Experimental Investigation of Transition to Turbulence As Affected by Passing Wakes
Experimental Investigation of Transition to Turbulence As Affected by Passing Wakes

Author: National Aeronautics and Space Administration (NASA)

Publisher: Createspace Independent Publishing Platform

Published: 2018-06-27

Total Pages: 254

ISBN-13: 9781721940462

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Experimental results from a study of the effects of passing wakes upon laminar-to-turbulent transition in a low-pressure turbine passage are presented. The test section geometry is designed to simulate the effects of unsteady wakes resulting from rotor-stator interaction upon laminar-to-turbulent transition in turbine blade boundary layers and separated flow regions over suction surfaces. Single-wire, thermal anemometry techniques were used to measure time-resolved and phase-averaged, wall-normal profiles of velocity, turbulence intensity, and intermittency at multiple streamwise locations over the turbine airfoil suction surface. These data are compared to steady state, wake-free data collected in the same geometry to identify the effects of wakes upon laminar-to-turbulent transition. Results are presented for flows with a Reynolds number based on suction surface length and exit velocity of 50,000 and an approach flow turbulence intensity of 2.5 percent. From these data, the effects of passing wakes and associated increased turbulence levels and varying pressure gradients on transition and separation in the near-wall flow are presented. The results show that the wakes affect transition both by virtue of their difference in turbulence level from that of the free-stream but also by virtue of their velocity deficit relative to the freestream velocity, and the concomitant change in angle of attack and temporal pressure gradients. The results of this study seem to support the theory that bypass transition is a response of the near-wall viscous layer to pressure fluctuations imposed upon it from the free-stream flow. The data also show a significant lag between when the wake is present over the surface and when transition begins. The accompanying CD-ROM includes tabulated data, animations, higher resolution plots, and an electronic copy of this report. Kaszeta, Richard W. and Simon, Terrence W. and Ashpis, David (Technical Monitor) Glenn Research Center NCC3-652; RTOP 71

Elements of Transitional Boundary-Layer Flowlements
Elements of Transitional Boundary-Layer Flowlements

Author: Robert Edward Mayle

Publisher: Logos Verlag Berlin GmbH

Published: 2018

Total Pages: 418

ISBN-13: 3832545980

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Second Enhanced Edition Suitable for advanced-level courses or an independent study in fluid mechanics, this text by an expert in the field provides the basic aspects of laminar-to-turbulent flow transition in boundary layers. Logically organized into three major parts, the book covers pre- and post-transitional flow, transitional flow, and several advanced topics in periodically disturbed transitional flow. Some of the subjects covered within the book include high-frequency unsteady laminar flow, turbulent flow, natural transition, bypass transition, turbulent spot theory, turbulent spot kinematics and production, correlations for the onset and rate of transition, global and conditional averaging, transitional flow models, wakeinduced transition, multimode transition, and separated-flow transition. Containing some 202 figures (all drawn by the author), 28 tables, 12 appendices, a supplement on tensors, and an extensive bibliography, the 415 page book provides a wealth of data and information about the subject.

Fluid Mechanics for Engineers
Fluid Mechanics for Engineers

Author: Meinhard T. Schobeiri

Publisher: Springer Science & Business Media

Published: 2010-03-27

Total Pages: 517

ISBN-13: 3642115942

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The contents of this book covers the material required in the Fluid Mechanics Graduate Core Course (MEEN-621) and in Advanced Fluid Mechanics, a Ph. D-level elective course (MEEN-622), both of which I have been teaching at Texas A&M University for the past two decades. While there are numerous undergraduate fluid mechanics texts on the market for engineering students and instructors to choose from, there are only limited texts that comprehensively address the particular needs of graduate engineering fluid mechanics courses. To complement the lecture materials, the instructors more often recommend several texts, each of which treats special topics of fluid mechanics. This circumstance and the need to have a textbook that covers the materials needed in the above courses gave the impetus to provide the graduate engineering community with a coherent textbook that comprehensively addresses their needs for an advanced fluid mechanics text. Although this text book is primarily aimed at mechanical engineering students, it is equally suitable for aerospace engineering, civil engineering, other engineering disciplines, and especially those practicing professionals who perform CFD-simulation on a routine basis and would like to know more about the underlying physics of the commercial codes they use. Furthermore, it is suitable for self study, provided that the reader has a sufficient knowledge of calculus and differential equations. In the past, because of the lack of advanced computational capability, the subject of fluid mechanics was artificially subdivided into inviscid, viscous (laminar, turbulent), incompressible, compressible, subsonic, supersonic and hypersonic flows.

