Download or read book Energetics of Vortex Ring Formation written by J. Z. Irdumsa and published by . This book was released on 1983 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper presents an experimental investigation comparing the mass and energy content of fully formed laminar vortex rings in air with that of the original pulse which generated them for a variety of initial and boundary conditions. In particular, the fractional entrainment of mass and the partition of initial energy between kinetic energy of translation and kinetic energy of rotation is studied. It is found that a large degree of control can be exercised for the determination of the vortex energetics, as well as its final configuration. A technique is presented which enables calculation of kinetic energy of rotation from movie sequences. The ratio of characteristic translational speed to characteristic rotational speed is shown to be a useful parameter for correlation of data. Data on vortex size and speed are presented using this correlation and it is seen that all data, regardless of initial and boundary conditions, fall on a single curve. A theoretical curve is derived and it is seen that the data compare well with it. (Author).

Download or read book Vortex Rings written by D. G. Akhmetov and published by Springer Science & Business Media. This book was released on 2009-11-24 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vortex flow is one of the fundamental types of fluid and gas motion. These flows are the most spectacular in the form of concentrated vortices, characterized by the localization of vorticity (curl of velocity) in bounded regions of a space, beyond which the vorticity is either absent or rapidly falls down to zero. Concentrated vortices are often observed in nature, exemplified by atmospheric cyclones, whirlwinds and tornados, oceanic vortices, whirlpools on a water s- face, and ring vortices caused by explosive outburst of volcanoes. In technical - vices concentrated vortices form when flow separates from sharp edges of flying vehicles and ships. Among these are vortices flowing off the ends of airplane wings, and intentionally generated vortices for intensification of burning in c- bustion chambers, vortices in cyclonic devices used for mixing or separation of impurities in fluids and gases. One such remarkable and frequent type of conc- trated vortices is a vortex ring which constitutes a vortex tube closed into a t- oidal ring moving in a surrounding fluid like an isolated body out of contact with solid boundaries of the flow region if such boundaries exist. Formation and motion of vortex rings are important part of the dynamics of a continuum medium and have been studied for more than a century.

Download or read book Vortex Ring Models written by Ionut Danaila and published by Springer Nature. This book was released on 2021-04-16 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a guide to understanding models of vortex rings, starting from classical ones (circular vortex filament, Hill and Norbury-Fraenkel inviscid models) to very recent models incorporating viscous effects and realistic shapes of the vortex core. Unconfined and confined viscous vortex rings are described by closed formulae for vorticity, stream function, translational velocity, energy, impulse and circulation. Models are applied to predict the formation number of optimal vortex rings and to describe two-phase vortex ring-like structures generated in internal combustion engines. The book provides a detailed presentation of analytical developments of models, backed up by illustrations and systematic comparisons with results of direct numerical simulations. The book is useful for graduate students in applied mathematics, engineering and physical sciences. It is a useful reference for researchers and practising engineers interested in modelling flows with vortex rings.

Download or read book Lagrangian Coherent Structures in Vortex Ring Formation written by Braxton N. Harter and published by . This book was released on 2019 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: The proposed limiting process in vortex ring formation is consistent with existing analytical descriptions of pinch-off; present findings reveal the physical phenomena that initialize the process. These insights provide a clear path forward for researchers to maximize vortex ring formation for the effective transport of mass, momentum, and energy in fluids.

