Download or read book Investigation of Three Dimensional Vortex Instability written by F. X. Wortmann and published by . This book was released on 1959 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report covers the development and construction of a laminar water tunnel designed for the investigation of a three-dimensional vortex instability of the laminar boundary layer on the concave wall. Both the assignment and the tellurium method have brought up problems for the solution of which entirely new approaches had to be found. Apart from the solution of a large variety of individual problems a rigid, porous, corrosion-resistant wall surface was developed for boundary layer suction.
Download or read book Investigation of Three dimensional Vortex Wake Interaction with the Ground written by Ihab G. Adam and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inviscid Vortex Motions in Weakly Three dimensional Boundary Layers and Their Relation with Instabilities in Stratified Shear Flows written by Institute for Computer Applications in Science and Engineering and published by . This book was released on 1992 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Studies of Vortex Dominated Flows written by M.Y. Hussaini and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 367 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the astrophysical scale of a swirling spiral galaxy, through the geophysical scale of a hurricane, down to the subatomic scale of elementary particles, vortical motion and vortex dynamics have played a profound role in our understanding of the physical world. Kuchemann referred to vortex dynamics as "the sinews and muscles of fluid motion. " In order to update our understanding of vortex dominated flows, NASA Langley Research Center and the Institute for Computer Applications in Science and Engineering (ICASE) conducted a workshop during July 9-11, 1985. The subject was broadly divided into five overlapping topics vortex dynamics, vortex breakdown, massive separation, vortex shedding from sharp leading edges and conically separated flows. Some of the experts in each of these areas were invited to provide an overview of the subject. This volume is the proceedings of the workshop and contains the latest, theoretical, numerical, and experimental work in the above-mentioned areas. Leibovich, Widnall, Moore and Sirovich discussed topics on the fundamentals of vortex dynamics, while Keller and Hafez treated the problem of vortex break down phenomena; the contributions of Smith, Davis and LeBalleur were in the area of massive separation and inviscid-viscous interactions, while those of Cheng, Hoeijmakers and Munnan dealt with sharp-leading-edge vortex flows; and Fiddes and Marconi represented the category of conical separated flows.
Download or read book Numerical Investigation of Three dimensional Vortex Breakdown written by Keith Vincent Lucas and published by . This book was released on 1997 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Progress in Turbulence VIII written by Ramis Örlü and published by Springer Nature. This book was released on 2019-08-27 with total page 339 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume collects the edited and reviewed contributions presented in the 8th iTi Conference on Turbulence, held in Bertinoro, Italy, in September 2018. In keeping with the spirit of the conference, the book was produced afterwards, so that the authors had the opportunity to incorporate comments and discussions raised during the event. The respective contributions, which address both fundamental and applied aspects of turbulence, have been structured according to the following main topics: I TheoryII Wall-bounded flowsIII Simulations and modellingIV ExperimentsV Miscellaneous topicsVI Wind energy/div
Download or read book Vortex Dynamics written by P. G. Saffman and published by Cambridge University Press. This book was released on 1995-02-24 with total page 332 pages. Available in PDF, EPUB and Kindle. Book excerpt: Vortex dynamics is a natural paradigm for the field of chaotic motion and modern dynamical system theory. However, this volume focuses on those aspects of fluid motion that are primarily controlled by the vorticity and are such that the effects of the other fluid properties are secondary.
Download or read book Three dimensional Vortex body Interaction in a Viscous Fluid written by Jeffrey S. Marshall and published by . This book was released on 1999 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental and computational study of the impact of a vortex with a body oriented normal to the vortex axis was performed. Particular focus was placed on understanding characteristics of the secondary vorticity ejected from the body and the interaction of the secondary vorticity with the primary vortex. Since both onset of boundary layer separation and the form of the secondary vorticity structures are sensitive to variation of the velocity normal to the body axis, the effect of normal velocity on vortex-body interaction was carefully examined. The physical features of the flow evolution were categorized in terms of an impact parameter and a thickness parameter, which respectively represent ratios of velocity and length scales associated with the vortex to those associated with the flow in the absence of the vortex. Experiments were performed using a combination of laser-induced fluorescence (LIF) flow visualization and particle-image velocimetry (PIV) in a water tank to examine the form of the secondary vorticity structures with both "high" and "low" values of the impact parameter for normal vortex interaction with a circular cylinder and with a thin blade. A new type of Lagrangian vorticity method based on a tetrahedral mesh was developed and applied to compute the secondary vorticity evolution during vortex-cylinder interaction. Computations were also performed for model problems to examine in detail wrapping of a vortex loop around a columnar vortex and impulsive cutting of a columnar vortex with finite axial flow.
Download or read book The G rtler Vortex Instability Mechanism in Three dimensional Boundary Layers written by Philip Hall and published by . This book was released on 1984 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Goertler Vortex Instability Mechanism in Three dimensional Boundary Layers written by Institute for Computer Applications in Science and Engineering and published by . This book was released on 1984 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Three Dimensional Vortex Interactions written by Valdis Kibens and published by . This book was released on 1988 with total page 35 pages. Available in PDF, EPUB and Kindle. Book excerpt: Three-dimensional vortex interactions were investigated in jets with slanted, indeterminate origin exit nozzles, and in mixing layers behind a splitter plate with a swept trailing edge. Flow visualization images were quantitatively processed to characterize complex three dimensional vortex interactions in non axisymmetric jets. Phase conditioned pulsed laser sheet illumination was used to obtain a series of sectional images while rotating the asymmetric nozzle. The sectional images were recombined into an unwrapped representation of the developing vortex systems in the shear layer. Partial pairing of sections of adjacent vortex systems was shown to be responsible for asymmetric shear layer growth. Flow visualization in the flow behind the swept trailing edge showed that two families of instability waves can develop with different orientations with respect to the trailing edge angle. Excitation was shown to enhance waves with orientation parallel to the trailing edge or perpendicular to the mean flow direction, depending on excitation frequency. Streamwise wavelengths of the two wave families were related by their angular separation. Keywords: Fluid mechanics; Shear layers; Jet flows; Passive control; Active control; Image processing; Control of turbulence; Asymmetric nozzles; Slanted nozzles; Indeterminate origin nozzles; Pulsed laser flow visualization; Mixing layers; Instability waves.
