An Experimental Study on the Interaction of Coaxial and Co-rotating Vortex Rings PDF Download
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Author: Jagannadha Reddy Satti
Publisher:
ISBN:
Category : Vortex-motion
Languages : en
Pages : 190
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Book Description
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.
Author: Jagannadha Reddy Satti
Publisher:
ISBN:
Category : Vortex-motion
Languages : en
Pages : 190
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Book Description
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.
Author: JUNG TAI KWON
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
angle is reduced.
Author: Daniel T. H. New
Publisher: Springer
ISBN: 9812873961
Category : Technology & Engineering
Languages : en
Pages : 241
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Book Description
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.
Author: JUNG TAI KWON
Publisher:
ISBN:
Category :
Languages : en
Pages : 144
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Book Description
angle is reduced.
Author: M. Konstantinov
Publisher:
ISBN:
Category :
Languages : en
Pages : 58
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Book Description
Author: A. W. Cerra
Publisher:
ISBN:
Category : Flow visualization
Languages : en
Pages : 356
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Book Description
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.
Author: Raffaello Mariani
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Experimental studies have been conducted on the topic of the interaction of compressiblevortex rings on stationary surfaces. Throughout the campaign experimentswere carried out at pressure ratios of ! 4, 8, and 12. In the classical set up of airas both the driver and driven gas, these corresponded to theoretical incident Machnumbers Ms of 1.34, 1.54, and 1.61.Experiments were conducted on vortex rings impinging on a stationary surfacelocated at three (increasing) distances (1.66, 3.33, and 5.00 inner diameters) fromthe shock tube exit and on a stationary surface at a set distance but at three anglesinclinations (75, 60, and 45deg at 3.33 inner diameters). Results of the impingementof a vortex ring on a stationary solid surface perpendicular to the flow showed asymmetrical impingement process. A boundary layer is generated over the surfacewith an associated increase in pressure. An increase in velocity due to the radialexpansion causes the pressure over the surface to decrease. This expansion leads tothe development of azimuthal wave instabilities along the core. Pressure was seen toincrease with an increase in incident Mach number value. The variation in distanceresulted in an increase in pressure with an increase in distance. This counter-intuitiveresult can be explained by the higher translational velocity at impingement, alongwith the absence of the initial radial expansion of the counter-rotating vortex rings. The variation in surface angle inclination introduced several degrees of asymmetry. One core of the vortex ring impinges first on the surface due to its closerproximity to it, while the other core is still free to propagate. This process generatesan asymmetric boundary layer over the surface, and a higher rate of stretching ofthe lower core, resulting in its dissipation. At higher incident Mach numbers, theembedded rearward facing shock is reflected and propagates perpendicularly to thesurface. At the inclination angles of 60 and 45deg, the counter-rotating vortex ringsare fully deflected upwards and orbit around the main vortex. This phenomenonresult in a significant difference in pressure distribution between the upper and lowersections of the surface.
Author:
Publisher:
ISBN:
Category : Mechanics, Applied
Languages : en
Pages : 542
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Book Description
Author: Mikhail Konstantinov
Publisher:
ISBN:
Category :
Languages : de
Pages : 58
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Book Description
Author: Kenneth George Picha
Publisher:
ISBN:
Category : Fluid dynamics
Languages : en
Pages : 450
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Book Description
