A Numerical Study Of Viscous Vortex Rings Using A Spectral Method
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A Numerical Study Of Viscous Vortex Rings Using A Spectral Method
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Author : National Aeronautics and Space Administration (NASA)
language : en
Publisher: Createspace Independent Publishing Platform
Release Date : 2018-07-17
A Numerical Study Of Viscous Vortex Rings Using A Spectral Method written by National Aeronautics and Space Administration (NASA) and has been published by Createspace Independent Publishing Platform this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-07-17 with categories.
Viscous, axisymmetric vortex rings are investigated numerically by solving the incompressible Navier-Stokes equations using a spectral method designed for this type of flow. The results presented are axisymmetric, but the method is developed to be naturally extended to three dimensions. The spectral method relies on divergence-free basis functions. The basis functions are formed in spherical coordinates using Vector Spherical Harmonics in the angular directions, and Jacobi polynomials together with a mapping in the radial direction. Simulations are performed of a single ring over a wide range of Reynolds numbers (Re approximately equal gamma/nu), 0.001 less than or equal to 1000, and of two interacting rings. At large times, regardless of the early history of the vortex ring, it is observed that the flow approaches a Stokes solution that depends only on the total hydrodynamic impulse, which is conserved for all time. At small times, from an infinitely thin ring, the propagation speeds of vortex rings of varying Re are computed and comparisons are made with the asymptotic theory by Saffman. The results are in agreement with the theory; furthermore, the error is found to be smaller than Saffman's own estimate by a factor square root ((nu x t)/R squared) (at least for Re=0). The error also decreases with increasing Re at fixed core-to-ring radius ratio, and appears to be independent of Re as Re approaches infinity). Following a single ring, with Re=500, the vorticity contours indicate shedding of vorticity into the wake and a settling of an initially circular core to a more elliptical shape, similar to Norbury's steady inviscid vortices. Finally, we consider the case of leapfrogging vortex rings with Re=1000. The results show severe straining of the inner vortex core in the first pass and merging of the two cores during the second pass. Stanaway, S. K. and Cantwell, B. J. and Spalart, Philippe R. Ames Research Center COMPUTATIONAL FLUID DYNAMICS; NAVIER-STOKES EQUATION...
A Numerical Study Of Viscous Vortex Rings Using A Spectral Method
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Author : Sharon K. Stanaway
language : en
Publisher:
Release Date : 1988
A Numerical Study Of Viscous Vortex Rings Using A Spectral Method written by Sharon K. Stanaway and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1988 with Eddies categories.
Numerical Simulation Of A Viscous Vortex Ring Interaction With A Density Interface
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Author :
language : en
Publisher:
Release Date : 1990
Numerical Simulation Of A Viscous Vortex Ring Interaction With A Density Interface written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1990 with categories.
When a vortex-dominated flow interacts with a sharp density interface, the dynamics are characterized by the interaction of baroclinically generated vorticity with the already existing vorticity field. This can be seen in many natural and technology settings; examples are the interaction of a ship or submarine wake with a thermocline, the collision of a buoyant thermal with a temperature inversion, and the interaction of a vortex flow with a flame front. This problem also serves as a generic model for turbulent mixing and entrainment processes across sharp density interfaces. The interaction between vortices and a free surface, with corresponds to the case where the density jump is very large, has been studied fairly extensively, both experimentally and computationally. By comparison, the literature for the more general case of vortex pairs and rings interacting with sharp density interfaces is relatively sparse. Experiments and numerical studies have been performed, but the numerical simulations were confined primarily to vortex pairs, restricted to the inviscid case, and the effect of density variation modeled under the Boussinesq approximation. The experiments were also confined to the Boussinesq regime. In this paper, we study the motion of a vortex ring in a sharply stratified, viscous fluid via a numerical solution of the full Navier-Stokes equations with finite-amplitude density variation. both Boussinesq and non-Boussinesq flow regimes will be studied, the effect of viscosity on the interaction will be examined, and three-dimensional aspects of the motion will be addressed, such as Widnall instability of the vortex ring and vortex reconnection at the interface.
Vortex Flows And Related Numerical Methods
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Author : J.T. Beale
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-04-18
Vortex Flows And Related Numerical Methods written by J.T. Beale and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-04-18 with Technology & Engineering categories.
Many important phenomena in fluid motion are evident in vortex flow, i.e., flows in which vortical structures are significant in determining the whole flow. This book, which consists of lectures given at a NATO ARW held in Grenoble (France) in June 1992, provides an up-to-date account of current research in the study of these phenomena by means of numerical methods and mathematical modelling. Such methods include Eulerian methods (finite difference, spectral and wavelet methods) as well as Lagrangian methods (contour dynamics, vortex methods) and are used to study such topics as 2- or 3-dimensional turbulence, vorticity generation by solid bodies, shear layers and vortex sheets, and vortex reconnection. For researchers and graduate students in computational fluid dynamics, numerical analysis, and applied mathematics.
Vortex Methods
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Author : Georges-Henri Cottet
language : en
Publisher: Cambridge University Press
Release Date : 2008-04-24
Vortex Methods written by Georges-Henri Cottet and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008-04-24 with Science categories.
Vortex methods have matured in recent years, offering an interesting alternative to finite difference and spectral methods for high resolution numerical solutions of the Navier Stokes equations. In the past three decades, research into the numerical analysis aspects of vortex methods has provided a solid mathematical background for understanding the accuracy and stability of the method. At the same time vortex methods retain their appealing physical character, which was the motivation for their introduction. This book presents and analyzes vortex methods as a tool for the direct numerical simulation of impressible viscous flows. It will interest graduate students and researchers in numerical analysis and fluid mechanics and also serve as an ideal textbook for courses in fluid dynamics.
Full Simulation Of A Vortex Ring
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Author : Stanford University. Department of Aeronautics and Astronautics
language : en
Publisher:
Release Date : 1986
Full Simulation Of A Vortex Ring written by Stanford University. Department of Aeronautics and Astronautics and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1986 with categories.
Numerical Simulation Of A Viscous Vortex Ring Interaction With A Density Interface
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Author : Daniel L. Marcus
language : en
Publisher:
Release Date : 1991
Numerical Simulation Of A Viscous Vortex Ring Interaction With A Density Interface written by Daniel L. Marcus and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with categories.
Numerical Study On Cut And Connect Of Three Dimensional Vortex Tubes
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Author : H. L. Chen
language : en
Publisher:
Release Date : 1991
Numerical Study On Cut And Connect Of Three Dimensional Vortex Tubes written by H. L. Chen and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1991 with Vortex motion categories.
In the present study, generation of two vortex rings and their cut-and-connect process were numerically simulated by solving three-dimensional and time-dependent Navier-Stokes equations, under conditions similar to the laboratory experiment. In order to explain the mechanism of cut-and-connect, velocity, vorticity, pressure, helicity density and energy dissipation were examined for the flow field of the cut-and-connect of vortex rings. The present study revealed that energy dissipation is an essential process for circulation cancellation during vortex tubes cutting. Based on this energy dissipation mechanism, it is concluded that the cut-and-connect of vortex tubes may occur in the limit of inviscid flows. This conclusion is particularly important to the three-dimensional discrete vortex method for computing high Reynolds number flows. Features of helicity in the three-dimensional flow field of cut-and-connect process of vortex tubes were also investigated. The relation between the helicity density and the energy dissipation function in the three-dimensional flow field was examined.
Scientific And Technical Aerospace Reports
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Author :
language : en
Publisher:
Release Date : 1995
Scientific And Technical Aerospace Reports written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1995 with Aeronautics categories.
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Droplets And Sprays
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Author : Sergei Sazhin
language : en
Publisher: Springer
Release Date : 2014-05-19
Droplets And Sprays written by Sergei Sazhin and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-05-19 with Technology & Engineering categories.
Providing a clear and systematic description of droplets and spray dynamic models, this book maximises reader insight into the underlying physics of the processes involved, outlines the development of new physical and mathematical models and broadens understanding of interactions between the complex physical processes which take place in sprays. Complementing approaches based on the direct application of computational fluid dynamics (CFD), Droplets and Sprays treats both theoretical and practical aspects of internal combustion engine process such as the direct injection of liquid fuel, subcritical heating and evaporation. Including case studies that illustrate the approaches relevance to automotive applications, it is also anticipated that the described models can find use in other areas such as in medicine and environmental science.