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Author : Anatol Roshko
Publisher :
ISBN 13 :
Total Pages : 13 pages
Book Rating : 4.:/5 (227 download)
Download or read book Research on Bluff Body Vortex Wakes written by Anatol Roshko and published by . This book was released on 1993 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : National Research Council
Publisher : National Academies Press
ISBN 13 : 0309058791
Total Pages : 1100 pages
Book Rating : 4.3/5 (9 download)
Download or read book Twenty-First Symposium on Naval Hydrodynamics written by National Research Council and published by National Academies Press. This book was released on 1997-09-11 with total page 1100 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 6 pages
Book Rating : 4.:/5 (227 download)
Download or read book Vortex Shedding and Vortex Wakes: Dynamics, Instabilities and Modifications written by and published by . This book was released on 1994 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: RESEARCH OBJECTIVES: To study nonlinear and secondary instability properties of wake flows behind bluff bodies and their control and modification. (KAR) p. 2.
Author : Andre Sirilutporn Chan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (821 download)
Download or read book Control and Suppression of Laminar Vortex Shedding Off Two-dimensional Bluff Bodies written by Andre Sirilutporn Chan and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Author : Rafiuddin Azman
Publisher :
ISBN 13 :
Total Pages : 51 pages
Book Rating : 4.:/5 (953 download)
Download or read book Study of Vortex Shedding Around Bluff Body Using Air Flow Test Rig written by Rafiuddin Azman and published by . This book was released on 2008 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : International Union of Theoretical and Applied Mechanics
Publisher :
ISBN 13 :
Total Pages : 295 pages
Book Rating : 4.:/5 (248 download)
Download or read book Special Issue on Bluff Body Wakes and Vortex-induced Vibrations written by International Union of Theoretical and Applied Mechanics and published by . This book was released on 2001 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : E. Von Lavante
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Effects of Distrubed Inflow on Vortex-shedding from a Bluff Body written by E. Von Lavante and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : John Clifford Owen
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (593 download)
Download or read book Passive Control of Vortex Shedding in the Wakes of Bluff Bodies written by John Clifford Owen and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Vijay Matheswaran
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (136 download)
Download or read book Vortex Induced Vibrations written by Vijay Matheswaran and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vortex shedding and Vortex Induced Vibrations (VIV) of bluff bodies is a fundamental problem in fluid mechanics. The ubiquity of vortex shedding and VIV in several engineering fields has meant that a significant amount of research has centered on this subject. Recent studies have focused on the extraction of energy from steady flow using bodies undergoing VIV. In this dissertation, a new model for flow around a circular cylinder called the Hybrid Potential Flow (HPF) model is presented. The HPF model incorporates potential flow methods, experimental data and von Karman’s representation of the vortex wake to construct a complete solution for flow around a circular cylinder in the sub-critical Reynolds number regime $300 \leq Re \leq 1.5 x 10^5).$ Shedding frequencies and forces due to vortex shedding are calculated and compared to published results. The HPF model is extended to other bluff body geometries using conformal mapping. A composition of Karman-Trefftz transformations and Fornberg’s method is used to construct a conformal map between the physical domain and the circle plane. The combination of the HPF model and conformal mapping can thus be used to quickly calculate vortex shedding behavior for various bluff bodies. Validation of theoretical results is done through experimental methods. A flow visualization technique to view the time-averaged wake behind bluff bodies is developed and presented. Wind tunnel tests are done to validate predicted shedding frequencies for various bluff body geometries. A proof-of-concept prototype of a device that extracts energy from steady flow using VIV is developed. Emphasis is laid on the device being of low cost and complexity. Finally, principal conclusions of this dissertation and recommendations for future work are presented.
