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Author : Ihab G. Adam
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
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:
Author : Jeffrey S. Marshall
Publisher :
ISBN 13 :
Total Pages : 50 pages
Book Rating : 4.3/5 (121 download)
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.
Author :
Publisher :
ISBN 13 :
Total Pages : 108 pages
Book Rating : 4.:/5 (317 download)
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:
Author :
Publisher :
ISBN 13 :
Total Pages : 82 pages
Book Rating : 4.:/5 (227 download)
Download or read book Experimental Investigation of Three-Dimensional Vortex-Airfoil Interaction in A Supersonic Stream written by and published by . This book was released on 1995 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt: An experimental study of the interaction between stream-wise vortices and a two-dimensional surface was conducted in a Mach 2.5 flow. The influence of oblique shock wave intensity on the inherently three-dimensional interaction was examined for vortices of variable strength. Planar laser sheet visualizations of the flowfield generated by the interaction at several distances downstream of the wedge leading edge were performed in order to gain an understanding of vortex behavior at distances further downstream. Results indicated that the interaction of a moderate strength vortex with an oblique shock wave leads to the formation of a steady separated shock structure upstream of the oblique shock front. Planar laser sheet visualization of the flowfield revealed an expansion of the vortex core in crossing a strong oblique shock front. The vortical structure was observed to persist along the entire chord of the shock generating wedge but was seen to diffuse with distances downstream of the wedge leading edge. Measurements of the vortex center above the wedge surface indicated that immediately downstream of the normal portion of the bulged-forward shock wave the vortex center was parallel to the direction of the free stream flow. (AN).
Author : Joseph Robichaux
Publisher :
ISBN 13 :
Total Pages : 414 pages
Book Rating : 4.:/5 (248 download)
Download or read book Study of Three-dimensional Vortex Shedding in the Wake of a Square Cylinder written by Joseph Robichaux and published by . This book was released on 1997 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Keith Vincent Lucas
Publisher :
ISBN 13 :
Total Pages : 306 pages
Book Rating : 4.F/5 ( download)
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:
Author : Wenhua Li
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (186 download)
Download or read book Flow/acoustics Mechanisms in Two- and Three-dimensional Wake Vortices written by Wenhua Li and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, a vortex particle method is used to simulate incompressible vortical flows, specifically aircraft wake vortices. This is particularly suitable for a wake vortex system that is slowly varying in the axial direction and has a high Reynolds number and low Mach number. The flow field, in the form of vorticity, is employed as the source in the far-field acoustic calculation using a vortex sound formula that enables computation of acoustic signals radiated from an approximated incompressible flow field. In a two-dimensional vortex system, the stretching effect in the axial direction is neglected. The purpose of this study is to focus on vortex core behaviors. A numerical simulation is performed in a more realistic wake consisting of a counter-rotating vortex pair with inviscid ground effects and shear flows. A Kirchhoff spinning-core vortex model is thus used as a starting point. In a vortex system with multiple vortices, such as a complicated aircraft vortex wake vortices, the sound emission frequency of the unsteady vortex core is subjected to change because of interactions between multiple vortices. The behaviors of the influence, indicated by the ratio between the core size and the distance of the vortices, are investigated as well as the underlining vortex core dynamic mechanisms. Cases of co-rotating vortices and a multiple-vortex system composed of two counter-rotating vortex pairs are studied for applications to aircraft wake vortex sound. In three-dimensional vortices, sinusoidal instabilities, which occur in the axial direction at various length scales, result in significant flow structure changes in these vortices, and thus influence their radiated acoustic signals. Cases of vortex rings and a pair of counter-rotating vortices are studied when they are undergoing both long-wave and short-wave instabilities. Both inviscid and viscous interactions are considered and the effects of turbulence are simulated using sub-grid-scale models. A higher peak frequency than the Kirchhoff frequency appears due to the straining field caused by mutual perturbation, under both long-wave and short-wave instabilities. Vortices with the initial core vorticity of the Gaussian distribution and the elliptic distribution are also studied.