Download or read book Numerical Study on Cut and connect of Three Dimensional Vortex Tubes written by H. L. Chen and published by . This book was released on 1991 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Capitalizing on Convective Instabilities in a Streamwise Vortex wall Interaction written by Stuart Ira Benton and published by . This book was released on 2015 with total page 148 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Secondary flows in turbomachinery and similar engineering applications are often dominated by a single streamwise vortex structure. Investigations into the control of these flows using periodic forcing have shown a discrete range of forcing frequency where the vortex is particularly receptive. Forcing in this frequency range results in increased movement of the vortex and decreased total pressure losses. Based on the hypothesis that this occurs due to a linear instability associated with the Crow instability, a fundamental study of instabilities in streamwise vortex-wall interactions is performed. In the first part of this study a three-dimensional vortex-wall interaction is computed and analyzed for the presence of convective instabilities. It is shown that the Crow instability and a range of elliptic instabilities exist in a similar form as to what has been studied in counter-rotating vortex pairs. The Crow instability is particularly affected by the presence of a solid no-slip wall. Differences in the amplification rate, oscillation angle, Reynolds number sensitivity, and transient growth are each discussed. The spatial development of the vortex-wall interaction is shown to have a further stabilizing effect on the Crow instability due to a "lift-off" behavior. Despite these discoveries, it is still shown that amplitude growth on the order of 20% is possible and transient growth mechanisms might result in an order-of-magnitude of further growth if properly initiated. With these results in mind, an experiment is developed to isolate the streamwise vortex-wall interaction. Through the use of a vortex generating wing section and a suspended splitter plate, a stable interaction is created that agrees favorably in structure to the three-dimensional computations. A small synthetic jet actuator is mounted on the splitter plate below the vortex. Phase-locked stereo-PIV velocity data and surface pressure taps both show spatial amplification of the disturbance in a frequency range which agrees well with the prediction for the Crow instability. An analysis of the vortex response shows a primarily horizontal oscillation of the vortex column which strongly interacts with the secondary vortex structure that develops in the boundary layer.
Download or read book Theoretical and Experimental Investigations of Three dimensional Viscous Vortex Flows written by Coleman duP. Donaldson and published by . This book was released on 1963 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research efforts carried out at ARAP during the past five years in the field of viscous vortex motions are summarized. The work cited constitutes a rather extensive program of theo retical and experimental studies of vortex mo tions in general and of three-dimensional laminar and turbulent incompressible driven vortices in particular. The theoretical studies fall into three general categories; the first and most important comprising velocity distributions for steady laminar motion, the second dealing with unsteady velocity characteristics, and the third treating temperature distributions for the steady motions first considered. An evaluation and discussion of the effects of turbulence in real flows of the general type under consideration is included. The work performed and the results and conclusions reached in each of the areas of study already mentioned are discussed. (Author).
Download or read book Numerical Studies of Three dimensional Breakdown in Trailing Vortex Wakes written by and published by . This book was released on 1976 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fluid Vortices written by Sheldon Green and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 905 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Singularity Formation in Three dimensional Vortex Sheets written by Gang Hu and published by . This book was released on 2001 with total page 370 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, we investigate both theoretically and numerically the singularity formation and long time existence of three-dimensional vortex sheets. For the theoretical work, we divide it into two parts. In the first part, we study the early time singularity formation and the local form of the vortex sheet in the neighborhood of a singularity near the singularity time. We show that under a special set of coordinates, the three-dimensional vortex sheet can be viewed as a two-dimensional vortex sheet along certain space curves. As a result, the study of singularity formation of a three-dimensional vortex sheet can be related to that of the corresponding two-dimensional vortex sheet. And the singular behavior of these two problems is very similar. Moreover, by performing a transformation in the interface variables and deriving leading order asymptotic approximations for the evolution of these transformed variables, we show that the Kelvin-Helmholtz instability is a result of the coupling of two of these three variables to the leading order. This observation simplifies significantly our singularity analysis for three-dimensional vortex sheets and allows us to reveal clearly the nature of the curvature singularity in the three-dimensional vortex sheet equation. In the second part of our theoretical work, we prove the long time existence of the three-dimensional vortex sheet problem for analytic initial conditions near equilibrium. Moreover, the existence time is almost optimal if the initial perturbation over the equilibrium is sufficiently small. We have performed careful numerical study to validate our theoretical results. Well-resolved numerical study of the three-dimensional vortex sheet equation is difficult due to the complexity in evaluating the interface velocity. To alleviate this difficulty, we introduce two model equations. An important feature of these models equations is that they can be expressed in terms of convolution operators and consequently they can be computed efficiently by Fast Fourier Transform. Moreover, we show by asymptotic analysis that these model equations preserve the singularity type of the full equations. Our analysis also suggests that the model equations generate the same local form of curvature singularity near the physical singularity time as that of the full equations. Our detailed numerical computations on the two-dimensional problem show that the model equation captures all the essential singularity behavior of the full vortex sheet equation. Our calculations based on the three-dimensional model equation provide convincing evidences that a curvature singularity develops in finite time in the three-dimensional vortex sheet. And the type of the singularity is of order -1/2 in the mean curvature.
