Compressible Vortex Rings and Their Interaction with Stationary Surfaces PDF Download
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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: 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: Raffaello Mariani
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
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: Ran An
Publisher:
ISBN:
Category :
Languages : en
Pages : 380
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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: HUGH F. KEEDY
Publisher:
ISBN:
Category :
Languages : en
Pages : 152
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Author: NICHOLAS JAMES KACHMAN
Publisher:
ISBN:
Category :
Languages : en
Pages : 472
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Book Description
For W $\leq$ 5, the evolution of the flow near the surface was the same. For 10 $$ W $
Author: Sir Joseph John Thomson
Publisher:
ISBN:
Category : Matter
Languages : en
Pages : 168
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Book Description
Author: D. G. Akhmetov
Publisher: Springer Science & Business Media
ISBN: 3642050166
Category : Technology & Engineering
Languages : en
Pages : 154
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Book Description
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.
Author: Rhett William Jefferies
Publisher:
ISBN: 9781423580218
Category : Leading edges (Aerodynamics)
Languages : en
Pages : 184
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Book Description
Six stages of vortex development along the lower surface were also defined, including splitting of the tip vortex. The development of the tip vortex in the first three stages was found to depend more on the incident flow field and the resulting flux of vorticity from the upper surface. In the latter three stages, development depended more upon the mutual interaction of the tip and surface vortices with the lower surface.
