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| Author | : Alan E. Blanchard |
| Publisher | : |
| Total Pages | : 268 |
| Release | : 1992 |
| Genre | : Disks, Rotating |
| ISBN | : |
| Author | : Joanna Ho |
| Publisher | : |
| Total Pages | : 150 |
| Release | : 2014 |
| Genre | : |
| ISBN | : |
| Author | : Dr. Muhammad Ehtisham Siddiqui |
| Publisher | : LAP Lambert Academic Publishing |
| Total Pages | : 120 |
| Release | : 2011-08 |
| Genre | : |
| ISBN | : 9783845429120 |
This book is based on the experimental study of the rotating-disk boundary-layer flow. In the case of the natural flow, different flow regimes are identified as a function of nondimensional distance, R, from the disk axis. Mean-velocity profiles initially follow the von Karman solution. At higher R, departures arise and increase with R, which are due to the spatial growth of boundary-layer instability modes, whose radial growth rates are found to match linear-theory predictions. The profiles in the fully turbulent region follow the turbulent log law and the velocity spectra exhibit Kolmogorov-type power laws. To study the response to forcing, a setup has been designed which allows the excitation of stationary (in the lab frame) disturbances or disturbances which rotate with a frequency independently of the disk frequency. The flow response to both types of forcing and two forcing element geometries was studied. Stationary forcing produces a wake which decays with distance from the element, in agreement with theory. Forcing due to rotating elements can generate growing wavepacket-like disturbances, which although nonlinear, follow trajectories close to linear-theory predictions.
| Author | : M.Y. Hussaini |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 626 |
| Release | : 2012-12-06 |
| Genre | : Science |
| ISBN | : 1461229561 |
This volume contains the proceedings of the Workshop on In stability, Transition and Turbulence, sponsored by the Institute for Computer Applications in Science and Engineering (ICASE) and the NASA Langley Research Center (LaRC), during July 8 to August 2, 1991. This is the second workshop in the series on the subject. The first was held in 1989, and its proceedings were published by Springer-Verlag under the title "Instability and Transition" edited by M. Y. Hussaini and R. G. Voigt. The objectives of these work shops are to i) expose the academic community to current technologically im portant issues of transition and turbulence in shear flows over the entire speed range, ii) acquaint the academic community with the unique combination of theoretical, computational and experimental capabilities at LaRC and foster interaction with these capabilities, and iii) accelerate progress in elucidating the fundamental phenomena of transition and turbulence, leading to improved transition and turbulence modeling in design methodologies. The research areas covered in these proceedings include receptiv ity and roughness, nonlinear theories of transition, numerical simu lation of spatially evolving flows, modelling of transitional and fully turbulent flows as well as some experiments on instability and tran sition. In addition a one-day mini-symposium was held to discuss 1 recent and planned experiments on turbulent flow over a backward facing step.
| Author | : Andrew John Colley |
| Publisher | : |
| Total Pages | : |
| Release | : 1997 |
| Genre | : |
| ISBN | : |
| Author | : Muhammad Ehtisham Siddiqui |
| Publisher | : |
| Total Pages | : 110 |
| Release | : 2011 |
| Genre | : |
| ISBN | : |
This dissertation concerns experimental work on the instability and transition of the rotating-disk boundary-layer flow. In the case of the natural flow (i.e. without forcing), measurements of mean-flow profiles, frequency spectra and phase-locked averages of the velocity time series allow us to distinguish different flow regimes as a function of nondimensional distance, R, from the disk axis. As R increases, the mean-velocity profiles initially follow the von Kármán solution. At higher R, departures arise and increase with R. These departures are due to the spatial growth of boundary-layer instability modes (cross-flow vortices), whose radial growth rates are found to match linear-theory predictions. The flow becomes transitional at R ≈ 530 and fully turbulent by R ≈ 600. The profiles in the fully turbulent region follow the log law of turbulent boundary layers and the velocity spectra exhibit Kolmogorov-type power laws. To study the response to forcing, an experimental apparatus has been designed which allows the excitation of stationary (in thelaboratory frame of reference) disturbances or disturbances which rotate with a frequency which can be varied independently of the disk rotation rate. The flow response to both types of forcing and two forcing-element geometries was studied. Stationary forcing produces a wake which decays with distance from the element, in agreement with theory. Forcing due to rotating elements can generate growing wavepacket-like disturbances, which although nonlinear, follow trajectories close to linear-theory predictions.
