Download or read book Drag Reduction in Near wall Turbulent Flow written by Peter North Blossey and published by . This book was released on 1999 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Viscous Drag Reduction in Boundary Layers written by and published by AIAA. This book was released on 1990 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reactive Control of Turbulent Wall Bounded Flows for Skin Friction Drag Reduction written by Stroh, Alexander and published by KIT Scientific Publishing. This book was released on 2019-01-04 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work presents an attempt to improve the understanding of reactive drag reducing control of near-wall turbulence with respect to limitations present in a realistic application scenario. The reference reactive control scheme of opposition control is studied using direct numerical simulation through the consideration of various application oriented restrictions, i.e. local control application, limited spatial and temporal resolution of the scheme, sensor noise and control elements arrangement.
Download or read book Near wall Turbulent Flows written by Ronald M. C. So and published by Elsevier Publishing Company. This book was released on 1993 with total page 1072 pages. Available in PDF, EPUB and Kindle. Book excerpt: Knowledge of near-wall turbulence from experimental, theoretical and numerical sources is accumulating at an ever increasing rate. An overview of the latest important developments is reported and discussed in depth in this volume with the goal of stimulating closer dialogue between researchers in all areas of near-wall turbulence. The full text of 95 contributed papers cover a broad range of topics in near-wall turbulent flows that includes boundary layers, coherent structures, drag reduction, experimental methods, high speed flows, numerical simulations, transition and turbulent modeling. The innovativeness of the contributions demonstrates that near-wall turbulence remains a vital and dynamically evolving field with important technological consequences for the future.
Download or read book Drag Reduction of Turbulent Flows by Additives written by A. Gyr and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Turbulent Drag Reduction by Surfactant Additives written by Feng-Chen Li and published by John Wiley & Sons. This book was released on 2012-01-10 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Recent Developments in Turbulence Management written by K.-S. Choi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Further Developments in Turbulence Management written by K. Krishna Prasad and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt: The thrust of modern research on turbulence in fluids is concerned with coherent structures and modelling. Riblets have been shown to reduce drag, and the papers presented in this volume tackle the main question of the mechanism responsible for this behaviour in turbulent flow. The contributions in this volume were presented at the Sixth Drag Reduction Meeting held at Eindhoven during November 1991. This volume will be a useful reference work for engineers, physicists and applied mathematicians interested in the topic of fluid turbulence.
Download or read book Structure of Turbulence and Drag Reduction written by Albert Gyr and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 617 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Reactive Control of Turbulent Wall Bounded Flows for Skin Friction Drag Reduction written by Alexander Stroh and published by Saint Philip Street Press. This book was released on 2020-10-09 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: The work presents an attempt to improve the understanding of reactive drag reducing control of near-wall turbulence with respect to limitations present in a realistic application scenario. The reference reactive control scheme of opposition control is studied using direct numerical simulation through the consideration of various application oriented restrictions, i.e. local control application, limited spatial and temporal resolution of the scheme, sensor noise and control elements arrangement. This work was published by Saint Philip Street Press pursuant to a Creative Commons license permitting commercial use. All rights not granted by the work's license are retained by the author or authors.
Download or read book Linearised Navier Stokes Equations and Near wall Streaks in Turbulent Flow Subject to Drag Reduction by Wall Oscillations written by Olivier Blesbois and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Spanwise wall-oscillation is a promising drag reduction technique in turbulent flows. A major factor in drag reduction is the effect of the oscillations on the boundary layer coherent structures, and particularly the weakening of the near-wall streaks. This thesis studies the streaks in various wall oscillations configurations, based on a linear approach to the turbulent flow. The two main aspects are the study of the structures themselves, and an attempt to predict drag. The streak structure is studied mainly in turbulent channel flow subject to harmonic wall forcing, using an optimal perturbation technique. It is shown that the streaks have an angle to the main flow direction, which is almost constant during half an oscillation period and experiences a jump in sign and magnitude twice per period. The linear theory shows that this phenomenon is due to the existence of a structure which is dominant during half a period and has a constant angle. Other features of the linear optimal perturbations are studied, such as their comparison with conditionally averaged turbulent structures. In order to predict drag, the optimal perturbation approach is found to be unsuitable. A more appropriate technique is to use the linearised Navier-Stokes equation subject to random forcing. This was done for a turbulent channel flow subject to travelling wave wall oscillations, thus offering a wide range of comparison with direct numerical simulations, including known regions of drag reduction and drag increase. The main finding is that in the area where drag increase is observed in turbulent flow, the linear operator is unstable. In area where the operator is stable, drag reduction is always predicted. These two topics are the core of this thesis. Other aspects include the derivation and implementation of an optimal perturbation algorithm and a linear solver. Certain theoretical aspects of the optimal perturbation approach were also investigated.
Download or read book Turbulence Control by Passive Means written by E. Coustols and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the 4th European Drag Reduction Meeting
Download or read book Drag Reduction Effects in Turbulent Boundary Layers Over Wavy Walls written by Ramakrishna Balasubramanian and published by . This book was released on 1980 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Turbulence Structure and Modulation written by Alfredo Soldati and published by Springer. This book was released on 2014-05-04 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt: Controlling turbulence is an important issue for a number of technological applications. Several methods to modulate turbulence are currently being investigated. This book describes various aspects of turbulence structure and modulation, and explains and discusses the most promising techniques in detail.
Download or read book Turbulent Flow Structure Near Walls written by J. D. A. Walker and published by . This book was released on 1991 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the past decade, progress has been made in determining the nature of turbulent flow near walls. Many of these advances, which have occurred through new experimental methodologies, direct numerical simulations, and new theoretical developments, are described in this volume.
Download or read book Near wall Turbulence and Utilisation of the Nonlinear Dynamics Towards Control of Turbulent Flows written by Anubhav Kushwaha and published by . This book was released on 2017 with total page 390 pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct numerical simulations of plane Poiseuille flow are performed in an extended domain at transitional Reynolds numbers. In minimal domains, turbulence in this Reynolds number range displays substantial intermittency that is associated with chaotic movement of turbulent trajectories between lower (LB) and upper branch (UB) invariant solutions known as exact coherent states (ECS). We address the relationship between temporal dynamics in minimal channels and spatiotemporal dynamics in extended domains. Both temporal and spatial analyses of the turbulent velocity fields are performed. These analyses partition the flow characteristics into low-, intermediate- and high-drag classes. The temporal and spatial analysis methods, although completely independent of one another, yield very similar results for both low- and high-drag regions. The conditional mean profiles in regions of low-drag closely resemble those found in low-drag temporal intervals in the minimal channel. Finally, we compare turbulence and LB-ECS and show that both the local near-wall structure in the low-drag patches of the large domain and the conditional mean profiles in the near-wall region resemble those of an LB minimal domain ECS. Lower and upper branch ECS from one particular family of solutions are imprinted separately on a turbulent flow in the minimal channel at transitional Reynolds numbers. Specifically, the spatial patterns of their wall shear stress are imprinted on the channel-wall that moves in the wall-normal direction only. The motion of the wall results in a travelling wave of wall deformation in streamwise or spanwise direction. When an LB-ECS is imprinted, drag-reduction is observed for most of the cases, and a maximum drag reduction of just over 15% is achieved. The resultant flow field shows characteristics of a flow with lesser drag and the flow trajectories pass through the vicinity of the imprinted LB-ECS in the state space. When a UB is imprinted on the flow, the drag increases. In such cases, the trajectories remain in the high-drag region of the state space. These results indicate that flow can be driven toward a desired state by manipulating the near-wall dynamics using information from that state. This opens many avenues for the development of new flow control strategies.
Download or read book Numerical Studies of Laminar and Turbulent Drag Reduction written by Ramakrishna Balasubramanian and published by . This book was released on 1983 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:
