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이경준(Kyongjun Lee),양경수(Kyung-Soo Yang),윤동혁(Dong-Hyeog Yoon) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5
Flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re =100 were numerically studied. We consider all possible 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 flow-induced forces are noticed depending on how the two circular cylinders are positioned, resulting in quantitative changes of force coefficients on both cylinders. Collecting all the numerical results obtained, we propose a contour diagram for drag coefficient and lift coefficient for each of the two cylinders. The perfect geometrical symmetry implied in the flow configuration allows one to use those diagrams to estimate flow-induced forces on two identical circular cylinders arbitrarily positioned in physical space with respect to the main flow direction.
두 개의 원형 실린더를 지나는 유동의 레이놀즈 수 효과
이경준(Kyongjun Lee),양경수(Kyung-Soo Yang),최춘범(Choon-Bum Choi) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.1
As a follow-up of our previous studies on flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100 and flow patterns past them,(1,2) we present Reynolds-number effects on the forces and patterns by further computing flows with Re=40, 50, 160. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the angle inclined with respect to the main flow direction. Collecting all the numerical results obtained, we propose contour diagrams for mean force coefficients and their rms of fluctuation as well as for flow patterns and Strouhal number for each Re. These diagrams shed light on a comprehensive picture on how the wake interaction between the two cylinders alters depending on Re.
두 개의 원형 실린더를 지나는 유동의 레이놀즈 수 효과
이경준(Kyongjun Lee),양경수(Kyung-Soo Yang),최춘범(Choon-Bum Choi) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10
As a follow-up of our previous studies on flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100(1) and flow patterns past them(2), we present Reynolds-number effects on the forces and patterns by further computing flows with Re=40, 50, 160. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the angle inclined with respect to the main flow direction. Collecting all the numerical results obtained, we propose contour diagrams for mean force coefficients and their rms of fluctuation as well as for flow patterns and Strouhal number for each Re. These diagrams shed light on a comprehensive picture on how the wake interaction between the two cylinders alters depending on Re.As a follow-up of our previous studies on flow-induced forces on two identical nearby circular cylinders immersed in the cross flow at Re=100 and flow patterns past them, we present Reynolds-number effects on the forces and patterns by further computing flows with Re=40, 50, 160. We consider all possible arrangements of the two circular cylinders in terms of the distance between the two cylinders and the angle inclined with respect to the main flow direction. Collecting all the numerical results obtained, we propose contour diagrams for mean force coefficients and their rms of fluctuation as well as for flow patterns and Strouhal number for each Re. These diagrams shed light on a comprehensive picture on how the wake interaction between the two cylinders alters depending on Re.
인접한 두 수중운동체 주위의 유동 해석을 위한 가상경계법의 적용
이경준(Kyongjun Lee),양경수(Kyung-Soo Yang) 대한기계학회 2012 대한기계학회 춘추학술대회 Vol.2012 No.11
Analysis of Fluid-structure interaction for two nearby underwater vehicles immersed in the sea is quite challenging because simulation of flow around them is very difficult due to the complexity of underwater vehicle shapes. The conventional approach using body-fitted or unstructured grids demands much time in dynamic grid generation, and yields slow convergence of solution. Since an analysis of fluid-structure interaction must be based on accurate simulation results, a more efficient way of simulating flow around underwater vehicles, without sacrificing accuracy, is desirable. An immersed boundary method facilitates implementation of complicated underwater-vehicle shapes on a Cartesian grid system. The 2<SUP>nd</SUP>-order spatial accuracy of our simulation is maintained with the aid of an adaptive mesh refinement technique. An LES modeling is also incorporated to resolve turbulent eddies. In this paper, we will demonstrate the effectiveness of the immersed boundary method we adopted, by presenting the simulation results on the flow around a modeled high-speed underwater vehicle interacting with a modeled low-speed one.
비정상 다상유동의 효율적 수치모사를 위한 VOF가 적용된 Franctional Step 기법
이경준(Kyongjun Lee),양경수(Kyung-Soo Yang),강창우(Changwoo Kang) 한국전산유체공학회 2010 한국전산유체공학회지 Vol.15 No.4
Fractional Step Methods(FSM) are popular in simulation of unsteady incompressible flow. In this study we demonstrate that FSM, combined with a Volume-Of-Fluid method, can be further applied to simulation of multiphase flow. The interface between the fluids is constructed by the effective least squares volume-of-fluid intelface reconstruction algorithm and advected by the velocity using the operator split advection algorithm. To verify our numerical methodology, our results are compared with other authors' numerical and experimental results for the benchmark problems, revealing excellent agreement. The present FSM sheds light on accurate simulation of turbulent multiphase flow which is found in many engineering applications.