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성재용,이석종,신평호 한국공작기계학회 2008 한국공작기계학회 춘계학술대회논문집 Vol.2008 No.-
In this paper we describe an experimental method and an image processing technique for detecting the position of a meniscus in the micro capillary flows. The flow times of the meniscus in both cases of the ethylene glycol and glycerine were evaluated at the same temperature and position from the entrance of capillary tube. Physical properties of ethylene glycol and glycerine such as viscosity, surface tension, contact angle, which significantly impact on capillary force, were measured. As a result, it was found that a big change of viscosity and contact angle strongly influenced on the flow time inside the micro capillary tube.
Cinematic PIV 데이터의 3차원 위상평균 기법을 이용한 실린더 후류의 2차 와류 측정
성재용,유정열,Seong, Jae-Yong,Yu, Jeong-Yeol 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.11
Near-wake flow field downstream of a circular cylinder in the wake-transition regime where fine-scale secondary vortices have a spanwise wavelength of around one diameter has been studied by means of phase-averaging from cinematic PIV data. A cross-correlation algorithm in conjunction with the FFT(Fast Fourier Transform)analysis and an offset correlation technique is used for obtaining the velocity vectors. Which the help of very high sampling rate compared to the shedding frequency, it is possible to obtain phase-averaged flow fields although the shedding is not forced but natural. Phase -locked three-dimensional vortical structures are reconstructed form the phase-averaged data in one x-y(cross-sectional) and several z-x(spanwise-streamwise)planes. In this process of phase-averaging in a z-x plane, a technique to freeze the secondary vortices relative to the centerline is applied. The formation process of the secondary vortices is shown by considering spatial relations between the primary Karman and the secondary vortices and their temporal evolutions.
이동격자계에서 분리유한요소법에 의한 운동에너지 보존 알고리듬
성재용,최형권 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.11
Kinetic energy conservation for fixed and moving grids is examined in time-accurate finite element computation of fully unsteady inviscid flows. As numerical algorithms, fractional step method (FSM) and modified SIMPLE are used. To simulate the flow in moving grid system, arbitrary Lagrangian-Eulerian (ALE) method is adopted. In the present study, the energy conserving time integration rule for finite element algorithm is proposed and discussed schematically. It is shown that the discretization by Crank-Nicolson in time and Galerkin (central difference) in space must be used to ensure energy conservation. The developed code has been tested for a standing vortex in fixed or moving grid system, sloshing in a tank and propagation of a solitary wave, and has been shown to be a completely energy conserving algorithm.
PIV 유동 계측을 통한 천장형 실내기의 최적 제어 설계
성재용,안광협,이기섭,최호선,이인섭,Sung, Jae-Yong,An, Kwang-Hyup,Lee, Gi-Seop,Choi, Ho-Seon,Lee, In-Seop 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.8
A heating flow discharged from a 4-way ceiling type indoor unit has been investigated to determine the design parameters for the optimal flow control. The flow was measured by a PIV(particle image velocimetry) system and an experimental model of 1/10 scale with a transparent room was devised by satisfying the Archimedes number. This similarity is generally used in cases where the forced convection has similar magnitude of the natural convection. To optimize the heating flow, several vane angles and vane control algorithms of cross and right angle controls were considered. Regarding the vane angle, experimental results show that 30$^{\circ}$is an optimal angle to avoid re-suction flows without significant increase in flow noise. Temperature distribution measured in the environmental chamber ensures the increased thermal comfort when compared to the case, 60$^{\circ}$angle. At the optimal angle, applying open/close control gives rise to more uniform distribution of the heating flow than without control. Especially, the cross-control seems to be satisfactory for thermal comfort.