An Experimental Investigation of Artificially Induced Transition to Turbulence on a Body of Revolution
An Experimental Investigation of Artificially Induced Transition to Turbulence on a Body of Revolution

Author: William F. Shivitz

Publisher:

Published: 1975

Total Pages: 120

ISBN-13:

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Transition to turbulence in a boundary layer continues to be a topic of considerable interest to both aerodynamicists and hydrodynamicists. The present study focuses on the particular aspect of the problem pertaining to transition zone characteristics induced by a circular trip wire located upstream of the point of instability on a blunt nosed body of revolution. The actual transition to turbulence occurs in a region of adverse pressure gradient. The study was made on an eight-inch diameter body of revolution which had a blunt nose faired to a cylindrical afterbody with a modified ellipsoid contour. The velocity field was measured with hot-wire sensors and analyzed using analog techniques to determine velocity, intermittency, spatial correlation, and spectral characteristics. Transition to turbulence was found to be very sensitive to trip wire diameter and location and to the free-stream Reynolds number. Certain of the high amplitude instability waves induced by the trip mechanism were observed to be selectively amplified into transition in a manner similar to that predicted by stability theory. Secondary instabilities were observed to contribute to the transition process. Cross spectral densities were measured for the bursts moving downstream to determine if any narrowband range of frequencies were present which could contribute to far-field noise radiated from the boundary layer. A one-third octave filter was used to determine spectral velocity fluctuation concentrations of the bursts at a location within the transition region and compared to similar concentrations at a fully turbulent location. (Author).

Advanced Fluid Mechanics and Heat Transfer for Engineers and Scientists
Advanced Fluid Mechanics and Heat Transfer for Engineers and Scientists

Author: Meinhard T. Schobeiri

Publisher: Springer Nature

Published: 2022-01-17

Total Pages: 602

ISBN-13: 3030729257

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The current book, Advanced Fluid Mechanics and Heat Transfer is based on author's four decades of industrial and academic research in the area of thermofluid sciences including fluid mechanics, aero-thermodynamics, heat transfer and their applications to engineering systems. Fluid mechanics and heat transfer are inextricably intertwined and both are two integral parts of one physical discipline. No problem from fluid mechanics that requires the calculation of the temperature can be solved using the system of Navier-Stokes and continuity equations only. Conversely, no heat transfer problem can be solved using the energy equation only without using the Navier-Stokes and continuity equations. The fact that there is no book treating this physical discipline as a unified subject in a single book that considers the need of the engineering and physics community, motivated the author to write this book. It is primarily aimed at students of engineering, physics and those practicing professionals who perform aero-thermo-heat transfer design tasks in the industry and would like to deepen their knowledge in this area. The contents of this new book covers the material required in Fluid Mechanics and Heat Transfer Graduate Core Courses in the US universities. It also covers the major parts of the Ph.D-level elective courses Advanced Fluid Mechanics and Heat Transfer that the author has been teaching at Texas A&M University for the past three decades.

Journal of Thermophysics and Heat Transfer
Journal of Thermophysics and Heat Transfer

Author:

Publisher:

Published: 2004

Total Pages: 1238

ISBN-13:

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This journal is devoted to the advancement of the science and technology of thermophysics and heat transfer through the dissemination of original research papers disclosing new technical knowledge and exploratory developments and applications based on new knowledge. It publishes papers that deal with the properties and mechanisms involved in thermal energy transfer and storage in gases, liquids, and solids or combinations thereof. These studies include conductive, convective, and radiative modes alone or in combination and the effects of the environment.