Download or read book Formation of Orifice generated Vortex Rings written by Raphaël Limbourg and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this dissertation, the formation of vortex rings at the edge of orifices, as opposed to the well-studied nozzle geometry, is experimentally and theoretically investigated using time-resolved planar particle image velocimetry. This thesis builds upon the groundwork of Gharib et al. (1998) on optimal vortex formation and the general study of non-parallel starting jets initiated by Krieg & Mohseni (2013a).The orifice apparatus can be used to model complex geometries observed in nature, such as heart valves or squids' funnel, and constitutes the main equipment to produce synthetic jets and pulsed jets, which can be used for flow control, unsteady heat and mass transfer or thrust generation. Krieg & Mohseni (2013a) studied orifice starting jets and found that this apparatus produces more circulation, hydrodynamic impulse and kinetic energy than the equivalent nozzle geometry. The specific initial boundary conditions of the orifice geometry, namely the non-zero radial velocity at the exhaust, were shown to be responsible for the increased production of the invariants of the motion. Nevertheless, the ring quantities were not measured, as well as the "formation number", as originally defined by Gharib et al. (1998).An objective of the study is therefore to investigate the influence of initial conditions on the formation process of vortex rings and test the validity of the supposedly universal time scale that is the formation number. In particular, it is found that the sharp edge of the orifice destabilises the flow, forming a train of discrete vortices, as opposed to the continuous feeding shear layer observed in the case of nozzles. As such, it is shown that orifice-generated vortex rings do not reach their maximum circulation state at the same instant, and location, as their maximum impulse and energy states.Moreover, covering the exhaust of a tube with an orifice plate introduces an additional geometrical parameter, that is the orifice-to-tube diameter ratio. A parametric study is undertaken to assess the influence of this ratio on the production of the invariants of the motion, which are then related to vortex ring formation. Unsurprisingly, the classic slug-flow model is found to underestimate the rate of production of the invariants, and this for all orifice-to-tube diameter ratios, although in a lesser extent for the nozzle case. An extension to the model is proposed to account for the contraction the flow is experiencing when fluid is being pushed out through the orifice. The contraction coefficient found analytically by Von Mises (1917) for two-dimensional flows is applied to the present axisymmetric three-dimensional cases and the discrepancy with the measurements is reduced from a maximum of 130%, 50% and 120% to 10%, 10% and 25% for the circulation, the hydrodynamic impulse and the kinetic energy, respectivelyFinally, the critical non-dimensional numbers commonly used to characterise vortex ring formation are computed at the exhaust of the orifice geometry. Again, the classic slug-flow model is observed to poorly predict their evolution. It is shown that using the extended slug-flow model to redefine the non-dimensional time, usually referred as "formation time", allows one to collapse all cases, orifices and nozzle, onto a single curve. Hence, given the proposed scaling, a formation number of approximately 4 is found for straight nozzle, converging nozzle and orifice-generated vortex ringsIn conclusions, this thesis not only shows experimental evidence of the difference in the unsteady formation of vortex rings emanating from orifice geometries, but also provides a theoretical explanation and an analytical model which incorporates the unique physical phenomena of orifice starting jets and extends the well-accepted results of the literature, for instance the result of Gharib et al. (1998), to the formation of orifice-generated vortex rings"--

Download or read book Vortex Rings and Jets written by Daniel T. H. New and published by Springer. This book was released on 2015-03-26 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, recent developments in our understanding of fundamental vortex ring and jet dynamics will be discussed, with a view to shed light upon their near-field behaviour which underpins much of their far-field characteristics. The chapters provide up-to-date research findings by their respective experts and seek to link near-field flow physics of vortex ring and jet flows with end-applications in mind. Over the past decade, our knowledge on vortex ring and jet flows has grown by leaps and bounds, thanks to increasing use of high-fidelity, high-accuracy experimental techniques and numerical simulations. As such, we now have a much better appreciation and understanding on the initiation and near-field developments of vortex ring and jet flows under many varied initial and boundary conditions. Chapter 1 outlines the vortex ring pinch-off phenomenon and how it relates to the initial stages of jet formations and subsequent jet behaviour, while Chapter 2 takes a closer look at the behaviour resulting from vortex ring impingement upon solid boundaries and how the use of a porous surface alters the impingement process. Chapters 3 and 4 focus upon the formation of synthetic jets from vortex ring structures experimentally and numerically, the challenges in understanding the relationships between their generation parameters and how they can be utilized in flow separation control problems. Chapter 5 looks at the use of imposing selected nozzle trailing-edge modifications to effect changes upon the near-field dynamics associated with circular, noncircular and coaxial jets, with a view to control their mixing behaviour. And last but not least, Chapter 6 details the use of unique impinging jet configurations and how they may lend themselves towards greater understanding and operating efficacies in heat transfer problems. This book will be useful to postgraduate students and researchers alike who wish to get up to speed regarding the latest developments in vortex ring and jet flow behaviour and how their interesting flow dynamics may be put into good use in their intended applications.

Download or read book Origin and Dynamics of Vortex Rings in Drop Splashing written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A vortex is a flow phenomenon that is very commonly observed in nature. More than a century, a vortex ring that forms during drop splashing has caught the attention of many scientists due to its importance in understanding fluid mixing and mass transport processes. However, the origin of the vortices and their dynamics remain unclear, mostly due to the lack of appropriate visualization methods. Here, with ultrafast X-ray phase-contrast imaging, we show that the formation of vortex rings originates from the energy transfer by capillary waves generated at the moment of the drop impact. Interestingly, we find a row of vortex rings along the drop wall, as demonstrated by a phase diagram established here, with different power-law dependencies of the angular velocities on the Reynolds number. These results provide important insight that allows understanding and modelling any type of vortex rings in nature, beyond just vortex rings during drop splashing.

