An Experimental Study of Passive Drag Reduction in a Turbulent Boundary Layer by a Riblet Surface PDF Download
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Author: Seong-Ryong Park
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 410
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Book Description
Author: Seong-Ryong Park
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 410
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Book Description
Author: E. Coustols
Publisher: Springer Science & Business Media
ISBN: 9400921594
Category : Technology & Engineering
Languages : en
Pages : 183
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Book Description
Proceedings of the 4th European Drag Reduction Meeting
Author:
Publisher: AIAA
ISBN: 9781600863783
Category : Boundary layer
Languages : en
Pages : 542
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Book Description
Author: Shabnam Raayai Ardakani
Publisher:
ISBN:
Category :
Languages : en
Pages : 291
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Book Description
The surfaces of many plants and animals are covered with a variety of micro-textures such as ribs or 3D tubules which can control surface-mediated properties such as skin friction. Inspired by the drag reducing ability of these natural structures, especially the ribbed features on shark denticles, passive drag reduction strategies such as micro-fabricated riblet surfaces have been developed and studied. Microgroove textures on the surface of objects such as hulls, wings or inner surface of pipes which are aligned in the stream-wise direction have been shown to reduce the wall friction by 4 − 8%. The mechanisms suggested for this form of drag reduction are viscous retardation of the flow in the grooves (both laminar and turbulent) and the displacement of vortical structures away from the wall in turbulent flows. Due to their effectiveness in altering the boundary layer structure and reducing the viscous drag force, use of riblets have been banned in various competitions such as the America’s Cup. The current thesis work is partly focused on theoretical and numerical modelling (using the open source CFD package OpenFOAM) of the evolution of viscous boundary layers in the presence of various-shaped riblets (V-grooves as well as sinusoidal wrinkled surfaces) in high Reynolds laminar flow. We explore the effect of the dimensionless height to spacing of the grooves (aspect ratio) as well as the length of the wetted surface in the streamwise direction and how these change the total drag compared with a corresponding flat wall. We show that riblets retard the viscous flow inside the grooves and reduce the shear stress inside the grooves. But for this reduction to result in overall drag reduction, the riblet wall needs to be longer than a critical length. The total drag reduction achieved is a non-monotonic function of the aspect ratio of the riblets, with aspect ratios of order unity offering the largest reduction in the total drag. To eliminate the role of entrance effects, we additionally investigate the effect of stream-wise aligned riblet structures on fully-developed Taylor-Couette flow. We perform both experimental studies as well as time-dependent numerical simulations in both the laminar Couette and the Taylor vortex regime. We again explore the effect of the size of the riblets with respect to the geometry of the Taylor-Couette cell, as well as the aspect ratio of the riblet grooves and the shape of the grooves (V-groove, Rectangular, semi-circular, etc.). For the experiments, the cylindrical textured rotors are fabricated using 3D printing techniques and the rest of the Taylor-Couette cell is custom built using CNC machining. The test cell is then aligned and mounted on a stress-controlled rheometer to measure the velocity and the torque on the rotating inner cylinder. The numerical studies are performed using the open source CFD software package OpenFOAM to compare results and understand the physical mechanisms contributing to this drag reduction phenomenon. Again we observe a non-monotonic behavior for the reduction in torque as a function of the aspect ratio of the riblets tested, similar to the trend observed in the boundary layer analysis and we discuss the effect of changing the geometry of the flow as well as the riblet spacing on the changes in the total torque. When viewed holistically the results of these two studies show that, through careful design, a net reduction in viscous drag force can be robustly realized on micro-textured surfaces in high Reynolds number laminar flows through complex changes in near-wall stream-wise velocity profiles even in the absence of turbulent effects. The understanding of these changes can be effective in guiding the design of internal flows (pipes or ducts) and external flows (such as ship hulls, micro air vehicles or unmanned underwater vehicles) that are tailored and optimized to result in low frictional drag over the entire wetted surface in both laminar and turbulent regions.
Author: Abdolrahim Hooshmand
Publisher:
ISBN:
Category : Aerodynamics
Languages : en
Pages : 418
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Book Description
Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 704
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Book Description
Author: Mohamed Gad-el-Hak
Publisher: Springer Science & Business Media
ISBN: 3540696725
Category : Science
Languages : en
Pages : 533
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Book Description
No be certain it can is not based mathematics. knowledge if upon da Vinci, (Leonardo 1452 1519) the humankind. Thinking is one greatest of Joys of Galilei, (Galileo 1564 1642) Now I think is to be the root all hydrodynamics and is at of physical science, second the to none in its mathematics. present beauty of Thomson (William (Lord Kelvin), 1824 1907) The book contains the lecture notes of of the nine instructors at present eight the short Flow Control: Fundamentals and which held course was Practices, in the week 24 28 June and Carg6se, Corsica, France, during 1996, repeated at the of Notre 9 13 1996. University Dame, Indiana, September Following the week in the course a on same was held. Corsica, 5 day workshop topic Selected from the scheduled to 1998 workshop are papers appear early special volume of the International Journal Heat Thermo of Experimental Transfer, and Fluid All Mechanics. three events were Jean Paul dynamics, organized by Bonnet of Universit6 de Andrew Pollard of Univer Poitiers, France, Queen's at and Mohamed Gad el Hak of the of sity Kingston, Canada, University Notre U.S.A.
Author: Jonathan F. Morrison
Publisher: Springer Science & Business Media
ISBN: 1402068581
Category : Technology & Engineering
Languages : en
Pages : 456
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Book Description
The Symposium brought together many of the world’s experts in fluid mechanics, microfabrication and control theory to discover the synergy that can lead to real advances and perhaps find ways in which collaborative projects may proceed. The high profile meeting was attended by keynote speakers who are leaders in their fields. A key driver was the improvement in flow efficiency to reduce drag, and thereby emissions arising from transport. About 65 papers were presented.
Author: Eduardo A. Favret
Publisher: World Scientific
ISBN: 9812837027
Category : Science
Languages : en
Pages : 413
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Book Description
This review volume explores how the current knowledge of the biological structures occuring on the surface of moth eyes, leaves, sharkskin, and the feet of reptiles can be transferred to functional technological materials.
Author: Nik Ahmad Ridhwan Nik Mohd.
Publisher: Springer Nature
ISBN: 9819968747
Category : Technology & Engineering
Languages : en
Pages : 280
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Book Description
This book consists of selected peer-reviewed papers from the 2nd International Seminar on Aeronautics and Energy (ISAE 2022) focusing on the theme to revive the aviation industry post-COVID-19 pandemic. The topics discussed in this book include aircraft design and optimization, computational fluid dynamics (CFD) simulation and experimental aerodynamics, aircraft structure and aeroelasticity, guidance control and navigation, aircraft manufacturing and health monitoring avionics and system integration of UAV/drones, SITL AND HITL application on drones, rockets and missile, industrial wind engineering, green fuel and aviation sustainability, and aviation management. This book is a valuable resource for academicians and industry players in the field of aviation and sustainability.
