Download or read book Some Experimental Studies of Vortex Rings Generated at Tube and Orifice Openings Using Particle Image Velocimetry written by T. T. Lim and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Fluid Vortices written by Sheldon Green and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 905 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fluid Vortices is a comprehensive, up-to-date, research-level overview covering all salient flows in which fluid vortices play a significant role. The various chapters have been written by specialists from North America, Europe and Asia, making for unsurpassed depth and breadth of coverage. Topics addressed include fundamental vortex flows (mixing layer vortices, vortex rings, wake vortices, vortex stability, etc.), industrial and environmental vortex flows (aero-propulsion system vortices, vortex-structure interaction, atmospheric vortices, computational methods with vortices, etc.), and multiphase vortex flows (free-surface effects, vortex cavitation, and bubble and particle interactions with vortices). The book can also be recommended as an advanced graduate-level supplementary textbook. The first nine chapters of the book are suitable for a one-term course; chapters 10--19 form the basis for a second one-term course.
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 Progress in Turbulence III written by Joachim Peinke and published by Springer Science & Business Media. This book was released on 2009-12-28 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: This third issue on “progress in turbulence” is based on the third ITI conference (ITI interdisciplinary turbulence initiative), which took place in Bertinoro, North Italy. Researchers from the engineering and physical sciences gathered to present latest results on the rather notorious difficult and essentially unsolved problem of turbulence. This challenge is driving us in doing basic as well as applied research. Clear progress can be seen from these contributions in different aspects. New - phisticated methods achieve more and more insights into the underlying compl- ity of turbulence. The increasing power of computational methods allows studying flows in more details. Increasing demands of high precision large turbulence - periments become aware. In further applications turbulence seem to play a central issue. As such a new field this time the impact of turbulence on the wind energy conversion process has been chosen. Beside all progress our ability to numerically calculate high Reynolds number turbulent flows from Navier-Stokes equations at high precision, say the drag co- ficient of an airfoil below one percent, is rather limited, not to speak of our lack of knowledge to compute this analytically from first principles. This is rather - markable since the fundamental equations of fluid flow, the Navier-Stokes eq- tions, have been known for more than 150 years.
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 An Experimental Study of Turbulent Vortex Rings Using Particle Image Velocimetry written by L. Gan and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Rings Generated by a Shrouded Hartmann Sprenger Tube written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-24 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: The pulsed flow emitted from a shrouded Hartmann-Sprenger tube was sampled with high-frequency pressure transducers and with laser particle imaging velocimetry, and found to consist of a train of vortices. Thrust and mass flow were also monitored using a thrust plate and orifice, respectively. The tube and shroud lengths were altered to give four different operating frequencies. From the data, the radius, velocity, and circulation of the vortex rings was obtained. Each frequency corresponded to a different length to diameter ratio of the pulse of air leaving the driver shroud. Two of the frequencies had length to diameter ratios below the formation number, and two above. The formation number is the value of length to diameter ratio below which the pulse converts to a vortex ring only, and above which the pulse becomes a vortex ring plus a trailing jet. A modified version of the slug model of vortex ring formation was used to compare the observations with calculated values. Because the flow exit area is an annulus, vorticity is shed at both the inner and outer edge of the jet. This results in a reduced circulation compared with the value calculated from slug theory accounting only for the outer edge. If the value of circulation obtained from laser particle imaging velocimetry is used in the slug model calculation of vortex ring velocity, the agreement is quite good. The vortex ring radius, which does not depend on the circulation, agrees well with predictions from the slug model. DeLoof, Richard L. (Technical Monitor) and Wilson, Jack Glenn Research Center NASA/CR-2005-213576, AIAA Paper 2005-5163, E-15041-2
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1995 with total page 488 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 An Experimental Study on the Interaction of Coaxial and Co rotating Vortex Rings written by Jagannadha Reddy Satti and published by . This book was released on 2012 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study investigated the role of formation time, Reynolds Number, and non-dimensional frequency number, the three most significant parameters in the dynamics of vortex rings, in the interaction between co-axial and co-rotating vortex rings and in the ring behaviors of merging and leapfrogging. To generate and investigate vortex rings with the required characteristics, two laminar vortex rings were generated consecutively from a piston-cylinder apparatus such that the rings propagated in the same direction and that the spatial separation between them decreased until they began merging. Using digital particle image velocimetry to measure the flow fields as well as the trajectory and circulation of the individual rings, a series of experiments were conducted at three formation times, with the experiments at each formation time repeated at different Reynolds Numbers, and the experiments at each Reynolds Number in turn repeated at different non-dimensional frequency numbers. The results indicate that at low Reynolds Numbers, the total circulation in the flow is relatively constant before and after the rings merge. However, at high Reynolds Numbers, the total circulation begins rapidly decreasing upon the contact of two vortex ring cores, indicating a transition to a turbulent vortex ring during merging, before stabilizing at a lower level, indicating that the merged ring has transitioned back to a laminar vortex ring after shedding some circulation.
Download or read book Kinematics and Dynamics of Vortex Rings in a Tube written by James G. Brasseur and published by . This book was released on 1979 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Combined Experimental and Numerical Investigations of a Vortex Ring Impinging Normally on a Wall written by Dražen Fabris and published by . This book was released on 1996 with total page 418 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental Observations of Vortex Ring Interaction with the Fluid Adjacent to a Surface written by A. W. Cerra and published by . This book was released on 1983 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental studies examined the breakdown of initially laminar vortex rings during impact with both solid and free surfaces in a quiescent environment, and with a solid surface beneath a developing laminar boundary layer. Flow interactions were visualized in water using dye and hydrogen-bubble techniques and recorded with a high-speed video system. When a vortex ring approaches a surface the resulting flow interaction appears to be chaotic and turbulent, but is actually a very organized viscid-inviscid process which rapidly disperses the vorticity of the vortex ring throughout the surrounding fluid. Described is the flow interaction which integrates the following phenomena: (1) generation of secondary vorticity of opposite sense to that of the vortex ring; (2) deviations in the trajectory of the vortex ring from that predicted by classical theory; and (3) the processes of organized dispersal of vorticity. The process by which vorticity dispersal occurs is dependent upon the initial Reynolds number (Re sub 0) of the vortex ring. For very weak rings, i.e. Re sub o less than 350, vorticity is dispersed by laminar diffusion. For stronger rings, vorticity dispersal occurs discretely through formation of secondary and tertiary vortex rings (SVR and TVR) via a viscous boundary layer process. Vorticity dispersal continues as a result of Biot-Savart-type interactions of the SVR and TVR with the original or primary vortex ring. During this interaction the diameter of the SVR is compressed, causing an instability in the SVR which is characterized by an azimuthal waviness.
Download or read book THE INTERACTION OF A VORTEX RING WITH A CONTAMINATED FREE SURFACE written by NICHOLAS JAMES KACHMAN and published by . This book was released on 1991 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: For W $\leq$ 5, the evolution of the flow near the surface was the same. For 10 $$ W $
Download or read book Vortex Ring Interaction with Liquid Interfaces written by Pepi Maksimovic and published by . This book was released on 1997 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vortex Ring Models written by Ionut Danaila and published by Springer. This book was released on 2022-04-17 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.
