Download or read book A Preliminary Study of Vortex Formation from Pulsed Jets written by J. Z. Irdmusa and published by . This book was released on 1982 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is known that superior thrust augmentation may be obtained in ejectors by the use of pulsed jets as opposed to steady flow jets. Pulsed jets and other unsteady flow devices offer the advantage that they can capitalize on the reversible work of interface pressure forces as well as the usual irreversible turbulent mixing. The latter alone is employed in steady flow ejectors. When a pulsed jet discharges into a duct or an open environment, the jet forms a toroidal vortex ring which acts as a piston pushing the ambient fluid in its path. The configuration of this vortex ring can be extensively controlled by proper control of the boundary conditions at the exit of the jet. The present work is a preliminary study of the configurations of the vortex rings produced by different boundary conditions and of their subsequent behavior. It is hoped that such a study will illuminate some avenues of improvement for pulsed-jet ejector technology.
Download or read book Proceedings written by R. P. Braden and published by . This book was released on 1982 with total page 1094 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 40th AIAA Aerospace Sciences Meeting Exhibit written by and published by . This book was released on 2002 with total page 592 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Water R718 Turbo Compressor and Ejector Refrigeration Heat Pump Technology written by Milan N. Šarevski and published by Butterworth-Heinemann. This book was released on 2016-02-03 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water (R718) Turbo Compressor and Ejector Refrigeration/Heat Pump Technology provides the latest information on efficiency improvements, a main topic in recent investigations of thermal energy machines, plants, and systems that include turbo compressors, ejectors, and refrigeration/heat pump systems. This, when coupled with environmental concerns, has led to the application of eco-friendly refrigerants and to a renewed interest in natural refrigerants. Within this context, readers will find valuable information that explores refrigeration and heat pump systems using natural refrigerants, polygeneration systems, the energy efficiency of thermal systems, the utilization of low temperature waste heat, and cleaner production. The book also examines the technical, economic, and environmental reasons of R718 refrigeration/heat pump systems and how they are competitive with traditional systems, serving as a valuable reference for engineers who work in the design and construction of thermal plants and systems, and those who wish to specialize in the use of R718 as a refrigerant in these systems. Describes existing novel R718 turbo compressor and ejector refrigeration/heat pump systems and technologies Provides procedures calculating and optimizing cycles, system components, and system structures Estimates the performance characteristics of the thermal systems Exposes the possibilities for wider applications of R718 systems in the field of refrigeration and heat pumps
Download or read book Numerical Simulation of Vortex Generating Jets in Zero and Adverse Pressure Gradients written by Curtis Lynn Memory and published by . This book was released on 2007 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt: Numerical simulations of particle image velocimetry (PIV) experiments conducted with vortex generating jets (VGJs) on a flat plate, at a Reynolds number based on plate length of 50,000, were performed for three flow conditions using a time-accurate hybrid Navier-Stokes solver. Time-averaged steady blowing of angled jets, subjected to a zero pressure gradient, yielded excellent agreement with the PIV data in terms of vortex formation and strength. Observed flow features include primary and secondary vortices, where the primary vortex eventually dominates the downstream region. A shell wall structure, created by smaller vortical structures surrounding the developing vortices, was also observed. A pulsed jet in a zero pressure gradient was then initialized from a no-control case. A qualitative comparison between averaged experimental and instantaneous numerical results was performed with good agreement in terms of the convected size and distance of the wake. Analysis of the instantaneous numerical flow field agreed well with various flow visualization experiments describing the formation of "kidney" vortices. Various indicators point to the production of a primary vortex by the reduced mass flow of the pulsed jet. Finally, an adverse pressure gradient was applied, inducing a laminar separation zone on the plate. A pulsed angled jet induced strong spanwise vortices in the separated shear layer which appear to weaken the separation zone and allow the bulk jet fluid to flush the remaining low-momentum fluid out of the domain. It is reasonable to assume that reduced blowing ratios and duty cycles would produce similar shear layer vortices and comparable loss reductions. Influences of both turbulent transition and dominant vortical structures were observed, though the spanwise shear layer vortices appear to be critical to the laminar separation reduction scenarios observed in this study.
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 Mixing and Combustion of Pulsed Gas Jets written by and published by . This book was released on 1988 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Research in Progress written by and published by . This book was released on 1982 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Announcements Index written by and published by . This book was released on 1983-05 with total page 1200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Government Reports Annual Index written by and published by . This book was released on 1983 with total page 1168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sections 1-2. Keyword Index.--Section 3. Personal author index.--Section 4. Corporate author index.-- Section 5. Contract/grant number index, NTIS order/report number index 1-E.--Section 6. NTIS order/report number index F-Z.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2006 with total page 1380 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Internal flow mechanism of modern hydraulic machinery written by Kan Kan and published by Frontiers Media SA. This book was released on 2023-02-03 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dissertation Abstracts International written by and published by . This book was released on 2007 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Abstract Bulletin written by and published by . This book was released on with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Paper written by and published by . This book was released on 2000 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt:
