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| Author | : John Young |
| Publisher | : |
| Total Pages | : 656 |
| Release | : 2005 |
| Genre | : Aerofoils |
| ISBN | : |
| Author | : Tejas Canchi |
| Publisher | : |
| Total Pages | : 125 |
| Release | : 2012 |
| Genre | : Insects |
| ISBN | : |
The aim of this work is to provide a better understanding of the aerodynamic performance of various planform shapes undergoing various kinematics for flapping wing flight. There have been extensive analyses and experiments of 2D airfoils undergoing flapping motion. These studies reveal various mechanisms for unsteady aerodynamic lift and thrust generation such as the importance of the control of leading edge vortices. However, 3D analysis of flapping wing flight with various planform shapes is required to study 3D flow structures and their role in determining the lift and thrust for the design of a future flapping wing micro air vehicle. Firstly, CFD analysis has been carried out on 5 rigid simple planform shapes (rectangle, reverse ellipse, ellipse, triangle and four ellipse) at a Reynolds number of 13500 to determine the effect of planform shape on the aerodynamic performance of a flapping wing undergoing hover kinematics. The kinematics is described in terms of only 2 angles, sweep and pitch. The performance is compared through the use of force histories, pressure distribution plots, flow structure images, power utilized and lift generated. It is found that the area distribution near the wing tip contributes to the difference in lift generation between the five planforms. The rectangular planform is found to have the best performance with a suitable balance of power consumed and lift generated as compared to the reverse ellipse which has the highest lift generation. Secondly, the kinematics from a honeybee and thrips are used on the same 5 planform shapes to determine the effect of kinematics on the performance of each planform. These kinematics are more realistic as the variations of all the 3 angles (sweep, pitch and elevation) are considered. It is found from the analysis that the reverse ellipse planform performs the best in terms of lift generation but the ellipse performs better overall when power economy (ratio of average vertical force generated to the average power consumed) is considered. In thrips kinematics, the reverse ellipse is again seen to perform the best in terms of the power economy. For a given planforms, there is a reduction in lift generation in thrips kinematics compared to the honeybee kinematics except in the case of the rectangle where there is an increase. These results have been explained in terms of the flow structures and associated pressure distributions generated on the wings.
| Author | : Muhammad Arif Ashraf |
| Publisher | : |
| Total Pages | : 193 |
| Release | : 2010 |
| Genre | : Aerodynamics |
| ISBN | : |
Inspired by the natural flying and swimming creatures, the application of flapping wings has attracted a great deal of attention from the scientific community in recent years. On one hand, flapping wings are expected to replace conventional rotor systems to build Micro and Nano Aerial Vehicles (MAVs and NAVs) operating at low Reynolds number while on the other hand they are also being investigated for the role of power generation in conjunction with conventional rotary wind turbines. For the development of MAVs/NAVs and understanding of unsteady aerodynamics, the current thesis fills the gaps in the current state of the flapping wing aerodynamics research. Firstly, at Reynolds number Re = 20000, the effect of large amplitude motions on the plunging airfoil propulsion is investigated with both two-dimensional (2D) and three-dimensional (3D) Navier-Stokes (NS) simulations. For a given plunging frequency, it is shown that increasing the amplitude of plunging airfoil motion causes the flow to be chaotic. From 3D simulations, it is shown that the chaotic force generation is not an artefact of 2D assumption. Secondly, the effect of airfoil shape (thickness and camber) variation on thrust and efficiency of a flapping airfoil at Reynolds number 200, 2000, 20000 and 2 x 106 is assessed with 2D NS and Unsteady Panel Method (UPM) simulations. It is found that for different Reynolds numbers, there exists an optimum thickness of symmetric airfoil section for maximum thrust and propulsive efficiency. The role of leading edge vortices is shown to be key to the observed performance variation. It is also shown that varying camber does not provide any benefit in terms of thrust or propulsive efficiency. Flapping airfoils can also be exploited to function as power generators, NS simulations are performed to study different configurations of flapping airfoils as power than the sinusoidal counterpart and the fully flow-driven simulation results show the practicality of flapping wing power generators. power generators which include single and two foils in tandem arrangement with prescribed sinusoidal and non-sinusoidal flapping motions at Re = 20000. Also, a numerical strategy is developed to model a fully flow-driven flapping foil power generator by utilising the aero-elastic response to the lift and moment acting on it. It is found that non-sinusoidal motion produces around 20% more power than the sinusoidal counterpart and the fully flow-driven simulation results show the practicality of flapping wing power generators.
| Author | : Ülgen Gülçat |
| Publisher | : Springer Nature |
| Total Pages | : 445 |
| Release | : 2021-01-04 |
| Genre | : Technology & Engineering |
| ISBN | : 3030607771 |
This book introduces the concept of unsteady aerodynamics and its underlying principles. The author provides the readers with a comprehensive review of the fundamental physics of free and forced unsteadiness, the terminology and basic equations of aerodynamics ranging from incompressible flow to hypersonics. The book also covers modern topics related to the developments made in recent years, especially in relation to wing flapping for propulsion. The book is written for graduate and senior year undergraduate students in aerodynamics and also serves as a reference for experienced researchers. Each chapter includes ample examples, questions, problems and relevant references. This 3rd edition includes a new chapter about unsteady applications related to the thrust optimization, aerodynamic stability and trim because there has been much progress in unsteady applications of the flapping wing technology. In addition, further material is presented in Appendix for evaluating the stability derivatives so that no derivation of equations is left incomplete but not overdone in the text.
