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흐름에 대하여 橫方向으로 놓인 두 원통둘레의 Potential flow 硏究
徐龍權 영남이공대학 1981 論文集 Vol.10 No.-
This paper treats the potential flow of the ideal fluid passing the cylinders placed laterally. The Laplace equation is solved by adequate coordinate trans-formation and with boundary conditions. The stream function is calculated and graphed, after which pressure distribution on the body surface, the lift coefficient and the stagnation point are also deduced and shown on this paper. Followings are concluded from these results. 1) Stream lines are more inclined to the outer direction than those of the single cylinder. 2) The flow is the fastest in the midst of the two bodies. This makes the two cylinders attract each other and the attraction force increases as the two bodies got nearer. 3) Stagnation point goes toward the mid poind of the two cylinders as the two get nearer.
배경회전하에서 형성되는 주기적 유동의 3차원 수치해석과 실험
서용권,박재현,Suh, Yong-Kweon,Park, Jae-Hyun 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.5
We present numerical and experimental results of periodic flows inside a rectangular container under a background rotation. The periodic flows are generated by changing the speed of rotation periodically so that a time-periodic body forces produce the unsteady flows. In numerical computation, a parallel-computation technique with MPI is implemented. Flow visualization and PIV measurement are also performed to obtain velocity fields at the free surface. Through a series of numerical and experimental works, we aim to clarify, if any, the fundamental reasons \ulcornerf discrepancy between the two-dimensional computation and the experimental measurement, which was detected in the previous study for the same flow model. Specifically, we check if the various assumptions prerequisite for the validity of the classical Ekman pumping law are satisfied for periodic flows under a background rotation.
마이크로채널 내 블록의 정렬과 구조변경에 따른 교반특성
서용권,허형석,Suh, Yong-Kweon,Heo, Hyeung-Seok 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.7
Numerical study on stirring characteristics in a microchannel with blocks arranged periodically has been performed. Viscous flows through the microchannel is simulated three-dimensionally using a commercial code, FLUENT 6.0. Focus is given to the effect on the stirring characteristics of the geometric factors including the pitch, height and angle of the block arrangement. The numerical results at low Reynolds numbers show that the particles' trajectories in the microchannel heavily depend on the block arrangement. A nonlinear dynamical tool, i.e. Lyapunov exponent, was used in analysing the mixing effect. It was found that the mixing is the most effective at a certain combination of parameter values.
서용권,김현민,Seo,Yong-Gwon,Kim, Hyeon-Min 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.12
A fluid flow inside a circular cylinder subject to horizontal and circular oscillation is analyzed theoretically. Under the assumption of small-amplitude oscillation, the governing equations take linear forms. The velocity field is obtained in terms of the first kind of Bessel function of order 1. It was found that a particle describes an orbit close to a circle in the central region and an arc near the side wall. We also obtained the Stokes' drift velocity induced by the traveling wave along the circumferential direction. The Eulerian streaming velocities at the edge of the bottom and side boundary layers were also obtained. It was shown that the vertical component of the steady streaming velocity on the side wall is almost proportional to the amplitude of the free surface motion.
비정상 Navier-Stokes 방정식의 수치해석을 위한 다단계 외재법의 성능 비교
서용권,Seo,Yong-Gwon 대한기계학회 1997 大韓機械學會論文集B Vol.21 No.2
In this study, performance of the multi-stage explicit methods for numerical computation of the unsteady Navier-Stokes equations is investigated. Three methods under consideration are 1 st-, 2 nd-, and 4 th-order Runge-Kutta (R-K) methods. Compared in this estimation is stability, accuracy, and CPU time of each method. The computational codes developed are applied to the two-dimensional flow in a square cavity driven by an oscillating lid. It turned out that at Reynolds number 400, the 1 st-order R-K method is the best, while at 3200 the 2 nd-order R-K is recommended. At higher Reynolds numbers, it is conjectured that the 4 th-order R-K method will be the best algorithm among three due to its highest stability.
서용권,Suh, Y.K. 대한설비공학회 1992 설비공학 논문집 Vol.4 No.4
A two-dimensional Benard-convection system with a phase-change material inside has been analysed. The main purpose of the present study is to clarify the basic reason of the hysteresis found by the previous investigators. The interface between the solid and the liquid is assumed to be planar. The analysis was performed with heat transfer rates under the steady state on the interface. It was found that the hysteresis occurs due to the abrupt increase in the heat transfer rate at the onset of natural convection in the classical Benard-convection system. The spectral method was applied to obtain the steady solution of the natural convection for the specific material and to confirm the hysteresis phenomenon.