tone. With increase of the ratio, its characteristics ecomes similar to that of the plate-tone in which only the high-speed tone associated with turbulent et is generated. When D/h 〈1. the frequency range, especially the lower limit of frequency, is ignificantly influenced by the cylinder diameter. At around D/h = 1/2, while low speed tones are nduced with the antisymmetric mode of instability and affected by the vortex shedding from the ylinder, high-speed tones are generated, at first, with the symmetric mode of instability. and then, ith antisymmetric mode, as the jet velocity increases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2002.05a
• /
• pp.824-829
• /
• 2002

Since many reciprocating and rotating components are attached to jet loom structure. it is exposed to a more vibration and moise problems than the other textile machinery. Thus the design of the jet loom frame is very important to characterize the dynamic response. In this study, a finite element model of jet loom main frame was developed to investigate the dynamic characteristics of jet loom. Two different finite element models of different main frames were constructed and these models were validated by the experimental results. Dynamic characteristics such natural frequencies and mode shapes were in good agreement between the finite element analysis and experimental results within 10% error range. It is expected that the result from this study can be used as the basic information of jet loom dynamic analysis and be extended for further analysis of forced response case.