Download or read book A Comparison of Plane Turbulent Wakes by Digital Image Analysis Techniques written by Dennis Frank Visentin and published by . This book was released on 1985 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Masters Theses in the Pure and Applied Sciences written by Wade H. Shafer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: Masters Theses in the Pure and Applied Sciences was first conceived, published, SIld disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna and broader dissemination. tional publishing house to assure improved service Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 30 (thesis year 1985) a total of 12,400 theses titles from 26 Canadian and 186 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work.
Download or read book Vortex wakes of Aircrafts written by A.S. Ginevsky and published by Springer Science & Business Media. This book was released on 2009-07-07 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigation of vortex wakes behind various aircraft, especially behind wide bodied and heavy cargo ones, is of both scientific and practical in terest. The vortex wakes shed from the wing’s trailing edge are long lived and attenuate only atdistances of10–12kmbehindthe wake generating aircraft. The encounter of other aircraft with the vortex wake of a heavy aircraft is open to catastrophic hazards. For example, air refueling is adangerous operationpartly due to thepossibility of the receiver aircraft’s encountering the trailing wake of the tanker aircraft. It is very important to know the behavior of vortex wakes of aircraft during theirtakeoff andlanding operations whenthe wakes canpropagate over the airport’s ground surface and be a serious hazard to other depart ing or arriving aircraft. This knowledge can help in enhancing safety of aircraft’s movements in the terminal areas of congested airports where the threat of vortex encounters limits passenger throughput. Theoreticalinvestigations of aircraft vortex wakes arebeingintensively performedinthe major aviationnations.Usedforthispurpose are various methods for mathematical modeling of turbulent flows: direct numerical simulation based on the Navier–Stokes equations, large eddy simulation using the Navier–Stokes equations in combination with subrigid scale modeling, simulation based on the Reynolds equations closed with a differential turbulence model. These approaches are widely used in works of Russian and other countries’ scientists. It should be emphasized that the experiments in wind tunnels and studies of natural vortex wakes behind heavy and light aircraft in flight experiments are equally important.
Download or read book Journal of Fluids Engineering written by and published by . This book was released on 1997 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Wake Turbulence written by National Research Council and published by National Academies Press. This book was released on 2008-04-27 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Without major changes, the current air transportation system will be unable to accommodate the expected increase in demand by 2025. One proposal to address this problem is to use the Global Positioning System to enable aircraft to fly more closely spaced. This approach, however, might be limited by the wake turbulence problem, which can be a safety hazard when smaller aircraft follow relatively larger aircraft too closely. To examine how this potential hazard might be reduced, Congress in 2005 directed NASA to request a study from the NRC to assess the federal wake turbulence R&D program. This book provides a description of the problem, an assessment of the organizational challenges to addressing wake turbulence, an analysis of the technical challenges in wake turbulence, and a proposal for a wake turbulence program plan. A series of recommendations for addressing the wake turbulence challenge are also given.
Download or read book Applied Mechanics Reviews written by and published by . This book was released on 1965 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of the Coherent Structures in Uniformly Distorted Plane Turbulent Wakes microform written by Gregory Alan Kopp and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 1995 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aircraft Wake Turbulence and Its Detection written by John Olsen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 599 pages. Available in PDF, EPUB and Kindle. Book excerpt: The combination of increasing airport congestion and the ad vent of large transports has caused increased interest in aircraft wake turbulence. A quantitative understanding of the interaction between an aircraft and the vortex wake of a preceding aircraft is necessary for planning future high density air traffic patterns and control systems. The nature of the interaction depends on both the characteristics of the following aircraft and the characteristics of the wake. Some of the questions to be answered are: What deter mines the full characteristics of the vortex wake? What properties of the following aircraft are important? What is the role of pilot response? How are the wake characteristics related to the genera ting aircraft parameters? How does the wake disintegrate and where? Many of these questions were addressed at this first Aircraft Wake Turbulence Symposium sponsored by the Air Force Office of Sci entific Research and The Boeing Company. Workers engaged in aero dynamic research, airport operations, and instrument development came from several count ries to present their results and exchange information. The new results from the meeting provide a current picture of the state of the knowledge on vortex wakes and their interactions with other aircraft. Phenomena previously regarded as mere curiosities have emerged as important tools for understanding or controlling vortex wakes. The new types of instability occurring within the wake may one day be used for promoting early dis integration of the hazardous twin vortex structure.
Download or read book On a General Similarity Analysis for Turbulent Jet and Wake Flows written by Eduard Naudascher and published by . This book was released on 1967 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of any inhomogeneous free-turbulence flow in an incompressible fluid is predicted through the use of a general self-preservation hypothesis. The analytical solutions are verified by comparison with experimental data on mean-flow and turbulence characteristics of plane and axisymmetric jets in coaxial parallel flow with and without confinement, of an axisymmetric jet in a cross flow, and of the wake behind a self-propelled body. Emphasis is placed on the distinct turbulence structure of the various flows as revealed by the different axial variations of a shear parameter relating turbulence shear to mean velocity. The satisfactory predictions obtained by the new approach make it appear to have a more general application (e.g., to plumes and wall jets) than the examples chosen might imply. (Author).
