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).

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.

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.

On the Effect of Elasticity on Drag Reduction Due to Polymer Additives Using a Hybrid D.N.S. and Langevin Dynamics Approach

On the Effect of Elasticity on Drag Reduction Due to Polymer Additives Using a Hybrid D.N.S. and Langevin Dynamics Approach
Author: Arnout Boelens
Publisher:
Total Pages: 127
Release: 2012
Genre: Drag (Aerodynamics)
ISBN:

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In this work the effect of elasticity on turbulent drag reduction due to polymers is investigated using a hybrid Direct Numerical Simulation (D.N.S) and Langevin dynamics approach. Simulations are run at a friction Reynolds number of Re_ & tau = 560 for 960.000 dumbbells with Deborah numbers of De = 0, De = 1, and De = 10. The conclusions are that it is possible to simulate a drag reduced flow using hybrid D.N.S. with Langevin dynamics, that polymers, like other occurrences of drag reduction, reduce drag through streak stabilization, and that the essential property of polymers and fibers in having a drag reducing effect is their ability to exert a torqueon the solvent when they orientate in the boundary layer of the turbulent flow.

Characterisation of Turbulent Duct Flows

Characterisation of Turbulent Duct Flows
Author: Bayode Owolabi
Publisher: Springer
Total Pages: 141
Release: 2019-05-31
Genre: Science
ISBN: 303019745X

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This book presents several new findings in the field of turbulent duct flows, which are important for a range of industrial applications. It presents both high-quality experiments and cutting-edge numerical simulations, providing a level of insight and rigour rarely found in PhD theses. The scientific advancements concern the effect of the Earth’s rotation on large duct flows, the experimental confirmation of marginal turbulence in a pressure-driven square duct flow (previously only predicted in simulations), the identification of similar marginal turbulence in wall-driven flows using simulations (for the first time by any means) and, on a separate but related topic, a comprehensive experimental study on the phenomenon of drag reduction via polymer additives in turbulent duct flows. In turn, the work on drag reduction resulted in a correlation that provides a quantitative prediction of drag reduction based on a single, measurable material property of the polymer solution, regardless of the flow geometry or concentration. The first correlation of its kind, it represents an important advancement from both a scientific and practical perspective.

Modeling and Simulation in Polymers

Modeling and Simulation in Polymers
Author: Purushottam D. Gujrati
Publisher: John Wiley & Sons
Total Pages: 564
Release: 2010-03-30
Genre: Technology & Engineering
ISBN: 9783527630264

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Filling a gap in the literature and all set to become the standard in this field, this monograph begins with a look at computational viscoelastic fluid mechanics and studies of turbulent flows of dilute polymer solutions. It then goes on discuss simulations of nanocomposites, polymerization kinetics, computational approaches for polymers and modeling polyelectrolytes. Further sections deal with tire optimization, irreversible phenomena in polymers, the hydrodynamics of artificial and bacterial flagella as well as modeling and simulation in liquid crystals. The result is invaluable reading for polymer and theoretical chemists, chemists in industry, materials scientists and plastics technologists.

Drag Reduction of Turbulent Flows by Additives

Drag Reduction of Turbulent Flows by Additives
Author: A. Gyr
Publisher: Springer Science & Business Media
Total Pages: 243
Release: 2013-03-09
Genre: Technology & Engineering
ISBN: 9401712956

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Drag Reduction of Turbulent Flows by Additives is the first treatment of the subject in book form. The treatment is extremely broad, ranging from physicochemical to hydromechanical aspects. The book shows how fibres, polymer molecules or surfactants at very dilute concentrations can reduce the drag of turbulent flow, leading to energy savings. The dilute solutions are considered in terms of the physical chemistry and rheology, and the properties of turbulent flows are presented in sufficient detail to explain the various interaction mechanisms. Audience: Those active in fundamental research on turbulence and those seeking to apply the effects described. Fluid mechanical engineers, rheologists, those interested in energy saving methods, or in any other application in which the flow rate in turbulent flow should be increased.