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Donghyun You - One of the best experts on this subject based on the ideXlab platform.
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study of Vortex Shedding induced vibration of a flexible splitter plate behind a cylinder
Physics of Fluids, 2013Co-Authors: Jinmo Lee, Donghyun YouAbstract:A computational analysis of Vortex-Shedding-induced vibration of a flexible splitter plate behind a cylinder at a low Reynolds number is conducted to understand effects of the length and flexibility of a splitter plate on the drag and lift of a cylinder and vibration of the attached plate. The drag and lift coefficients, the Strouhal number of Vortex Shedding, and the magnitude of tip displacements of a flexible splitter plate are found to be intricate functions of the plate flexibility. The deflection shape of a flexible splitter plate is dependent on the length of the plate, while the deflection magnitude is a function of the bending stiffness and natural frequencies of the corresponding plate. It is concluded in the present work that the Strouhal number of Vortex Shedding or the frequency of plate deflection is difficult to estimate using natural frequencies of the plate, which are calculated by inducing free vibration, since the fluid loading is distributed non-uniformly over the plate rather than con...
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study of Vortex Shedding induced vibration of a flexible splitter plate behind a cylinder
ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th Internationa, 2012Co-Authors: Jinmo Lee, Donghyun YouAbstract:Integrated computational fluid dynamics (CFD) and computational structural dynamics (CSD) simulations of flow over a cylinder with a flexible splitter plate attached to the rear stagnation point, are performed. Flow over a cylinder produces Vortex Shedding, which causes unsteady pressure and shear stress distributions over a flexible splitter plate. As a result, the flexible splitter plate vibrates with distinct frequencies, which are different from the Vortex-Shedding frequency and natural frequencies of the plate. A systematic and detailed analysis of the effects of the flexible plate on fluid-structure dynamics and on the drag and lift of the cylinder, is presented.Copyright © 2012 by ASME
Jinmo Lee - One of the best experts on this subject based on the ideXlab platform.
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study of Vortex Shedding induced vibration of a flexible splitter plate behind a cylinder
Physics of Fluids, 2013Co-Authors: Jinmo Lee, Donghyun YouAbstract:A computational analysis of Vortex-Shedding-induced vibration of a flexible splitter plate behind a cylinder at a low Reynolds number is conducted to understand effects of the length and flexibility of a splitter plate on the drag and lift of a cylinder and vibration of the attached plate. The drag and lift coefficients, the Strouhal number of Vortex Shedding, and the magnitude of tip displacements of a flexible splitter plate are found to be intricate functions of the plate flexibility. The deflection shape of a flexible splitter plate is dependent on the length of the plate, while the deflection magnitude is a function of the bending stiffness and natural frequencies of the corresponding plate. It is concluded in the present work that the Strouhal number of Vortex Shedding or the frequency of plate deflection is difficult to estimate using natural frequencies of the plate, which are calculated by inducing free vibration, since the fluid loading is distributed non-uniformly over the plate rather than con...
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study of Vortex Shedding induced vibration of a flexible splitter plate behind a cylinder
ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th Internationa, 2012Co-Authors: Jinmo Lee, Donghyun YouAbstract:Integrated computational fluid dynamics (CFD) and computational structural dynamics (CSD) simulations of flow over a cylinder with a flexible splitter plate attached to the rear stagnation point, are performed. Flow over a cylinder produces Vortex Shedding, which causes unsteady pressure and shear stress distributions over a flexible splitter plate. As a result, the flexible splitter plate vibrates with distinct frequencies, which are different from the Vortex-Shedding frequency and natural frequencies of the plate. A systematic and detailed analysis of the effects of the flexible plate on fluid-structure dynamics and on the drag and lift of the cylinder, is presented.Copyright © 2012 by ASME
E W Hendricks - One of the best experts on this subject based on the ideXlab platform.
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feedback control of von karman Vortex Shedding behind a circular cylinder at low reynolds numbers
Physics of Fluids, 1994Co-Authors: D S Park, D M Ladd, E W HendricksAbstract:A computational study of the feedback control of von Karman Vortex Shedding behind a circular cylinder at low Reynolds numbers is reported. The two‐dimensional Navier–Stokes equations with feedback are solved numerically. The control actuators are a pair of blowing/suction slots located at ±110° from the leading stagnation point. A single feedback sensor is used and the actuators are 180° out of phase with each other. Complete suppression of Vortex Shedding is achieved for the simulation at Reynolds number Re=60. The suppression window in the feedback sensor location xs is narrow. With the feedback sensor location fixed at the optimum location, Vortex Shedding becomes suppressed with increasing feedback gain α. However, further increase of the feedback gain destabilizes the flow again. At Reynolds number Re=80, and above, the feedback control stabilizes the primary Vortex Shedding mode, but a secondary mode which may be lower or higher in frequency than the primary depending upon the phase of the feedback...
K M Lam - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of Vortex Shedding from an inclined flat plate
Engineering Applications of Computational Fluid Mechanics, 2010Co-Authors: K M Lam, C T WeiAbstract:Abstract:Vortex Shedding flow from a flat plate inclined to a uniform flow at an angle of attack between 20o and 45o is simulated with a finite volume CFD code with RNG k-ω turbulence model. The unsteady flow simulation at Re=2X104 with RANS shows two trains of vortices shed from the two different edges of the plate forming a Vortex street in the wake of the plate. The computed results provide support to previous experimental observations that in this asymmetric flow geometry, the two trains of vortices in the Vortex street possess different Vortex strengths. There is further evidence that the Vortex from the plate leading edge is actually shed from a location near the trailing end of the plate. The computed flow at successive phases of a Vortex Shedding cycle show different development and Shedding mechanisms for the two trains of vortices. The study also explores the generation mechanism of the fluctuating lift and drag on the plate and its relationship with the Vortex Shedding processes.
