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표면 와류 분포 방법을 이용한 아음속 풍동의 2차원 수축부 설계
金學奉 한국항공대학교 1986 論文集 Vol.24 No.-
A design method for the two-dimensional wind Tunnel contractions of finite length have been developed using surface vortex distribution method with given velocity distribution and contraction ratio. The integral eguation for the wall shape is solved by means of numerical and iterative method. Some design examples are presented to compare with other design methods. The results show that the present method may be used to design two-dimensional contracting duct with good exit velocity uniformity and with desired wall pressure gradient, duct length and contraction ratio.
비정열 격자계에서 타원형 방정식의 수치해석을 위한 다중격자 가속
김학봉 한국항공대학교 1998 論文集 Vol.36 No.-
The multigrid method have been considered the most effective, especially when used to solve strongly eliptic problems. Unstructured grids have evolved over the recent years as a very variable approach for modeling complex geometries since they have been found to be very efficient means of generating body-conforming grids for complex configurations. The complete lack of order in unstructured grids precludes any possibility of generating suceccessively coarser grids. In the present works, the fine grids are created by division of trangular coarser grid cells. Thus, the cell-tree data structure is used to retrace the parents of fine cells on the adapted grid, and these parent cells along with the cells in the unembeded region of the flow domain constitute the coarser grid of multigrid of multigrid. The edge-tree data structure is used to interpolate the residuals back and forth between the fine and casrser level grids, and hence the scheme avoids relatively complicated intergrid transfer algorithms imployed in the other multigrid schemes. The purpose of this works is to extend the multigrid techniques historically employed by structured grid algorithms to unstructured solvers to accelerate convergence rates of the elliptic equation solver that is based on a finite volume cell-centered approach.
김학봉,이영진,김영일,임종인,노용래 경북대학교 센서기술연구소 1995 연차보고서 Vol.1995 No.-
첫째, 압전단결정 LiTaO_3에 대하여 SAW 전파 방향을 결정하였고 그에 따라 SAW소자를 제작하여 그 제반 특성의 이론적, 실험적 검증을 완료하였다 둘째, SAW oscillator 및 digital frequency counter를 제작하여 SAW 센서 system을 개발하였다. Up to the present, we have finished developing (1) optimal SAW propagation path on the LiTaO_3 single crystals and optimal IDT patterns whose properties have been verified theoretically and experimentally, and (2) SAW sensor system that incorporate all the capabilities of measurement, analysis, and display within one system.