| Author | : Alan E. Blanchard |
| Publisher | : |
| Total Pages | : 120 |
| Release | : 1996 |
| Genre | : Aerodynamics, Hypersonic |
| ISBN | : |
One of the primary reasons for developing quiet tunnels is for the investigation of high-speed boundary-layer stability and transition phenomena without the transition-promoting effects of acoustic radiation from tunnel walls. In this experiment, a flared-cone model under adiabatic- and cooled-wall conditions was placed in a calibrated, "quiet" Mach 6 flow and the stability of the boundary layer was investigated using a prototype constant-voltage anemometer. The results of this experiment were compared with linear-stability theory predictions and good agreement was found in the prediction of second-mode frequencies and growth. In addition, the same "N = 10" criterion used to predict boundary-layer transition in subsonic, transonic, and supersonic flows was found to be applicable for the hypersonic flow regime as well. Under cooled-wall conditions, a unique set of continuous spectra data was acquired that documents the linear, nonlinear, and breakdown regions associated with the transition of hypersonic flow under low-noise conditions
| Author | : Hans U. Meier |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 512 |
| Release | : 2012-12-06 |
| Genre | : Science |
| ISBN | : 3642829945 |
The present volume entitled "Perspectives in Turbulence Stud ies" is dedicated to Dr. Ing. E. h. Julius C. Rotta in honour of his 75th birthday. J. C. Rotta, born on January 1, 1912, started his outstanding career in an unusual way, namely in a drawing office (1928 - 1931). At the same time he - as a purely self taught perso- took a correspondence course in airplane construction. From 1934 to 1945 he worked in the aircraft industry on different subjects in the fields of flight mechanics, structures, air craft design, and aerodynamics. In 1945 he moved to Gottingen and worked from that time at the Aerodynamische Versuchsanstalt (AVA, now DFVLR) and the Max-Planck-Institut fur Stromungsforschung (1947-1958), interrupted only by a stay in the U. S. at the Glenn L. Martin Company (1954 - 1955) and a visiting professorship at the Laval University in Quebec, Canada (1956). Already during his activities in industry, Dr. Rotta discovered his special liking for aerodynamics. In Gottingen, he was attracted by Ludwig Prandtl's discussions about problems associated with turbulence and in particular his new contribution to fully developed turbulence, published in 1945. At that time, W. Heisenberg and C. F. v. Weizacker pub lished their results on the energy spectra of isotropic turbu lence at large wave numbers. Since that time his main research interest in reasearch has been in turbulence problems.
| Author | : H.F. Fasel |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 703 |
| Release | : 2013-03-09 |
| Genre | : Science |
| ISBN | : 3662039974 |
The origins of turbulent flow and the transition from laminar to turbulent flow are among the most important unsolved problems of fluid mechanics and aerodynamics. Besides being a fundamental question of fluid mechanics, there are any number of applications for information regarding transition location and the details of the subsequent turbulent flow. The JUT AM Symposium on Laminar-Turbulent Transition, co-hosted by Arizona State University and the University of Arizona, was held in Sedona, Arizona. Although four previous JUT AM Symposia bear the same appellation (Stuttgart 1979, Novosibirsk 1984, Toulouse 1989, and Sendai 1994) the topics that were emphasized at each were different and reflect the evolving nature of our understanding of the transition process. The major contributions of Stuttgart 1979 centered on nonlinear behavior and later stages of transition in two-dimensional boundary layers. Stability of closed systems was also included with Taylor vortices in different geometries. The topics of Novosibirsk 1984 shifted to resonant wave interactions and secondary instabilities in boundary layers. Pipe- and channel-flow transition were discussed as model problems for the boundary layer. Investigations of free shear layers were presented and a heavy dose of supersonic papers appeared for the first time. The character of Toulouse 1989 was also different in that 3-D boundary layers, numerical simulations, streamwise vortices, and foundation papers on receptivity were presented. Sendai 1994 saw a number of papers on swept wings and 3-D boundary layers. Numerical simulations attacked a broader range of problems.
| Author | : Roberto Benzi |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 615 |
| Release | : 2012-12-06 |
| Genre | : Technology & Engineering |
| ISBN | : 9401104573 |
Under the auspices of the Euromech Committee, the Fifth European Turbulence Conference was held in Siena on 5-8 July 1994. Following the previous ETC meeting in Lyon (1986), Berlin (1988), Stockholm (1990) and Delft (1992), the Fifth ETC was aimed at providing a review of the fundamental aspects of turbulence from a theoretical, numerical and experimental point of view. In the magnificent town of Siena, more than 250 scientists from all over the world, spent four days discussing new ideas on turbulence. As a research worker in the field of turbulence, I must say that the works presented at the Conference, on which this book is based, covered almost all areas in this field. I also think that this book provides a major opportunity to have a complete overview of the most recent research works. I am extremely grateful to Prof. C. Cercignani, Dr. M. Loffredo, and Prof. R. Piva who, as members of the local organizing committee, share the success of the Conference. I also want to thank Mrs. Liu' Catena, for her invaluable contribution to the work done by the local organizing committee and the European Turbulence Committee in the scientific organization of the meeting. The "Servizio Congressi" of the University of Siena provided perfect organization in Siena and wonderful hospitality. The Conference has been supported by CNR, Cira, Alenia, the Universities of Rome "Tor Vergata" and "La Sapienza".