Download or read book Vortex Formation in the Cardiovascular System written by Arash Kheradvar and published by Springer Science & Business Media. This book was released on 2012-02-01 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vortex Formation in the Cardiovascular System will recapitulate the current knowledge about the vortex formation in the cardiovascular system, from mechanics to cardiology. This can facilitate the interaction between basic scientists and clinicians on the topic of the circulatory system. The book begins with a synopsis of the fundamentals aspects of fluid mechanics to give the reader the essential background to address the proceeding chapters. Then the fundamental elements of vortex dynamics will be discussed, explaining the conditions for their formation and the rules governing their dynamics. The main equations are accompanied by mathematical models. Cardiovascular vortex formation is first analyzed in physiological, healthy conditions in the heart chambers and in the large arterial vessels. The analysis is initially presented with an intuitive appeal grounded on the physical phenomena and a focus on its clinical significance.In the proceeding chapters, the knowledge gained from either clinical or basic science literature will be discussed. The corresponding mathematical elements will finally be presented to ensure the adequate diligence. The proceeding chapters ensue to the analysis of pathological conditions, when the reader may have developed the ability to recognize normal from abnormal vortex formation phenomenon. Pathological vortex formation represents vortices that develop at sites where normally laminar flow should exist, e.g. stenosis and aneurisms. This analysis naturally leads to the interaction of vortices due to the surgical procedures with respect to prediction of changes in vortex formation. The existing techniques, from medical imaging to numerical simulations, to explore vortex flows in the cardiovascular systems will also be described. The presentations are accompanied by the mathematical definitions can that be understandable for reader without the advanced mathematical background, while an interested reader with more advanced knowledge in mathematics can be referred to references for further quantitative analyses. The book pursues the objective to transfer the fundamental vortex formation phenomena with application to the cardiovascular system to the reader. This book will be a valuable support for physicians in the evaluation of vortex influence on diagnosis and therapeutic choices. At the same time, the book will provide the rigorous information for research scientists, either from medicine and mechanics, working on the cardiovascular circulation incurring with the physics of vortex dynamics.

Download or read book AFOSR Technical Report Summaries written by and published by . This book was released on 1984 with total page 452 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Treatise on the Motion of Vortex Rings written by Sir Joseph John Thomson and published by . This book was released on 1883 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1984 with total page 558 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Formation and Propagation of Vortex Rings in Axisymmetric Bounded Pulsed Flow written by Stanford University. Department of Aeronautics and Astronautics and published by . This book was released on 1976 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Drop Surface Interactions written by Martin Rein and published by Springer. This book was released on 2014-05-04 with total page 317 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive overview of fluid mechanical, thermal and physico-chemical aspects of drop-surface interactions. Basic physical mechanisms pertaining to free-surface flow phenomena characteristic of drop impact on solid and liquid surfaces are explained emphasizing the importance of scaling. Moreover, physico-chemical fundamentals relating to a forced spreading of complex solutions, analytical tools for calculating compressibility effects, and heat transfer and phase change phenomena occurring during solidification and evaporation processes, respectively, are introduced in detail. Finally, numerical approaches particularly suited for modeling drop-surface interactions are consisely surveyed with a particular emphasis on boundary integral methods and Navier-Stokes algorithms (volume of fluid, level set and front tracking algorithms). The book is closed by contributions to a workshop on Drop-Surface Interactions held at the International Centre of Mechanical Sciences.