| Author | : Sunetra Sarkar |
| Publisher | : LAP Lambert Academic Publishing |
| Total Pages | : 204 |
| Release | : 2010-03 |
| Genre | : |
| ISBN | : 9783838347592 |
This book analyzes the unsteady, viscous flow-field of an oscillating airfoil. This has ramifications on understanding the flapping flight of natural biological systems like fishes and invertebrates. It also helps towards a better aerodynamic design and understanding of flapping types MAVs. The flow-field simulation is performed with a grid-free Lagrangian particle based solver using vorticity particles. An examination of the unsteady aerodynamic load and the qualitative wake structures are done for airfoils undergoing pitch and plunge oscillations. The propulsive behavior is investigated at medium to high frequency ranges for different relevant parameters. These are amplitude of oscillation, mean angle of attack, and rotational axis location. Asymmetric sinusoidal motions are also examined. Dynamic stall is another important aspect of unsteady aerodynamics that airfoils and wings experience during their time dependent movement at large angles of attack. Insects use this phenomenon to increase the aerodynamic loads during their large angle flapping maneuvers. This aspect is also studied in this book.
| Author | : Tuncer Cebeci |
| Publisher | : Springer |
| Total Pages | : 0 |
| Release | : 2014-11-16 |
| Genre | : Technology & Engineering |
| ISBN | : 9783642444968 |
The standard textbooks on aerodynamics usually omit any discussion of un steady aerodynamics or, at most, consider it only in a single chapter, based on two justifications. The first is that unsteady aerodynamics should be regarded as a specialized subject required "only" in connection with understanding and an alyzing aeroelastic phenomena such as flutter and gust response, and therefore should be dealt with in related specialist books. The second reason appears to be reluctance to discuss aerodynamics with the inclusion of the time-dependent terms in the conservation equations and the boundary conditions for fear that added complications may discourage the reader. We take the opposite view in this book and argue that a full understanding of the physics of lift generation is possible only by considering the unsteady aerody namics of the starting vortex generation process. Furthermore, certain "steady" flows are inherently unsteady in the presence of flow separation, as for example the unsteady flow caused by the Karman vortex shedding downstream of a cylin der and "static" airfoil stall which is an inherently unsteady flow phenomenon. Therefore, it stands to reason that a unified treatment of aerodynamics that yields steady-state aerodynamics as a special case offers advantages. This rea soning is strengthened by the developments in computational fluid dynamics over the past forty years, which showed that accurate steady-state solutions can be obtained efficiently by solving the unsteady flow equations.
| Author | : Timothy Craig Lund |
| Publisher | : |
| Total Pages | : 80 |
| Release | : 2000-03-01 |
| Genre | : |
| ISBN | : 9781423537472 |
Flapping-wing propulsion is studied experimentally and numerically. The objective of the research is to provide further insight into the aerodynamics of flapping-wing air vehicles. Experimental work is conducted in the NPS 1.5 m x 1.5 m (5 ft x 5 ft) in-draft wind tunnel. A previously constructed long-span flapping-wing model suspended by cables is used to approximate the two-dimensional nature of the numerical simulation. For this experiment, the model is configured with two wings executing plunge-only motion. Thrust is indirectly determined by using a laser rangefinder to measure streamwise displacement of the model. Results are compared with previous experimental tests. A numerical analysis is conducted using USPOT, a locally developed unsteady panel code that models two independently moving airfoils with three degrees of freedom and non-linear deforming wakes. Thrust and efficiencies are computed for harmonically oscillating airfoils. Direct comparison is made between experimental and numerical thrust measurements.
| Author | : J. A. Burns |
| Publisher | : |
| Total Pages | : 88 |
| Release | : 1982 |
| Genre | : Aerofoils |
| ISBN | : |
This report is concerned with the development of a general mathematical model for the motion of a two-dimensional airfoil in unsteady aerodynamics and with the study of numerical schemes for estimating parameters in this model. The equations of motion are a set of coupled ordinary and functional differential equations. Approximating Wagner functions are used to construct state space models that retain the hereditary nature of unsteady fluid flow. The results of some simple numerical experiments are presented including a preliminary analysis of wind-tunnel data. (Author).
| Author | : Wei Shyy |
| Publisher | : Cambridge University Press |
| Total Pages | : 321 |
| Release | : 2013-08-19 |
| Genre | : Technology & Engineering |
| ISBN | : 1107067987 |
This is an ideal book for graduate students and researchers interested in the aerodynamics, structural dynamics and flight dynamics of small birds, bats and insects, as well as of micro air vehicles (MAVs), which present some of the richest problems intersecting science and engineering. The agility and spectacular flight performance of natural flyers, thanks to their flexible, deformable wing structures, as well as to outstanding wing, tail and body coordination, is particularly significant. To design and build MAVs with performance comparable to natural flyers, it is essential that natural flyers' combined flexible structural dynamics and aerodynamics are adequately understood. The primary focus of this book is to address the recent developments in flapping wing aerodynamics. This book extends the work presented in Aerodynamics of Low Reynolds Number Flyers (Shyy et al. 2008).
| Author | : |
| Publisher | : Springer |
| Total Pages | : 226 |
| Release | : 2005 |
| Genre | : Aerofoils |
| ISBN | : 9780966846188 |
This book provides an introduction to unsteady aerodynamics with emphasis on the analysis and computation of inviscid and viscous two-dimensional flows over airfoils at low speeds. It begins with a discussion of the physics of unsteady flows and an explanation of lift and thrust generation, airfoil flutter, gust response and dynamic stall. This is followed by an exposition of the four major calculation methods in currents use, namely inviscid-panel, boundary-layer, viscous-inviscid interaction and Navier-Stokes methods. Examples are provided to demonstrate the use of each method and panel and interactive boundary layer codes are included on the CD-ROM. Undergraduate and graduate students, teachers, scientists and engineers concerned with aeronautical, hydronautical and mechanical engineering problems will gain understanding of the physics of unsteady low-speed flows and an ability to analyze these flows with modern computational methods.
