Control And Suppression Of Laminar Vortex Shedding Off Two Dimensional Bluff Bodies
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Control And Suppression Of Laminar Vortex Shedding Off Two Dimensional Bluff Bodies
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Author : Andre Sirilutporn Chan
language : en
Publisher:
Release Date : 2012
Control And Suppression Of Laminar Vortex Shedding Off Two Dimensional Bluff Bodies written by Andre Sirilutporn Chan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
The focus of this research is on the control and suppression of vortex shedding of flow past bluff bodies. The motivation of this research stems from the aerodynamic problems encountered in the design and development of hard disk drives (HDD's). Two different computational fluid dynamic methods have been used in this research-- the Semi-Implicit Method for Pressure Linked Equation (SIMPLE), that is widely employed in today's commercial incompressible flow solvers, and the high-order spectral difference (SD) method, recently developed for compressible flow solution. In addition to numerical simulation and verification, complementary experimental measurements have been performed to further validate the results. This research leads to two very different suppression techniques: 1) a passive control using a thin splitter plate positioned downstream of the bluff body; 2) an active control by way of counter rotating a cylinder pair. The passive suppression technique places a thin splitter plate downstream of the bluff body in order to interfere with the vortex wakes and thereby suppress the vortexinduced forces on the bluff body itself. The present investigation examines the suppression of wake instabilities in the laminar shedding regime. Both bounded and unbounded flow conditions are examined. It is found that in the bounded flow condition, the channel walls have an additional stabilizing effect on the shedding control. With proper positioning of the splitter plate, vortex shedding is completely suppressed in a bounded flow with moderate blockage factor. Wind tunnel empirical experiments have also confirmed the effectiveness of a splitter plate in a bounded flow. Active flow control by counter-rotating a pair of cylinders has been numerically investigated. It has also been investigated experimentally in partnership with the Gas Dynamics Laboratory at Princeton University. It is demonstrated that it is possible to suppress unsteady vortex shedding for gap sizes from one to five cylinder diameters, at Reynolds numbers from 100 to 200. The degree of unsteady wake suppression is proportional to the speed and the direction of rotation, and there is a critical rotation rate where a complete suppression of flow unsteadiness can be achieved. In the doublet-like configuration at higher rotational speeds, a virtual elliptic body that resembles a potential doublet is formed, and the drag is reduced to zero. The shape of the elliptic body primarily depends on the gap between the two cylinders and the speed of rotation. Prior to the formation of the elliptic body, a second instability region is observed, similar to that seen in studies of rotating single cylinders. It is also shown that the unsteady wake suppression can be achieved by rotating each cylinder in the opposite direction, that is, in a reverse doublet-like configuration. This tends to minimize the wake interaction of the cylinder pair and the second instability did not make an appearance over the range of speeds investigated here.
An Experimental Study Of The Origin Of Oblique Vortex Shedding From Two Dimensional Bluff Bodies
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Author : Mustapha Hammache
language : en
Publisher:
Release Date : 1990
An Experimental Study Of The Origin Of Oblique Vortex Shedding From Two Dimensional Bluff Bodies written by Mustapha Hammache and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with categories.
Modeling And Simulation Techniques In Structural Engineering
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Author : Samui, Pijush
language : en
Publisher: IGI Global
Release Date : 2016-08-12
Modeling And Simulation Techniques In Structural Engineering written by Samui, Pijush and has been published by IGI Global this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-08-12 with Technology & Engineering categories.
The development of new and effective analytical and numerical models is essential to understanding the performance of a variety of structures. As computational methods continue to advance, so too do their applications in structural performance modeling and analysis. Modeling and Simulation Techniques in Structural Engineering presents emerging research on computational techniques and applications within the field of structural engineering. This timely publication features practical applications as well as new research insights and is ideally designed for use by engineers, IT professionals, researchers, and graduate-level students.
Research On Bluff Body Vortex Wakes
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Author :
language : en
Publisher:
Release Date : 1995
Research On Bluff Body Vortex Wakes written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1995 with categories.
Comparison of laboratory experiments and computational results for two dimensional flows showed that, in impulsively started flows, laboratory flows are two dimensional in the early stages and that three dimensional effects develop after acceleration is complete. In fully developed flow the mean and fluctuating forces are considerably lower (up to 50%) in the laboratory flows (ie with three dimensionality) than in the two dimensional numerical simulations. The experiments in tow tank and water tunnel also revealed the existence of long-time modulations of vortex shedding forces. These have the form of bursts with duration of order 10 vortex shedding periods. A novel method of introducing controlled spanwise components of velocity into otherwise two dimensional flow, at low Reynolds number was to give the cylinder an axial (spanwise) motion, either a steady translation or a periodic oscillation. For unsteady, periodic axial oscillation of the cylinder, the experiments showed how the ratio of the spanwise period to the vortex shedding period determines the patterns of vortex dislocation in the wake, how regimes of chaos are formed and how shedding frequency and wake spectra are affected. (AN).
