Drag Reduction Of Turbulent Flows By Additives
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Drag Reduction Of Turbulent Flows By Additives
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Author : A. Gyr
language : en
Publisher: Springer Science & Business Media
Release Date : 2013-03-09
Drag Reduction Of Turbulent Flows By Additives written by A. Gyr and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013-03-09 with Technology & Engineering categories.
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.
Turbulent Drag Reduction By Surfactant Additives
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Author : Feng-Chen Li
language : en
Publisher: John Wiley & Sons
Release Date : 2012-01-10
Turbulent Drag Reduction By Surfactant Additives written by Feng-Chen Li and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-01-10 with Science categories.
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.
Turbulent Drag Reduction By Additives
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Author : Dilafruz Kulmatova
language : en
Publisher:
Release Date : 2013
Turbulent Drag Reduction By Additives written by Dilafruz Kulmatova and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with categories.
The addition of a minute amount of polymer or surfactant additive to a turbulent fluid flow can result in a large reduction in the frictional drag in pipes and channels. Over the past decades, numerous studies have been carried out on drag reducing additives (DRA). DRA have been successfully applied for potential benefits in various industrial processes, including oil well operations, heating and cooling water circuits, marine and biomedical systems. The use of additives to enhance flow in petroleum pipelines has received the greatest attention due to its great commercial success in reducting cost and energy consumption. Although this effect has been known for almost half a century, the detailed mechanism of drag reduction have still not been clearly identified and is still a subject of ongoing controversy. The aim of this thesis is to develop an understanding of the role of drag reducing agents and to explain the nature of drag reduction mechanism. This could have an impact on the design of efficient pumping systems, the design of drag-reducing agent that are more stable over time, and the modeling of mixing processes that could be an important consideration in designing practical systems.
Drag Reduction With The Aid Of Air Bubbles And Additives
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Author : Pouria Baghaei
language : en
Publisher:
Release Date : 2009
Drag Reduction With The Aid Of Air Bubbles And Additives written by Pouria Baghaei and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
The effect of additives on friction loss in upward turbulent flow was investigated in this experimental study. Additives such as air bubbles, frother and polymer were added to water flow to study their influence on the friction factor. In order to perform this research an experimental set-up was designed and developed. The test sections of the set-up consisted of three vertical pipes of different diameters. The set-up was equipped with three pressure transducers, a magnetic flowmeter, gas spargers and a gas rotameter. The first phase of the experimental program involved calibration of the various devices and pipelines test-sections. The single-phase pressure loss data obtained from the pipelines exhibited good agreement with the standard equations. The second phase of the experimental program dealt with the effect of air bubbles and additives (frother and polymer) on drag reduction in turbulent flows. The experimental results showed that bubbles in the range of 1 mm-3 mm increased the wall shear stress. Therefore, no drag-reduction effect was observed. On the contrary, a significant increase in friction factor was observed at low Reynolds numbers as a result of larger bubble sizes and lower turbulence intensities. The friction factor at low Reynolds numbers could be decreased by decreasing the bubble size by addition of frother to the flow system. The combination of polymer and air bubbles showed a drag reduction of up to 60%. It is also evident from the experiment results that the addition of polymer to bubbly flow system leads to fully homogeneous mixture.
Recent Developments In Turbulence Management
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Author : K.-S. Choi
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Recent Developments In Turbulence Management written by K.-S. Choi and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Technology & Engineering categories.
