Turbulent Drag Reduction Research

Turbulent Drag Reduction Research

Author: D. M. Bushnell

Publisher:

Published: 1984

Total Pages: 13

ISBN-13:

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This paper summarizes recent NASA research in the area of turbulent drag reduction for attached flows. The most promising passive techniques utilize non-planar geometry and indicate a possible combined net performance on the order of 20 percent. Of particular interest is the suitability of these devices for retrofit of existing vehicles. Research to optimize an active system involving tangential slot injection of low momentum (LFC) air indicates that free shear layers which are initially turbulent can be favorably controlled through use of rigid plates (large eddy-breakup devices). More conventional flow control approaches -- such as narrow-band acoustic inputs -- are evidently not effective for free mixing regions imbedded in thick turbulent layers. Experiments indicate that high frequency forcing of Emmons spots in the initial transition region to create small scale motions provides localized drag reductions, but net reductions are not yet available due to the high levels of forcing energy required.


Boundary Layer Effects

Boundary Layer Effects

Author: Anthony W. Fiore

Publisher:

Published: 1978

Total Pages: 962

ISBN-13:

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In 1975 the U.S. Air Force and the Federal Republic of Germany signed a Data Exchange Agreement numbered AF-75-G-7440 entitled 'Viscous and Interacting Flow Fields.' The purpose was to exchange data in the area of boundary layer research. It includes both experimental and theoretical boundary layer research at speeds from subsonic to hypersonic Mach numbers in the presence of laminar, transitional, and turbulent boundary layers. The main effort in recent years has been on turbulent boundary layers, both attached and separated in the presence of such parameters as pressure gradients, wall temperature, surface roughness, etc. In the United States the research was conducted in various Department of Defense, NASA, aircraft corporations, and various university laboratories. In the Federal Republic of Germany it was carried out within the various DFVLR, industrial, and university research centers.


Turbulent Drag Reduction by Surfactant Additives

Turbulent Drag Reduction by Surfactant Additives

Author: Feng-Chen Li

Publisher: John Wiley & Sons

Published: 2012-01-10

Total Pages: 233

ISBN-13: 1118181115

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Turbulent drag reduction by additives has long been a hot research topic. This phenomenon is inherently associated with multifold expertise. Solutions of drag-reducing additives are usually viscoelastic fluids having complicated rheological properties. Exploring the characteristics of drag-reduced turbulent flows calls for uniquely designed experimental and numerical simulation techniques and elaborate theoretical considerations. Pertinently understanding the turbulent drag reduction mechanism necessities mastering the fundamentals of turbulence and establishing a proper relationship between turbulence and the rheological properties induced by additives. Promoting the applications of the drag reduction phenomenon requires the knowledge from different fields such as chemical engineering, mechanical engineering, municipal engineering, and so on. This book gives a thorough elucidation of the turbulence characteristics and rheological behaviors, theories, special techniques and application issues for drag-reducing flows by surfactant additives based on the state-of-the-art of scientific research results through the latest experimental studies, numerical simulations and theoretical analyses. Covers turbulent drag reduction, heat transfer reduction, complex rheology and the real-world applications of drag reduction Introduces advanced testing techniques, such as PIV, LDA, and their applications in current experiments, illustrated with multiple diagrams and equations Real-world examples of the topic’s increasingly important industrial applications enable readers to implement cost- and energy-saving measures Explains the tools before presenting the research results, to give readers coverage of the subject from both theoretical and experimental viewpoints Consolidates interdisciplinary information on turbulent drag reduction by additives Turbulent Drag Reduction by Surfactant Additives is geared for researchers, graduate students, and engineers in the fields of Fluid Mechanics, Mechanical Engineering, Turbulence, Chemical Engineering, Municipal Engineering. Researchers and practitioners involved in the fields of Flow Control, Chemistry, Computational Fluid Dynamics, Experimental Fluid Dynamics, and Rheology will also find this book to be a much-needed reference on the topic.