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1996 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 488 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.
Download or read book Study of Coherent Structures Within Plane Turbulent Wakes Using a Pattern recognition Technique microform written by Leon M.* Zucherman and published by National Library of Canada. This book was released on 1988 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Controllability and Evolution of Coherent Structures in Turbulent Wakes written by John L. Way and published by . This book was released on 1980 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt: The main objectives were to answer some of the questions of evolution of large scale structure in turbulent wakes and to develop new techniques of experimentation and data reduction to identify and document the organized structures in turbulent flows. The techniques of thermal tagging, polychromatic signal decomposition, local and convective flow visualization, digital image processing and pattern recognition, two-dimensional spectral decomposition of velocity fields, as well as spatial reconstruction are applied to the bluff body wake problem. The results of these experiments have clarified the picture of wake evolution over a wide range of Reynolds numbers, from laminar to turbulent. These techniques demonstrate that an approach as elaborate as the orthogonal decomposition scheme in not necessary to objectively bring out the important large scale mechanisms. The study also clearly refutes the pairing mechanism active in shear layers as that responsible for the growth of the large scale.
Download or read book Pattern Recognition Analysis of Coherent Structures in Distorted and Undistorted Plane Turbulent Wakes written by Zheng Huang and published by . This book was released on 1994 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aircraft Wake Turbulence and Its Detection written by J.H. Olsen and published by . This book was released on 1971 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Direct Simulation of a Self Similar Plane Wake written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-08-16 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct simulations of two time-developing turbulent wakes have been performed. Initial conditions for the simulations were obtained from two realizations of a direct simulation of a turbulent boundary layer at momentum thickness Reynolds number 670. In addition, extra two dimensional disturbances were added in one of the cases to mimic two dimensional forcing. The unforced wake is allowed to evolve long enough to attain self similarity. The mass-flux Reynolds number (equivalent to the momentum thickness Reynolds number in spatially developing wakes) is 2000, which is high enough for a short k(exp -5/3) range to be evident in the streamwise one dimensional velocity spectrum. Several turbulence statistics have been computed by averaging in space and over the self-similar period in time. The growth rate in the unforced flow is low compared to experiments, but when this growth-rate difference is accounted for, the statistics of the unforced case are in reasonable agreement with experiments. However, the forced case is significantly different. The growth rate, turbulence Reynolds number, and turbulence intensities are as much as ten times larger in the forced case. In addition, the forced flow exhibits large-scale structures similar to those observed in transitional wakes, while the unforced flow does not. Moser, Robert D. and Rogers, Michael M. Ames Research Center NASA-TM-108815, A-94070, NAS 1.15:108815 RTOP 505-59-50...
Download or read book Simulation based Analyses of Turbulent Wakes written by Sheel Nidhan and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Turbulent wakes are pervasive in man-made and natural environments. In the ocean and the atmosphere, these wakes interact with the background ambient stratification to give rise to a myriad of interesting phenomena, e.g., multistage decay of mean and turbulence, long-lived coherent structures, and the appearance of internal gravity waves, to name a few. With the rise in supercomputing power, high-fidelity numerical simulations have become an increasingly feasible way to investigate the phenomenology of these wakes. As these simulations become commonplace in research, there is an increased focus on the use of data-driven techniques to uncover the rich dynamics from the obtained datasets. This dissertation is an examination of turbulent wakes using data-driven techniques and numerical simulations. In the first part, spectral proper orthogonal decomposition is used to investigate a turbulent disk wake database at Re = 5 x 104 and Fr = [infinity], 10, 2. We first study the evolution of the vortex shedding mode and double helix mode in the unstratified wake (Fr = [infinity]), building on and refining the previous experimental studies. Thereafter, the SPOD analysis of the stratified wakes is performed that uncovers two new results: (a) coherence originating at the body gets stronger and lives longer with progressively increasing stratification levels and (b) for Fr [greater than and approximately equal to] 2, vortex shedding is the dominant mechanism of internal gravity wave generation. In the second part of the work, large eddy simulations (LES) are used to investigate the flow past a prolate 6:1 spheroid. Firstly, high-resolution hybrid simulation is used to simulate the far wake of a 6:1 spheroid at 0-degree angle of attack and Re = 105, Fr = 2 and 10. The far wake is compared to the above-mentioned disk database. The spheroid wakes show differences in locations at which mean wake transitions take place. These differences are explained in light of energy budgets. Secondly, large eddy simulations of flow past a 6:1 spheroid at Re = 5000, Fr = [infinity], 6, 1.9, 1, and a moderate angle of attack [alpha] = 10[superscript circle] are carried out. Body forces, mean wake and vorticity dynamics, and flow spectra are analyzed in detail and presented in the dissertation.
