Download or read book Experimental Investigations Into Vortex Rings in Pulsed Jets written by Erdoğan Aydemir and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 A Computational Investigation of Impulsive and Pulsed Starting Annular Jets written by Emad Abdel-Raouf and published by . This book was released on 2011 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computational study is carried out on low Reynolds number impulsive and pulsating annular jets. This work is inspired by the biological flow of marine life that uses jet propulsion for self maneuver. Marine life such as squids and jellyfish propel themselves by discharging a water jet followed by a refilling phase. The discharging portion is a starting jet, i.e. the releasing of a moving fluid into a quiescent fluid, while the refilling phase can be viewed as an inflow jet. The combined jets will be called fully oscillating jets. Although fully oscillating jets have been indirectly examined experimentally, they have never been studied computationally. This dissertation is divided into three investigations that examine the starting jet, inflow jet, and fully oscillating jet based on the resultant force (i.e. either thrust or suction force) at the annulus exit plane, jet efficiency, and vortex dynamics. Furthermore, each of the following three performance criterion is examined under various velocity imposed boundaries (i.e. impulsive, unit pulsed, and sinusoidal pulsed jets), ambient pressure, and blocking ratios. An axisymmetric, incompressible and unsteady Navier Stokes numerical model was used to implement the analysis. The model was validated against theoretical and experimental results, where both result types bounded the computational results of this endeavor. In addition, numerical verification was carried out on each of the three investigations ensuring grid and time independent results. Several substantial outcomes were drawn from the results of the three investigations. The numerical results confirmed previously published experimental data regarding the universal dimensionless time scale (i.e. vortex formation number) of optimal vortex ring development triggered by starting jets. Moreover, the computational results showed evidence that the vortex formation number was not affected by ambient pressure nor blocking ratio. The computational results also confirmed earlier experimental findings that pulsed jet inflows trigger a standing vortex ring. Furthermore, the current study showed that impulsive jet inflows do not trigger vortex ring formation. In addition, unlike the expected net thrust of zero due to mass flux, fully oscillating jets showed evidence of thrust augmentation due to the enhanced entrainment caused by the vortex formation.
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 Investigation of Viscous Vortex Rings and Zero net mass flux Jets written by John Edward Cater and published by . This book was released on 2002 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Series of Experimental Investigations Into Different Manifestations of the Vortex Ring State written by David Jonathan Pickles and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Laminar and Turbulent Vortex Rings in Air written by Dirse W. Sallet and published by . This book was released on 1974 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Developments in Theoretical and Experimental Fluid Mechanics written by U. Müller and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 663 pages. Available in PDF, EPUB and Kindle. Book excerpt: Dedicated to Prof. Dr.-Ing. J. Zierep
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 An Experimental Investigation of the Ground Vortex Created by a Moving Jet written by and published by . This book was released on 1989 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Vortex Pairing in a Circular Jet Under Controlled Excitation written by Khairul B. M. Quamruzzaman and published by . This book was released on 1978 with total page 736 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Heavy Vortex rings in Homogenous Surroundings written by Oddvar Frydenlund and published by . This book was released on 1972 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Study of Fusion of Vortex Rings written by Paul Russell Schatzle and published by . This book was released on 1987 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Simple Model of Pulsed Ejector Thrust Augmentation written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-29 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: A simple model of thrust augmentation from a pulsed source is described. In the model it is assumed that the flow into the ejector is quasi-steady, and can be calculated using potential flow techniques. The velocity of the flow is related to the speed of the starting vortex ring formed by the jet. The vortex ring properties are obtained from the slug model, knowing the jet diameter, speed and slug length. The model, when combined with experimental results, predicts an optimum ejector radius for thrust augmentation. Data on pulsed ejector performance for comparison with the model was obtained using a shrouded Hartmann-Sprenger tube as the pulsed jet source. A statistical experiment, in which ejector length, diameter, and nose radius were independent parameters, was performed at four different frequencies. These frequencies corresponded to four different slug length to diameter ratios, two below cut-off, and two above. Comparison of the model with the experimental data showed reasonable agreement. Maximum pulsed thrust augmentation is shown to occur for a pulsed source with slug length to diameter ratio equal to the cut-off value.Wilson, Jack and Deloof, Richard L. (Technical Monitor)Glenn Research CenterTHRUST AUGMENTATION; MATHEMATICAL MODELS; FLOW VELOCITY; HARTMANN-SPRENGER TUBES; VORTEX RINGS; PULSED JET ENGINES; EJECTORS...
Download or read book Experimental Investigation of Radial inflow Vortexes in Jet injection and Rotating peripheral wall Water Vortex Tubes written by Arthur Travers and published by . This book was released on 1968 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthetic Jets written by Kamran Mohseni and published by CRC Press. This book was released on 2014-09-17 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compiles Information from a Multitude of SourcesSynthetic jets have been used in numerous applications, and are part of an emergent field. Accumulating information from hundreds of journal articles and conference papers, Synthetic Jets: Fundamentals and Applications brings together in one book the fundamentals and applications of fluidic actuators.
Download or read book Experimental Studies of Colliding Vortex Rings in Air written by Raghothama Cauligi and published by . This book was released on 1983 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:
