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| Author | : Daniel L. Marcus |
| Publisher | : |
| Total Pages | : |
| Release | : 1991 |
| Genre | : |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 18 |
| Release | : 1990 |
| Genre | : |
| ISBN | : |
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.
| Author | : Faical Tounsi |
| Publisher | : |
| Total Pages | : 272 |
| Release | : 1995 |
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| Author | : Egon Krause |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 496 |
| Release | : 1998 |
| Genre | : Science |
| ISBN | : |
This text records the proceedings of the IUTAM Symposium held in Aachen in 1997. It reviews theories based on asymptotic expansions and gives an insight into new computational methods. Some applications of these methods demonstrate their capability, for example the analysis of core structures with axial variation, the description of the interaction of filaments with a solid body and of sound generation by vortex rings, the theoretical approach to the reduction of drag by manipulating vortex structures in shear layers, the numerical simulation of merging vortex rings and of bubble-type vortex breakdown in a tube, and investigations of vortex flows in aircraft and helicopter applications. The articles comprise a wide variety of fundamental investigations and of advanced engineering applications. The book summarizes the state of the art and also communicates recent results of specific flow problems. It addresses the large readership experienced in the field of vortex dynamics.
| Author | : Sheldon Green |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 905 |
| Release | : 2012-12-06 |
| Genre | : Technology & Engineering |
| ISBN | : 940110249X |
Fluid Vortices is a comprehensive, up-to-date, research-level overview covering all salient flows in which fluid vortices play a significant role. The various chapters have been written by specialists from North America, Europe and Asia, making for unsurpassed depth and breadth of coverage. Topics addressed include fundamental vortex flows (mixing layer vortices, vortex rings, wake vortices, vortex stability, etc.), industrial and environmental vortex flows (aero-propulsion system vortices, vortex-structure interaction, atmospheric vortices, computational methods with vortices, etc.), and multiphase vortex flows (free-surface effects, vortex cavitation, and bubble and particle interactions with vortices). The book can also be recommended as an advanced graduate-level supplementary textbook. The first nine chapters of the book are suitable for a one-term course; chapters 10--19 form the basis for a second one-term course.
| Author | : |
| Publisher | : |
| Total Pages | : 704 |
| Release | : 1995 |
| Genre | : Aeronautics |
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| Author | : H. L. Chen |
| Publisher | : |
| Total Pages | : 68 |
| Release | : 1991 |
| Genre | : Vortex motion |
| ISBN | : |
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.
| Author | : |
| Publisher | : |
| Total Pages | : 400 |
| Release | : 1948 |
| Genre | : Mechanics, Applied |
| ISBN | : |
| Author | : Pepi Maksimovic |
| Publisher | : |
| Total Pages | : 376 |
| Release | : 1997 |
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| ISBN | : |
| Author | : National Aeronautics and Space Administration (NASA) |
| Publisher | : Createspace Independent Publishing Platform |
| Total Pages | : 170 |
| Release | : 2018-07-17 |
| Genre | : |
| ISBN | : 9781722905439 |
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...
