Turbulent Drag Reduction by Surfactant Additives

Turbulent Drag Reduction by Surfactant Additives
Author: Feng-Chen Li
Publisher: John Wiley & Sons
Total Pages: 233
Release: 2012-01-10
Genre: Science
ISBN: 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.

Numerical Simulation of High Drag Reduction in a Turbulent Channel Flow with Polymer Additives

Numerical Simulation of High Drag Reduction in a Turbulent Channel Flow with Polymer Additives
Author: Yves Dubief
Publisher:
Total Pages: 10
Release: 2003
Genre:
ISBN:

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The addition of small amounts of long chain polymer molecules to wall-bounded flows can lead to dramatic drag reduction. Although this phenomenon has been known for about fifty years, the action of the polymers and its effect on turbulent structures are still unclear. Detailed experiments have characterized two distinct regimes (Warholic et at. 1999), which are referred to as low drag reduction (LDR) and high drag reduction (HDR). The first regime exhibits similar statistical trends as Newtonian flow: the log- law region of the mean velocity profile remains parallel to that of the Newtonian flow but its lower bound moves away from the wall and the upward shift of the log-region is a function of drag reduction, DR. Although streamwise fluctuations are increased and transverse ones are reduced, the shape of the rms velocity profiles is not qualitatively modified. At higher drag reductions, of the order of 40-50%, the flow enters the HDR regime for which the slope of the log-law is dramatically augmented and the Reynolds shear stress is small (Warholic et at. 1999; Ptasinski et at. 2001). The drag reduction is eventually bounded by a maximum drag reduction (MDR) (Virk & Mickley 1970) which is a function of the Reynolds number. while several experiments report mean velocity profiles very close to the empirical profile of Virk & Mickley (1970) for MDR conditions, the observations regarding the structure of turbulence can differ significantly. For instance, Warholic et at. (1999) measured a near-zero Reynolds shear stress, whereas a recent experiment (Ptasinski et at. 2001) shows evidence of non-negligible Reynolds stress in their MDR flow. To the knowledge of the authors, only the LDR regime has been documented in numerical simulations (Sureshkumar et at. 1997; Dimitropoulos et al. 1998; Min et at. 2001; Dubief & Lele 2001; Sibilla & Baron 2002).

Direct Numerical Simulation of Turbulent Drag Reduction: Molecular Modeling Molecular Optimization and Modeling Without Consititutive Equations

Direct Numerical Simulation of Turbulent Drag Reduction: Molecular Modeling Molecular Optimization and Modeling Without Consititutive Equations
Author:
Publisher:
Total Pages: 0
Release: 2003
Genre:
ISBN:

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We present numerical simulations of turbulent drag reduction in wall-bounded flows by additives. The bulk of the work concentrates on polymer additives. A multiscale approach was used to study the fine details of polymer dynamics in turbulence and the transfer of energy between polymers and turbulence. It was shown that polymers extract energy from near-wall vortices and release energy in high-speed streaks very close to the wall. We derived a conceptual model which applies to the two, statistically distinct regimes of polymer drag reduction, namely low drag reduction (LDR) and high drag reduction (HDR). Another additive, fibres, was found to obey to a different mechanism which requires close interaction of multiple vortices.

Turbulent Drag Reduction

Turbulent Drag Reduction
Author: Haecheon Choi
Publisher:
Total Pages: 318
Release: 1992
Genre:
ISBN:

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Aerodynamic Drag Reduction Technologies

Aerodynamic Drag Reduction Technologies
Author: Peter Thiede
Publisher: Springer Science & Business Media
Total Pages: 382
Release: 2013-06-29
Genre: Technology & Engineering
ISBN: 3540453598

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------------------------------------------------------------ This volume contains the Proceedings of the CEAS/DragNet European Drag Reduction Conference held on 19-21 June 2000 in Potsdam, Germany. This conference, succeeding the European Fora on Laminar Flow Technology 1992 and 1996, was initiated by the European Drag Reduction Network (DragNet) and organised by DGLR under the auspice of CEAS. The conference addressed the recent advances in all areas of drag reduction research, development, validation and demonstration including laminar flow technology, adaptive wing concepts, turbulent and induced drag reduction, separation control and supersonic flow aspects. This volume which comprises more than 40 conference papers is of particular interest to engineers, scientists and students working in the aeronautics industry, research establishments or academia.