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Vortex Shedding flow behind a slowly rotating circular cylinder
Journal of Fluids and Structures, 2009Co-Authors: K M LamAbstract:Abstract This paper investigates flow past a rotating circular cylinder at 3600⩽Re⩽5000 and α⩽2.5. The flow parameter α is the circumferential speed at the cylinder surface normalized by the free-stream velocity of the uniform cross-flow. With particle image velocimetry (PIV), Vortex Shedding from the cylinder is clearly observed at α
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asymmetric Vortex Shedding flow past an inclined flat plate at high incidence
European Journal of Mechanics B-fluids, 2005Co-Authors: K M Lam, M Y H LeungAbstract:Abstract This paper reports an experimental investigation of the Vortex Shedding wake behind a long flat plate inclined at a small angle of attack to a main flow stream. Detailed velocity fields are obtained with particle-image velocimetry (PIV) at successive phases in a Vortex Shedding cycle at three angles of attack, α=20°, 25° and 30°, at a Reynolds number Re≈5,300. Coherent patterns and dynamics of the vortices in the wake are revealed by the phase-averaged PIV vectors and derived turbulent properties. A Vortex street pattern comprising a train of leading edge vortices alternating with a train of trailing edge vortices is found in the wake. The trailing edge Vortex is shed directly from the sharp trailing edge while there are evidences that the formation and Shedding of the leading edge Vortex involve a more complicated mechanism. The leading edge Vortex seems to be shed into the wake from an axial location near the trailing edge. After Shedding, the vortices are convected downstream in the wake with a convection speed roughly equal to 0.8 the free-stream velocity. On reaching the same axial location, the trailing edge Vortex, as compared to the leading edge Vortex, is found to possess a higher peak vorticity level at its centre and induce more intense fluid circulation and Reynolds stresses production around it. It is found that the results at the three angles of attack can be collapsed into similar trends by using the projected plate width as the characteristic length of the flow.
Haecheon Choi - One of the best experts on this subject based on the ideXlab platform.
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Control of laminar Vortex Shedding behind a circular cylinder using tabs
Journal of Mechanical Science and Technology, 2014Co-Authors: Jeeun Yoon, Haecheon ChoiAbstract:Small, thin flat plates (called tabs hereafter) are attached to the upper and lower surfaces of a circular cylinder to control Vortex Shedding and reduce the mean drag and lift fluctuations at the Reynolds number of 100. We vary the location and size of the tabs and the distance between the adjacent tabs. The maximum amount of drag reduction by the tabs is 17%. It is found that the tabs perturb twodimensional Vortex Shedding and introduce spanwise mismatch of Vortex Shedding, which weakens the strength of Vortex Shedding or even annihilates Vortex Shedding. The present result suggests that these tabs are an effective passive device for the control of Vortex Shedding behind two-dimensional bluff bodies.
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suboptimal feedback control of Vortex Shedding at low reynolds numbers
Journal of Fluid Mechanics, 1999Co-Authors: Chulhong Min, Haecheon ChoiAbstract:The objective of this study is to develop a method of controlling Vortex Shedding behind a bluff body using control theory. A suboptimal feedback control procedure for local sensing and local actuation is developed and applied to the flow behind a circular cylinder. The location of sensors for feedback is limited to the cylinder surface and the control input from actuators is the blowing and suction on the cylinder surface. Three different cost functionals to be minimized ( J 1 and J 2 ) or maximized ( J 3 ) are investigated: J 1 is proportional to the pressure drag of the cylinder, J 2 is the square of the difference between the target pressure (inviscid flow pressure) and real flow pressure on the cylinder surface, and J 3 is the square of the pressure gradient on the cylinder surface, respectively. Given the cost functionals, the flow variable to be measured by the sensors and the control input from the actuators are determined from the suboptimal feedback control procedure. Several cases for each cost functional have been numerically simulated at Re = 100 and 160 to investigate the performance of the control algorithm. For all actuations, Vortex Shedding becomes weak or disappears, and the mean drag and drag/lift fluctuations significantly decrease. For a given magnitude of the blowing/suction, reducing J 2 provides the largest drag reduction among the three cost functionals.
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control of laminar Vortex Shedding behind a circular cylinder using splitter plates
Physics of Fluids, 1996Co-Authors: Kiyoung Kwon, Haecheon ChoiAbstract:Laminar Vortex Shedding behind a circular cylinder and its control using splitter plates attached to the cylinder are simulated. The Vortex Shedding behind a circular cylinder completely disappears when the length of the splitter plate is larger than a critical length, and this critical length is found to be proportional to the Reynolds number. The Strouhal number of the Vortex Shedding is rapidly decreasing with the increased plate length until the plate length (l) is nearly the same as the cylinder diameter (d). On the other hand, at 1
Reynolds numbers investigated. The net drag is significantly reduced by the splitter plate, and there exists an optimum length of the plate for minimum drag at a given Reynolds number. From an examination of the instantaneous flow fields, it is found that the Strouhal number modification by the splitter plate is closely related to the size of the primary Vortex behind the cylinder and the length of the plate.