Encyclopedia Of Ocean Engineering
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Author : Weicheng Cui
language : en
Publisher: Springer Nature
Release Date : 2022-06-29
Encyclopedia Of Ocean Engineering written by Weicheng Cui and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2022-06-29 with Technology & Engineering categories.
This encyclopedia adopts a wider definition for the concept of ocean engineering. Specifically, it includes (1) offshore engineering: fixed and floating offshore oil and gas platforms; pipelines and risers; cables and moorings; buoy technology; foundation engineering; ocean mining; marine and offshore renewable energy; aquaculture engineering; and subsea engineering; (2) naval architecture: ship and special marine vehicle design; intact and damaged stability; technology for energy efficiency and green shipping; ship production technology; decommissioning and recycling; (3) polar and Arctic Engineering: ice mechanics; ice-structure interaction; polar operations; polar design; environmental protection; (4) underwater technologies: AUV/ROV design; AUV/ROV hydrodynamics; maneuvering and control; and underwater-specific communicating and sensing systems for AUV/ROVs. It summarizes the A–Z of the background and application knowledge of ocean engineering for use by ocean scientists and ocean engineers as well as nonspecialists such as engineers and scientists from all disciplines, economists, students, and politicians. Ocean engineering theories, ocean devices and equipment, ocean design and operation technologies are described by international experts, many from industry and each entry offers an introduction and references for further study, making current technology and operating practices available for future generations to learn from. The book also furthers our understanding of the current state of the art, leading to new and more efficient technologies with breakthroughs from new theory and materials. As the land resources approach the exploitation limit, ocean resources are becoming the next choice for the sustainable development. As such, ocean engineering is vital in the 21st century.
Passive Control Of Vortex Shedding In The Wakes Of Bluff Bodies
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Author : John Clifford Owen
language : en
Publisher:
Release Date : 2001
Passive Control Of Vortex Shedding In The Wakes Of Bluff Bodies written by John Clifford Owen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Experimental Investigation Of Active Control Of Bluff Body Vortex Shedding
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Author : Ilteris Koc
language : en
Publisher:
Release Date : 2008
Experimental Investigation Of Active Control Of Bluff Body Vortex Shedding written by Ilteris Koc and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Base flow (Aerodynamics) categories.
Three Dimensional Aspects Of Nominally 2 D And 3 D Bluff Body Wakes
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Author :
language : en
Publisher:
Release Date : 1995
Three Dimensional Aspects Of Nominally 2 D And 3 D Bluff Body Wakes written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1995 with categories.
Over the last decade, there has been much work carried out to understand three-dimensional effects at low Reynolds numbers (Re) in the wake of bluff bodies, yielding the reaction that end effects can influence the vortex shedding across large spanwise lengths. Wake patterns such as parallel shedding, oblique shedding, cellular shedding, transient patterns, such as 'phase shocks' and 'phase expansions', as well as the existence of large-scale 'vortex dislocations', have been investigated, aspects of this research being spearheaded by me studies at Cornell under the above Contract. In particular, we have discovered a new mechanism for oblique wave resonance in the far wake. We have found a means to control the near wake by using suction at the spanwise ends of a body, which has enabled much more precise phenomena to be investigated including the critical conditions for turbulence inception, and a careful study of 3-D wake transition. We have combined our research at Cornell with studies by Dr. Peter Monkewitz at Ecole Polytechnique, Lausanne, who has effectively laid much of the foundation of the description of these near wake patterns in terms of a Guinzburg-Landau equation. For example, the now transient phenomenon known as a 'phase expansion' has been found to be directly analogous to a Prandtl-Meyer expansion found in gas dynamics. Clearly, the work under the support of the ONR has led to a surprisingly rich new understanding of three-dimensional effects in nominally two-dimensional wake flows.
Control Of Two And Three Dimensional Wake Instabilities From Bluff Bodies
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Author :
language : en
Publisher:
Release Date : 1995
Control Of Two And Three Dimensional Wake Instabilities From Bluff Bodies written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1995 with categories.
The detailed, instantaneous flow structure of the near-wake of a cylinder subjected to various classes of active (open-loop) and passive control has been characterized using both qualitative flow visualization and high-image-density particle image velocimetry (piv) developed in our laboratories. The first cinema PIV system allows acquisition of images that are highly resolved in both space and time. Concepts of timing of vortex formation, period-doubled patterns of vortices, and modulated and phase-locked systems of vortices are addressed for controlled oscillations of the cylinder. Three-dimensional patterns of instantaneous vorticity allow classification of the modes of response of the near-wake, providing a basis for formulating concepts for attenuation of vortex formation.
Investigation Of Unsteady Three Dimensional Characteristics Of The Vortex Shedding Behind Bluff Bodies At Sub Critical Reynolds Numbers
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Author : 杜榮國
language : en
Publisher:
Release Date : 2007
Investigation Of Unsteady Three Dimensional Characteristics Of The Vortex Shedding Behind Bluff Bodies At Sub Critical Reynolds Numbers written by 杜榮國 and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.