Author : Thomas Leweke
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (495 download)
Download or read book Bluff Body Wakes and Vortex-induced Vibrations (BBVIV-5) written by Thomas Leweke and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 : 9780732622329
Total Pages : pages
Book Rating : 4.6/5 (223 download)
Download or read book Proceedings of the Conference on Bluff Body Wakes and Vortex-induced Vibrations written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Mustapha Hammache
Publisher :
ISBN 13 :
Total Pages : 202 pages
Book Rating : 4.:/5 (318 download)
Download or read book An Experimental Study of the Origin of Oblique Vortex Shedding from Two-dimensional Bluff Bodies written by Mustapha Hammache and published by . This book was released on 1990 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Zachary John Taylor
Publisher :
ISBN 13 :
Total Pages : 314 pages
Book Rating : 4.:/5 (16 download)
Download or read book Vortex Shedding from Elongated Bluff Bodies written by Zachary John Taylor and published by . This book was released on 2011 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt: As the spans of suspension bridges increase, the structures become inherently flexible. The flexibility of these structures, combined with the wind and particular aerodynamics, can lead to significant motions. From the collapse due to flutter of the Tacoma Narrows Bridge to the case of vortex-induced vibrations (VIV) of the Storebælt Bridge, it is evident that a better understanding of the aerodynamics of these geometries is necessary. The work herein is motivated by these two problems and is presented in two parts. In the first part, the focus is on the physical mechanisms of vortex shedding. It is shown that the wake formation for elongated bluff bodies is distinct from shorter bluff bodies due to the leading edge separating-reattaching flow. Pressure data are then used to propose a mechanism of competition between the flow at the leading and trailing edges rather than synchronization which occurs at low Reynolds numbers. Within the context of this framework, the wakes are orthogonally decomposed and it was discovered that new modes appear not previously observed for shorter bluff bodies. In Part II, a timeresolved Particle Image Velocimetry (PIV) system is developed. This system is used to capture both the high and low frequency dynamics of flutter due its uniquely long recording length. It is shown that, contrary to conventional understanding, the vortex shedding does not significantly change during flutter. Thus, the fact that these bodies shed vortices is only a secondary effect in relation to the flutter instability. There is a distinct contrast between flutter and VIV: the latter is known to be governed by the vortex shedding wake and it has been shown herein that the former is not. Regarding the problem of VIV, it is shown that the wakes of these bodies are formed due to interaction with the leading edge separating-reattaching flow. As the leading edge separation angle grows, it is shown to disturb the trailing edge vortex shedding altering many of the key parameters including fluctuating lift force and shedding frequency.
Author : Vibhav Durgesh
Publisher :
ISBN 13 : 9780549743125
Total Pages : 123 pages
Book Rating : 4.7/5 (431 download)
Download or read book Experimental Study of Near Wake Dynamics Associated with Bluff Body Base Drag Reduction written by Vibhav Durgesh and published by . This book was released on 2008 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: This investigation studies in detail the changes occurring in near wake dynamics associated with base drag reduction on bluff bodies achieved via boundary layer modification. A wedge model and a flat plate model are used to study bluff bodies over a range of Reynolds number of 0.8 x 10 6 -0.3 x 10 6 . The boundary layer on both these models is modified using fore-body surface roughness, by applying sand grains with a mean diameter of 2.2 mm to their fore-body surfaces. Particle Image Velocimetry (PIV) measurements, as well as simultaneous PIV and time-resolved base pressure measurements, are performed on these models in order to determine the near wake changes associated with base drag reduction. For the wedge model, the PIV measurements capture a downstream region of x/h = 0-1.5, whereas, for the flat plate model, the PIV measurements are performed at three different distances downstream, x/h = 0-7, 7-14 and 14-21. The PIV results are analyzed using Proper Orthogonal Decomposition (POD) in order to identify the changes in coherent structures associated with base drag reduction. It is observed from the POD results that, when there is a reduction in base drag, the vortex shedding in the near wake becomes more organized, its strength decreases, and the vortex convects faster. This result differs from those obtained in earlier studies, where base drag reduction is achieved by interrupting vortex shedding. In order to reconstruct near wake dynamics simultaneous PIV and time-resolved pressure measurements are used. Using Linear Stochastic Estimation (LSE)-POD technique, the cycle-to-cycle variation in vortex shedding is accurately captured. It is observed from the reconstruction that for the smooth test cases, the cycle-to-cycle variations in the vortex shedding are significantly higher, as compared to the rough test cases.
Author : A. E. Corlett
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book A Study of the Vortex Shedding from Bluff Bodies at Low Reynolds Numbers written by A. E. Corlett and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 4 pages
Book Rating : 4.:/5 (227 download)
Download or read book Three-Dimensional Aspects of Nominally 2-D and 3-D Bluff Body Wakes written by and published by . This book was released on 1995 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Author : Owen M. Griffin
Publisher :
ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.:/5 (227 download)
Download or read book Vortex Shedding from Stationary and Vibrating Bluff Bodies in a Shear Flow written by Owen M. Griffin and published by . This book was released on 1980 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: If a fluid is in relative motion past a stationary bluff, or unstreamlined, structure and the vortex shedding frequency approaches one of the natural frequencies of the structure, then resonant flow-induced oscillations of the structure can occur when the damping of the system is sufficiently low. These resonant oscillations are accompanied by a 'lock-on' or capture of the vortex shedding frequency by the vibration frequency over a range of flow speeds, and this lock-on effect causes the wake and the structure to oscillate in unison. The periodic lift and the mean drag forces are amplified as a result of the vibrations, and changes in these fluid forces are closely related to the changes that occur in the flow field in the near wake of the body. Many practical ocean and wind engineering situations involve lightly-damped structures that are located in flows of air or water that are nonuniform along the length of the structure. The primary difference between a uniform flow and a shear flow is the presence and added complexity, in a shear flow, of vorticity whose vector is normal to the plane of the flow. When the incident flow approaches the body this vorticity is turned into the flow direction and interacts with the vortices which are shed from the body into the wake.
