http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
3차원 Floquet 안정성 분석을 위한 가상 경계법의 적용
윤동혁(D.-H. Yoon),양경수(K.-S. Kang),최춘범(C.-B. Choi) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
An immersed boundary method(IBM, Kim et al.(2001)) for simulating flows over complex geometries is applied to computation of three-dimensional Floquet stability of a periodic wake. Floquet stability analysis is employed to extract different modes of three-dimensional instability. To verify the present method, a fully-resolved Floquet stability calculation for flow past a circular cylinder is considered. There are two different instability modes with long(mode A) and short (mode B) spanwise wavelengths for the periodic wake of a circular cylinder. The critical Reynolds number and the most unstable spanwise wavelengths of modes A and B are computed using the present method, and compared with other authors' results currently available.
윤동혁(D.-H. Yoon),양경수(K.-S. Yang),강창우(C. Kang) 한국전산유체공학회 2010 한국전산유체공학회 학술대회논문집 Vol.2010 No.5
A parametric study has been carried out to elucidate the characteristics of channel flow with a streamwise-periodic array of cylinders. This flow configuration is relevant to heat exchanger applications. The presence of cylinders in channel flow causes the attached wall boundary layer to separate, leading to significant change in flow instabilities. There exist two kinds of instabilities; flow undergoes a primary instability (Hopf bifurcaiton) at a lower Reynolds number, and the unsteady two-dimensional flow becomes unstable to three-dimensional disturbances at a higher Reynolds number. We report here the dependencies of the primary instability as well as the flow characteristics of the subsequent unsteady flow, including flow-induced forces and Strouhal number of vortex shedding, on the distance between the cylinder and the channel wall.
3차원 Floquet 안정성 분석을 위한 가상 경계법의 적용
윤동혁(D.-H. Yoon),양경수(K.-S. Yang) 한국전산유체공학회 2009 한국전산유체공학회지 Vol.14 No.4
An immersed boundary method(IBM, Kim et al.(2001)) for simulating flows over complex geometries is applied to computation of three-dimensional Floquet stability of a periodic wake. Floquet stability analysis is employed to extract different modes of three-dimensional instability. To verify the present method, a fully-resolved Floquet stability calculation for flow past a circular cylinder is considered. There are two different instability modes with long(mode A) and short (mode B) spanwise wavelengths for the periodic wake of a circular cylinder. The critical Reynolds number and the most unstable spanwise wavelengths of modes A and B are computed using the present method, and compared with other authors' results currently available.
원형 실린더가 주기적으로 배열된 채널 유동의 주 유동 불안정성
윤동혁(D.-H. Yoon),양경수(K.-S. Yang),강창우(C. Kang) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.3
A parametric study has been carried out to elucidate the characteristics of channel flow with a stream wise-periodic array of cylinders. This flow configuration is relevant to heat exchanger applications. The presence of cylinders in channel flow causes the attached wall boundary layer to separate, leading to significant change in flow instabilities. There exist two kinds of instabilities; flow undergoes a primary instability (Hopf bifurcation) at a lower Reynolds number, and the unsteady two-dimensional flow becomes unstable to three-dimensional disturbances at a higher Reynolds number. We report here the dependencies of the prim my instability as well as the flow characteristics of the subsequent unsteady flow, including flow-induced forces and Strouhal number of vortex shedding, on the distance between the cylinder and the channel wall.
한태헌(T.H. Han),양경수(K.S. Yang),윤동혁(D.H. Yoon),이경준(K. Lee) 한국전산유체공학회 2008 한국전산유체공학회지 Vol.13 No.2
Heat transfer on two identical nearby circular cylinders immersed in the uniform cross flow at Re=120 and Pr=0.7 was numerically studied. We consider all possible types of arrangements of the two circular cylinders in terms of the distance between the two cylinders and the inclination angle with respect to the direction of the main flow. It turns out that significant changes in the characteristics of heat transfer are noticed depending on how the two circular cylinders are positioned, resulting in quantitative changes of heat transfer coefficients on both cylinders. Collecting all the numerical results obtained, we propose a contour diagram for averaged Nusselt number for each of the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use those diagrams to estimate heat transfer rates on two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.
횡방향으로 정렬된 2개의 정사각주 후류에서의 3차원 불안정성
최춘범(C.-B. Choi),장용준(Y.-J. Jang),윤동혁(D.-H. Yoon),양경수(K.-S. Yang) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Three-dimensional linear instability in the flow past two square cylinders in side-by-side arrangements are numerically studied by using a Floquet analysis. The distance between the neighboring faces of the two cylinders (G) is the key parameter which affects the secondary instability under consideration. In this paper, we plan to present the critical Reynolds number for the three-dimensional instability and the corresponding spanwise wave number of the most unstable (or least stable) wave for each G. Our results would shed light on a complete understanding of the onset of three-dimensional instability in the presence of two side-by-side square cylinders.
수직방향으로 정렬된 정사각주 후류에서의 3차원 불안정성
최춘범(C.-B. Choi),장용준(Y.-J. Jang),윤동혁(D.-H. Yoon),양경수(K.-S. Yang) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.2
Secondary instability in the flow past two square cylinders in side-by-side arrangements is numerically studied by using a Floquet analysis. The distance between the neighboring faces of the two cylinders (G) is the key parameter which affects the secondary instability under consideration. In this paper, we present the critical Reynolds number for the secondary instability and the corresponding spanwise wave number of the most unstable (or least stable) wave for each G. Our results would shed light on a complete understanding of the onset of secondary instability in the presence of two side-by-side square cylinders.