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원형단면 실린더를 지나는 유동에 대한 자유류 난류 강도의 영향
양경수,이상산,이승수,이준식,황종연 대한기계학회 2004 大韓機械學會論文集B Vol.28 No.8
In this study, the effects of freestream turbulence intensity on laminar-turbulent transition of separated shear layers in the wake of a circular cylinder are investigated using an immersed boundary method and LES. It is shown that the present numerical results without freestream turbulence for Re=3,900 based on bulk mean velocity and the cylinder diameter are in good agreement with other authors' experimental observations and numerical results, verifying our numerical methodology. Then a 'prescribed power spectrum' method is imposed to generate isotropic turbulence at the inlet of the computational domain at each time step. The principal effects of freestream turbulence intensity on flow statistics are investigated for Re=3,900. Statistical study reveals that the Reynolds stresses in the near-wake region gradually increase, and transition occurs further upstream, as the turbulence intensity increases. On the other hand, the bubble size behind the cylinder decreases as the turbulence intensity increases, which indicates that the freestream turbulence helps mean velocity be quickly recovered.
어머니의 취업유무와 아동의 자아개념이 행동문제에 미치는 영향
양경수 한국아동교육학회 2002 아동교육 Vol.11 No.2
The purpose of this study is the investigation of the effect of a mother's employment and children self-conception on the behavior problem. We made up questions of children's problem behavior for 340 of elementary school students, including 182 boys and 168 girls, in the fourth, fifth, and sixth grade on this purpose. We estimated behavior problem by using a scale of behavior estimation modified by Han Mi-Hyun(1996), developed by Achenbach(1991) for four to eighteen year korean children. The reliability of the scale is .89. We also estimated the children self-conception by using a test developed by Kim Jung-Gyu(1992) and based on Shabelson & Bolus model of self-perception structure(1982) of which the reliability is .90. MAVOVA was used as a statistic method to investigate data, and the results are as follows. Ⅰ. Academic self-concept and social self-concept for the children with employed mother are higher than those with unemployed mother. Ⅱ. The children with employed mother showed more hyperactivity than those with unemployed mother. Ⅲ. Children with low self-conception showed more anxious behavior, withdrawal behavior, and immature behavior than those with high self-conception. Ⅳ. There's no interaction between the mother's employment and children self-perception in the behavior problem.
양경수,Yang, Gyeong-Su 대한기계학회 1996 大韓機械學會論文集B Vol.20 No.9
Transitional flow in an obstructed channel is investigated using numerical simulation. Two-dimensional thin obstacles are mounted symmetrically in the vertical direction and periodically in the streamwise direction. Flow separation occurs at the tip of the sharp obstacles. Depending on the Reynolds number, the flow undergoes Hopf bifurcation as the primary instability leading to a two-dimensional unsteady periodic solution. At higher Reynolds numbers, the unsteady solution exhibits a symmetry-breaking bifurcation which results in an unsteady asymmetric solution. The results are compared with experiments currently available, and show a good agreement.
양경수 대한기계학회 1994 大韓機械學會誌 Vol.34 No.9
이 글에서는 난류유동의 수치모사 기법으로서 최근 주목을 받고 있는 LES에 대해서 살펴보았다. LES의 개념은 공간에서의 여고에 근거를 두고 있으며 따라서 난류모델은 작은 스케일의 유동 구조에만 국한된다. LES의 이러한 장점은 DNS에 좀도 가까운 난류모델링의 가능성을 의미한다. 또한 그간 발전된 LES의 기법들에 대해 고찰해보았으며 LES는 DNS의 처선책으로서 난류유 동을 예측하기 위한 도구로서 그 전망은 매우 밝다.