Author : J. Wu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (681 download)
Download or read book Three-dimensional Vortex Structures in Bluff-body Wakes written by J. Wu and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The primary objective of this study was the characterization of the three-dimensional longitudinal vortices found in the wake of a circular cylinder. Using Particle Image Velocimetry (PIV) full instantaneous velocity fields were obtained in the transverse plane containing the cylinder. Footprints of the longitudinal vortices were identified, showing up as counter-rotating pairs. It appears that these vortices are embedded between, and locked to, the Karman vortices. From measured peak vorticity fields, it is clear that the longitudinal vortices are being stretched by the Karman vortices.
Author : C. R. Smith
Publisher :
ISBN 13 :
Total Pages : 99 pages
Book Rating : 4.:/5 (227 download)
Download or read book Three-Dimensional Vortex Interactions in Turbulent Boundary Layers written by C. R. Smith and published by . This book was released on 1985 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: A combined analytical experimental program, which has as its continuing objective the detailed investigation of the three dimensional vortex interactions which take place in turbulent boundary layers, is described and the accomplishments detailed. The analytical and numerical studies have examined both the development and characteristics of loop and hairpin vortices in both uniform and shear flows; particular attention has been paid to the strong three dimensional, inviscid viscous interaction of these types of vortical flow structures with wall region fluid. The experimental studies have focussed on the creation & detailed examination of three dimensional hairpin vortices, developing flow visualization patterns for cross-comparison with both the analytical studies and fully turbulent boundary layer flows. A technique for developing quantitative data by image processing of the visualization patterns is also described. Keywords: Turbulent boundary layer; Coherent structure; Flow visualization; Numerical modelling; Vortex wall interactions; Computer aided analysis; Loop vortices; Hairpin vortices.
Author : Alexandre Corjon
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Three-dimensional Instability of Wake Vortices Near the Ground written by Alexandre Corjon and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Fred H. Proctor
Publisher :
ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (613 download)
Download or read book Numerical Study of Wake Vortex Interaction with the Ground Using the Terminal Area Simulation System written by Fred H. Proctor and published by . This book was released on 1999 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Martin H. Steiger
Publisher :
ISBN 13 :
Total Pages : 20 pages
Book Rating : 4.3/5 (126 download)
Download or read book On Three-dimensional Swirling Wakes written by Martin H. Steiger and published by . This book was released on 1962 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The velocity fields of three-dimensional viscous wakes with small swirl and streamwise pressure gradients are examined with the use of the boundary layer approximations, Ossen's linearization of the convective terms, and the assumption of constant fluid properties. Transform methods yield mathematically exact solutions with general types of initial conditions. The theory, while applicable to many practical problems (such as describing the phenomena in a tip vortex), is not applied here an its application is left for future investigation.
Author : Fred H. Proctor
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (11 download)
Download or read book Numerical Study of Wake Vortex Interaction with the Ground Using the Terminal Area Simulator System written by Fred H. Proctor and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
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ISBN 13 :
Total Pages : 538 pages
Book Rating : 4.:/5 (319 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Author :
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ISBN 13 :
Total Pages : 538 pages
Book Rating : 4.3/5 (91 download)
Download or read book Aeronautical Engineering written by and published by . This book was released on 1991 with total page 538 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Valdis Kibens
Publisher :
ISBN 13 :
Total Pages : 35 pages
Book Rating : 4.:/5 (227 download)
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.
Author : National Aeronautics and Space Adm Nasa
Publisher : Independently Published
ISBN 13 : 9781794256132
Total Pages : 32 pages
Book Rating : 4.2/5 (561 download)
Download or read book Documentation for Three Wake Vortex Model Data Sets from Simulation of Flight 587 Wake Vortex Encounter Accident Case written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019-01-18 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document contains a general description for data sets of a wake vortex system in a turbulent environment. The turbulence and thermal stratification of the environment are representative of the conditions on November 12, 2001 near John F. Kennedy International Airport. The simulation assumes no ambient winds. The full three dimensional simulation of the wake vortex system from a Boeing 747 predicts vortex circulation levels at 80% of their initial value at the time of the proposed vortex encounter. The linked vortex oval orientation showed no twisting, and the oval elevations at the widest point were about 20 meters higher than where the vortex pair joined. Fred Proctor of NASA's Langley Research Center presented the results from this work at the NTSB public hearing that started 29 October 2002. This document contains a description of each data set including: variables, coordinate system, data format, and sample plots. Also included are instructions on how to read the data. Switzer, George F. Langley Research Center RTI/8438/006-02F