Download or read book A Dynamical Systems Analysis of Vortex Pinch off written by Clara O'Farrell and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vortex rings constitute the main structure in the wakes of a wide class of swimming and flying animals, as well as in cardiac flows and in the jets generated by some moss and fungi. However, there is a physical limit, determined by an energy maximization principle called the Kelvin-Benjamin principle, to the size that axisymmetric vortex rings can achieve. The existence of this limit is known to lead to the separation of a growing vortex ring from the shear layer feeding it, a process known as `vortex pinch-off', and characterized by the dimensionless vortex formation number. The goal of this thesis is to improve our understanding of vortex pinch-off as it relates to biological propulsion, and to provide future researchers with tools to assist in identifying and predicting pinch-off in biological flows. To this end, we introduce a method for identifying pinch-off in starting jets using the Lagrangian coherent structures in the flow, and apply this criterion to an experimentally generated starting jet. Since most naturally occurring vortex rings are not circular, we extend the definition of the vortex formation number to include non-axisymmetric vortex rings, and find that the formation number for moderately non-axisymmetric vortices is similar to that of circular vortex rings. This suggests that naturally occurring vortex rings may be modeled as axisymmetric vortex rings. Therefore, we consider the perturbation response of the Norbury family of axisymmetric vortex rings. This family is chosen to model vortex rings of increasing thickness and circulation, and their response to prolate shape perturbations is simulated using contour dynamics. Finally, the response of more realistic models for vortex rings, constructed from experimental data using nested contours, to perturbations which resemble those encountered by forming vortices more closely, is simulated using contour dynamics. In both families of models, a change in response analogous to pinch-off is found as members of the family with progressively thicker cores are considered. We posit that this analogy may be exploited to understand and predict pinch-off in complex biological flows, where current methods are not applicable in practice, and criteria based on the properties of vortex rings alone are necessary.

Download or read book Vortex Ring Models written by Ionut Danaila and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a guide to understanding models of vortex rings, starting from classical ones (circular vortex filament, Hill and Norbury-Fraenkel inviscid models) to very recent models incorporating viscous effects and realistic shapes of the vortex core. Unconfined and confined viscous vortex rings are described by closed formulae for vorticity, stream function, translational velocity, energy, impulse and circulation. Models are applied to predict the formation number of optimal vortex rings and to describe two-phase vortex ring-like structures generated in internal combustion engines. The book provides a detailed presentation of analytical developments of models, backed up by illustrations and systematic comparisons with results of direct numerical simulations. The book is useful for graduate students in applied mathematics, engineering and physical sciences. It is a useful reference for researchers and practising engineers interested in modelling flows with vortex rings. .

Download or read book Energy Harvesting from a Vortex Ring Using Highly Deformable Smart Materials written by Jia Cheng Hu and published by . This book was released on 2015 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recently, the growing demand of compact energy harvesters for wireless sensor networks has lead to an increasing interest in exploring the energy harvesting capabilities of smart materials. Smart materials are a category of transducer that is able to convert dynamic structural deformations into electricity and vice versa. To investigate the feasibility and the potential of small-scale smart material-based harvesters to obtain energy from ambient fluid environments, interactions between a vortex ring and smart material structure are examined. Vortex rings are a class of coherent structure that is common in nature and act as a canonical representation of vortex structures. Herein, two energy harvesting configurations are considered. First, energy transfer from a passing vortex ring to a cantilevered plate, which is oriented parallel to and offset from the vortex ring's path, is modeled and optimized. The three-dimensional problem is simplified to a two-dimensional problem using a novel method that maintains the loading characteristics of the vortex ring. Two-dimensional Kirchhoff-Love plate theory and two-dimensional potential flow theory are utilized to represent the solid and fluid, respectively. The coupled fluid-structure model is solved simultaneously and validated against published experimental data. Employing this analytical model, the optimization study aims at locating the resonance frequency with respect to the change in fluid and structure parameters. The dimensionless resonance frequency is established as a specific ratio between the plate's fundamental frequency and vortex convective time-scale using a classical moving point load analysis. The result of the optimization study provides a description and empirical formulation of the shift in dimensionless frequency as a result of various fluid and structure parameter adjustments. In the second configuration, the energy harvesting potential of a vortex ring impacting an ionic polymer composite (IPMC) annulus is examined experimentally. The annulus is axis-symmetrically aligned with an incoming vortex ring that is generated by a piston/cylinder setup. The tip deflection of the annular energy harvester is measured with a laser displacement sensor, while the cross-sectional flow field is measured with particle imaging velocimetry and the electrical energy accumulated by the IPMC is estimated with the short-circuit current output. The experimental results unveiled that the annulus is first pulled by the vortex ring low pressure core, and then pushed upon impact. A secondary vortex ring is observed convecting away from the annulus. It is possibly formed out of the vortex induced vorticity at the annulus tip, while the incoming vortex ring is destroyed at impact. The experimental result is found to be in good agreement with an analytical solution.

Download or read book A New Model for Inviscid Vortex Ring Formation written by M. Shusser and published by . This book was released on 1999 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: