Viscous Drag Reduction in Boundary Layers
Author | : |
Publisher | : AIAA |
Total Pages | : 542 |
Release | : 1990 |
Genre | : Boundary layer |
ISBN | : 9781600863783 |
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Author | : |
Publisher | : AIAA |
Total Pages | : 542 |
Release | : 1990 |
Genre | : Boundary layer |
ISBN | : 9781600863783 |
Author | : Dennis M. Bushnell |
Publisher | : |
Total Pages | : 517 |
Release | : 1990 |
Genre | : Boundary layer |
ISBN | : 9781600865978 |
Author | : Dennis M. Bushnell |
Publisher | : |
Total Pages | : |
Release | : 1990 |
Genre | : |
ISBN | : |
Author | : C. Sinclair Wells |
Publisher | : Springer |
Total Pages | : 497 |
Release | : 2013-12-20 |
Genre | : Technology & Engineering |
ISBN | : 1489955798 |
Author | : |
Publisher | : |
Total Pages | : 18 |
Release | : 1978 |
Genre | : |
ISBN | : |
Author | : |
Publisher | : |
Total Pages | : 0 |
Release | : 1998 |
Genre | : |
ISBN | : |
New concepts for turbulent boundary layer control for viscous drag reduction have been explored through numerical experiments. Direct numerical simulations of a turbulent channel flow have been conducted to develop new robust control strategies. Three different control schemes have been developed. These include applications of neural networks, a suboptimal control theory, and systems control theory. The first two approaches were developed for viscous drag reduction in turbulent boundary layers, while the third approach was developed for delay of transition to turbulence. In all cases, surface blowing and suction was used as control input. All three approaches led to simple feedback control laws, which led to substantial viscous drag reduction (neural network and suboptimal control theory) and delay of transition (systems control theory). Implication of these results as well as issues regarding practical implementation are discussed.
Author | : Egon Stanewsky |
Publisher | : Springer Science & Business Media |
Total Pages | : 461 |
Release | : 2013-11-11 |
Genre | : Technology & Engineering |
ISBN | : 3540458565 |
The survival of the Aeronautical Industries of Europe in the highly competitive World Aviation Market is strongly dependent on such factors as time-to-market of a new or derivative aircraft and on its manufacturing costs but also on the achievement of a competitive technological advantage by which an increased market share can be gained. Recognizing this, cooperative research is continuously encouraged and co-financed by the European Union in order to strengthen the scientific and technological base of the Aeronautical Industries thus providing - among others - the technological edge needed for survival. Corresponding targets of research within Area 3, Technologies for Transport Means, and here in particular Area 3A, Aeronautics Technologies, of the Industrial and Materials Technologies Program ( Brite -EuRam III, 1994 -1998) have been identified to be aircraft efficiency, cost effectiveness and environmental impact. Concerning aircraft efficiency - relevant to the present research - a reduction in aircraft drag of 10%, a reduction in aircraft fuel consumption of 30%, and a reduction in airframe, engine and system weight of 20% are envisaged. Meeting these objectives has, of course, also a strong positive impact on the environment.
Author | : Ramakrishna Balasubramanian |
Publisher | : |
Total Pages | : 126 |
Release | : 1980 |
Genre | : Navier-Stokes equations |
ISBN | : |
Author | : Viktor V. Babenko |
Publisher | : Butterworth-Heinemann |
Total Pages | : 634 |
Release | : 2012-09-29 |
Genre | : Science |
ISBN | : 0123948215 |
While other methods of drag reduction are well-known in marine R&D and ship design environments worldwide, compliant coating drag reduction remains less well-known and poorly understood. This important book presents cutting-edge techniques and findings from research sources not generally accessible by Western researchers and engineers, aiding the application and further development of this potentially important technology. Beginning with an introduction to drag reduction that places the authors’ work on elastic surfaces and combined techniques in context, the book moves on to provide a comprehensive study of drag reduction through elastic coating with both flow and material properties considered. Coverage includes: Experimental findings around coherent vortical structures (CVS) in turbulent boundary layers and methods of controlling them Static and dynamic mechanical characteristics of elastic composite coatings, as well as new techniques and devices developed for their measurement Combined methods of flow control and drag reduction, including the effect of injection of polymer solutions, elastic coatings and generated longitudinal vortical structures on hydrodynamic resistance Intended as a reference for senior engineers and researchers concerned with the drag reduction and the dynamics of turbulent boundary layer flows, Boundary Layer Flow over Elastic Surfaces provides a unique source of information on compliant surface drag reduction and the experimental techniques around it that have shown measurable and repeatable improvements over recent years. This compilation of research findings and new techniques developed for measurement will aid R&D engineers, naval architects and senior designers in their quest to achieve drag reductions that will deliver significant efficiency savings. Unique source of information on compliant surface drag reduction—an important area of technology with practical application to ships—from otherwise inaccessible research studies Updates the knowledge-base on boundary layer flow and surface friction reduction, critical topics in the global quest for increased ship efficiency and fuel economy Reveals new techniques and devices developed for measurement and provides a comprehensive study of drag reduction through elastic coating with both flow and material properties covered
Author | : Robert K. Decker |
Publisher | : |
Total Pages | : 102 |
Release | : 2002-05 |
Genre | : Diffraction patterns |
ISBN | : 9781423510048 |
In this study two important topics have been investigated. First, a new automation procedure has been developed to detect fringe patterns in oil- film interferograms. The procedure combines a windowed Fourier transform and a cross correlation technique to determine regions where fringes are likely to reside. The cross correlation of a single cycle cosine function and the original intensity produce a filtered result that isolates the information being sought. The automation procedure is able to capture approximately 75% of the fringes in an image but additional refining of the technique could increase this percentage. Second, the effect of viscous fore-body drag on base drag has been investigated on a 2-D ramp model. Measurements made during the study include oil-film interferometry and hot-wire anemometry for viscous fore-body drag, and pressure measurements on the fore-body and base for fore-body and base drag. The results of this investigation show that an increase in viscous fore-body drag has very little effect on base drag, which contrasts previous studies where increases in viscous fore-body drag tended to decrease base drag. This means that a simple jet pumping mechanism is not the sole effect responsible for base drag reduction in this type of geometry. Hot-wire measurements in the wake of the model show that the flow in the base region is devoid of a dominant shedding frequency. It may be possible that the boundary layer somehow affects the vortex shedding mechanism but further investigations would be necessary to demonstrate that this is true.