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Vortex Dipole을 갖는 Stokes 유동의 자유표현 형상 해석
정재택 金烏工科大學校 1991 論文集 Vol.12 No.-
Two-dimensional slow viscous flow in a half space with free surface induced by locating a vortex dipole is investigated based on Stokes approximation. Surface tension effects are included but gravity is neglected. Complete solution is obtained by using conformal mapping. The velocity field throughout the fluid and the free surface shape are determined, which are depending of capillary number Ca.
Two-dimensional Stokes flow around a circular cylinder in a microchannel
정재택,윤석현 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.2
Two-dimensional Stokes flow around a circular cylinder in a microchannel is investigated based on Stokes approximation. The cylinderwith arbitrary radius translates along the centerline of the channel, and plane Poiseuille flow exists upstream and downstream fromthe cylinder. The translating velocity of the cylinder and the magnitude of the Poiseuille flow are arbitrary. The Stokes flow is examinedanalytically using Papkovich-Fadle eigenfunction expansion and least square method. The stream function and the pressure distributionof the flow field are obtained and shown for some typical cases. The force exerted on the cylinder and the pressure drop due to the cylinderare calculated as functions of the radius of the cylinder. For a small radius of the cylinder, the results of the force are coincident withprevious asymptotic expressions for the force. For a given average velocity of the Poiseuille flow in the channel, translational drift velocityof the cylinder is determined as a function of blockage factor. The drift velocity is slightly lower than the mean velocity of thePoiseuille flow component projected by the cylinder. The induced pressure drop due to the drifting cylinder in the Poiseuille flow is quitesmall. When the cylinder translates in the stagnant channel, a series of Moffatt eddies appears far from the cylinder in the channel, asexpected. The size of the primary eddy increases with the radius of the cylinder.
정재택(Jae-Tack Jeong),신수식(Soo-Sik Shin),김갑태(Kaptae Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.7
제로터는 유압모터나 펌프뿐만 아니라 조향장치인 파워 스티어링 유닛(PSU)에도 사용된다. 제로터의 내치차는 일상적인 경우 단일 원호형상의 외치차에 의하여 생성된다. 본 논문에서 PSU의 특성 개선을 위하여 보다 일반화 된 외치차의 형상으로부터 내치차를 생성하는 방법을 해석하였다. 해석의 결과로서, 외치차의 형상곡선이 특별한 2중곡률을 갖는 원호인 경우에 대하여, 내치차의 형상과 곡률, 제로터의 유량 및 접촉점의 위치와 슬립속도 등의 설계자료를 구하여 제시하였다. 이러한 해석은 새로운 PSU의 개발과 소형화를 가능케 한다. A gerotor is used in power-steering units (PSUs) as well as in hydraulic motors or pumps. The inner rotor is developed on the basis of the shape of the outer rotor tooth, which normally has one arc. The method of generating inner rotor on the basis of a generalized shape of outer rotor is analyzed with a view to improve PSU characteristics. An arc-shaped outer rotor with two curvatures was used in the analysis; design parameters such as the shape and curvature of the inner rotor, the flow rate of the gerotor, the position of contact point, and slip velocity are calculated, and these results are shown. This analysis enables us to develop a new design of compact PSUs.
정재택(Jae-Tack Jeong) 한국전산유체공학회 2016 한국전산유체공학회지 Vol.21 No.4
A two-dimensional Stokes flow past a circular disk in a circular tube is analyzed. The circular disk is located coaxially with the circular tube and the Hagen-Poiseuille flow exists at upstream and downstream far from the circular disk. The Stokes approximation is used and the flow is investigated analytically by using the method of eigenfunction expansion and the method of least square. From the analysis, the stream function and the pressure of the flow field are obtained, and the streamlines and pressure distribution are shown. Also, the pressure and shear stress distributions on the circular disk and circular tube wall are calculated, and shown for some typical radii of the circular disk. The additional pressure drop induced by the disk and the drag force exerted on the disk are compared as functions of the radius of the circular disk, and it is shown that the shear force on the wall of the tube increases due to the disk.
원관 내의 구형 기포를 지나는 축대칭 스톡스 유동에 대한 연구
정재택(Jae-Tack Jeong) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.5
원관 내의 기포를 지나는 비압축성 축대칭 유동에 대한 이론적 연구를 수행하였다. 기포는 원관의 중심축에 놓여 있으며, 기포에서 멀리 떨어진 곳에는 하겐-포아제 유동이 존재한다. 유동방정식에 스톡스 근사를 적용하고 고유 함수 전개와 오차의 최소제곱법을 사용하여 유동장을 해석하였다. 해석의 결과로 유동 함수와 압력 분포 식을 구하여 유선과 압력 분포도를 도시하였으며, 원관의 벽면과 기포표면에 작용하는 응력 분포를 계산하여 도시하였다. 원관 내의 기포로 인해 발생하는 부가적인 압력 강하와 기포가 받는 항력을 기포의 반경의 함수로 도시하였으며, 기포의 존재로 인하여 원관의 벽면에 작용하는 유동 방향의 전단력이 증가함을 확인하였다. This study analyzes the axisymmetric Stokes flow past a spherical bubble in a circular tube. The bubble is located on the axis of the circular tube, and the Hagen-Poiseuille flow exists upstream and downstream far from the bubble. The Stokes approximation is used, and the flow is investigated analytically using the eigenfunction expansion and the least-squared error methods. From the analysis, the stream function and pressure in the flow field are obtained, and the streamline pattern and pressure contour lines are shown. In addition, the normal and shear stress distributions on the bubble surface and circular tube wall are calculated, and then shown for some typical radii of the bubble. The additional pressure drop induced by the bubble and the drag force exerted on the bubble are plotted as functions of the bubble radius, and it is shown that the shear force on the tube wall increases owing to the existence of the bubble.