The European Drag Reduction Meeting has been held on 15th and 16th November 1990 in London. This was the fifth of the annual European meetings on drag reduction in engineering flows. The main objective of this meeting was to discuss up-to-date results of drag reduction research carried out in Europe. The organiser has adopted the philosophy of discussing the yesterday's results rather than the last year's results. No written material has therefore been requested for the meeting. It was only after the meeting the submission of papers was requested to the participants, from which 16 papers were selected for this proceedings volume. The meeting has attracted a record number of participants with a total of 52 researchers from seven European countries, U. K. , France, Germany, the Netherlands, Italy, Switzerland and U. S. S. R. as well as from Japan, Canada and Australia. The subjects covered in this proceedings volume include riblets, LEBUs (Large Eddy Break-Up device), surface roughness, compliant surfaces and polymer additives. Riblets seem to be one of the most extensively studied devices in the past years. Reflecting this situation in the European community, there are six papers on riblets covering their practical applications to aircraft and to a model ship, near-wall coherent structure of the boundary layer and effects of flow three-dimensionality. Possibility of heat-transfer enhancement with riblets and potential use in the laminar flow are also investigated. An analytical model is developed for the boundary-layer with a LEBU device.
Structure Of Turbulence And Drag Reduction
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Author : Albert Gyr
language : en
Publisher: Springer Science & Business Media
Release Date : 2012-12-06
Structure Of Turbulence And Drag Reduction written by Albert Gyr and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-12-06 with Science categories.
In 1976 a similar titled IUTAM Symposium (Structure of Turbulence and Drag Reduction) was held in Washington . However, the progress made during the last thirteen years as weil as the much promising current research desired a second one this year. In Washington drag reduction by additives and by direct manipulation of the walls (compliant walls and heated surfaces) were discussed. In the meantime it became evident that drag reduction also occurs when turbulence is influenced by geometrical means, e.g. by influencing the pressure distribution by the shape of the body (airfoils) or by the introduction of streamwise perturbances on a body (riblets). In the recent years turbulence research has seen increasing attention being focused on the investigation of coherent structures, mainly in Newtonian fluids. We all know that these structures are a significant feature of turbulent flows, playing an important role in the energy balance in such flows. However their place in turbulence theories as weil as the factors influencing their development are still poorly understood. Consequently, the investigation of phenomena in which the properties of coherent structures are alte red provides a promising means of improving our understanding of turbulent flows in general.
Numerical Simulation Of Turbulent Flows With Drag Reducing Polymeric Additives
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Author : Abdulmaik Abdulah Alhusseini
language : en
Publisher:
Release Date : 1989
Numerical Simulation Of Turbulent Flows With Drag Reducing Polymeric Additives written by Abdulmaik Abdulah Alhusseini and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with Fluid dynamics categories.
Analytical And Experimental Study Of Turbulent Flow Drag Reduction And Degradation With Polymer Additives
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Author : Xin Zhang
language : en
Publisher:
Release Date : 2020
Analytical And Experimental Study Of Turbulent Flow Drag Reduction And Degradation With Polymer Additives written by Xin Zhang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2020 with categories.
Flow friction reduction by polymers is widely applied in the oil and gas industry for flow enhancement or to save pumping energy. The huge benefit of this technology has attracted many researchers to investigate the phenomenon for 70 years, but its mechanism is still not clear. The objective of this thesis is to investigate flow drag reduction with polymer additives, develop predictive models for flow drag reduction and its degradation, and provide new insights into the drag reduction and degradation mechanism. The thesis starts with a semi-analytical solution for the drag reduction with polymer additives in a turbulent pipe flow. Based on the FENE-P model, the solution assumes complete laminarization and predicts the upper limitation of drag reduction in pipe flows. A new predictive model for this upper limit is developed considering viscosity ratios and the Weissenberg number - a dimensionless number related to the relaxation time of polymers. Next, a flow loop is designed and built for the experimental study of pipe flow drag reduction by polymers. Using a linear flexible polymer - polyethylene oxide (PEO) - in water, a series of turbulent flow experiments are conducted. Based on Zimm's theory and the experimental data, a correlation is developed for the drag reduction prediction from the Weissenberg number and polymer concentration in the flow. This correlation is thoroughly validated with data from the experiments and previous studies as well. To investigate the degradation of drag reduction with polymer additives, a rotational turbulent flow is first studied with a double-gap rheometer. Based on Brostow's assumption, i.e., the degradation rate of drag reduction is the same as that of the molecular weight decrease, a correlation of the degradation of drag reduction is established, along with the proposal of a new theory that the degradation is a first-order chemical reaction based on the polymer chain scission. Then, the accuracy of the Brostow's assumption is examined, and extensive experimental data indicate that it is not correct in many cases. The degradation of drag reduction with polymer additives is further analyzed from a molecular perspective. It is found that the issue with Brostow's theory is mainly because it does not consider the existence of polymer aggregates in the flow. Experimental results show that the molecular weight of the degraded polymer in the dilute solution becomes lower and the molecular weight distribution becomes narrower. An improved mechanism of drag reduction degradation considering polymer aggregate is proposed - the turbulent flow causes the chain scission of the aggregate and the degraded aggregate loses its drag-reducing ability. Finally, the mechanism of drag reduction and degradation is examined from the chemical thermodynamics and kinetics. The drag reduction phenomenon by linear flexible polymers is explained as a non-spontaneous irreversible flow-induced conformational-phase-change process that incorporates both free polymers and aggregates. The entire non-equilibrium process is due to the chain scission of polymers. This theory is shown to agree with drag reduction experimental results from a macroscopic view and polymer behaviours from microscopic views. The experimental data, predictive models, and theories developed in this thesis provide useful new insights into the design of flow drag reduction techniques and further research on this important physical phenomenon.
Drag Reduction
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Author : Pouria Baghaei
language : en
Publisher: LAP Lambert Academic Publishing
Release Date : 2012
Drag Reduction written by Pouria Baghaei and has been published by LAP Lambert Academic Publishing this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
Drag reduction is a remarkable ability to reduce the frictional resistance in the turbulent flow by adding a low concentration of certain additives, drag reducing additive agents (DRA). High costs of fluid transportation (such as pumping the liquids into the pipelines) in production processes has made drag reduction subject of lots of research in the past decades. Several studies have been carried out on reducing the friction factor in flow system using different drag reducing agents. However, there are a few investigations carried out on the effects of combining two or more DRAs. The purpose of this study is to investigate the effects of different additives on drag reduction using various methods. Effects of Polymer, Air bubbles, Aerofroth, and their combination have been investigated through the experimental study.
Experimental Investagation Of Drag Reduction Effects Of Polymer Additives On Turbulent Pipe Flow
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Author :
language : en
Publisher:
Release Date : 2005
Experimental Investagation Of Drag Reduction Effects Of Polymer Additives On Turbulent Pipe Flow written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Since the discovery of the drag reduction effects of even small amount of macromolecules in solutions in turbulent pipe flows, there have been many experimental and theoretical studies in order to understand mechanisms behind this phenomenon. Theories have been proposed based on the observations on the change in the characteristics of the turbulent flow near the pipe wall where friction of the momentum transfer between the flow and the conduit takes place. In this study drag reduction in fully developed turbulent pipe flow with four concentrations (200 to 500 wppm) of low molecular weight Sodium Carboxymethylcellulose (CMC) in aqueous solutions was investigated experimentally. Drag reduction was determined by pressure drop measurements. In order to observe the impact of the presence of CMC on the flow, Ultrasound Doppler Velocimetry (UDV) was employed to monitor the instantaneous velocity distributions. UDV is a non-invasive technique allowing one to obtain quick velocity profiles. Experimental measurements were used to calculate Fanning friction factor and radial distributions of the axial time-averaged velocity, velocity fluctuation (turbulent intensity) and eddy viscosity. The drag reduction level was determined through the Fanning friction factor versus Reynolds number data. Velocity data could be obtained as close as 3 mm to the wall by UDV. Two impacts of increasing CMC concentration on the flow field, hence pressure drop, were observed. The first effect was the decrease of the mean velocity gradient especially near the wall with increasing polymer amount which in turn gave rise to lower friction factor or pressure drop. In addition smaller eddy viscosities were obtained in the flow. The second impact of the polymer addition was on the velocity fluctuation or turbulent intensity variation along the radial distribution. An increasing trend in turbulence intensity in the turbulent core with polymer addition was observed. This was in agreement with the earlier st.
