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J. Gordon Leishman

Bio: J. Gordon Leishman is an academic researcher from University of Maryland, College Park. The author has contributed to research in topics: Vortex & Rotor (electric). The author has an hindex of 37, co-authored 128 publications receiving 6257 citations.


Papers
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Book
05 Jun 2000
TL;DR: A history of helicopter flight can be found in this paper, where the basic helicopter aerodynamic properties are discussed and a detailed analysis of the rotor blade motion is presented, as well as a detailed discussion of the rotor wakes and tip vortices.
Abstract: Preface Acknowledgements List of main symbols List of figures List of tables 1. Introduction: a history of helicopter flight 2. Fundamentals of rotor aerodynamics 3. Blade element analysis 4. Rotating blade motion 5. Basic helicopter performance 6. Conceptual design of helicopters 7. Rotor airfoil aerodynamics 8. Unsteady aerodynamics 9. Dynamic stall 10. Rotor wakes and tip vortices Appendix Index.

2,146 citations

Proceedings ArticleDOI
01 Jan 2002
TL;DR: Leishman et al. as mentioned in this paper used complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.
Abstract: Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately, issues discussed herein include the modeling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and misunderstandings or ambiguities can also arise in how these models should be properly applied. A challenge for analysts is to use complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.Copyright © 2002 by J. G. Leishman and ASME

334 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on two key areas that need continued serious consideration for wind turbine predictive analyses: the modeling of the rotor wake and the modelling of the unsteady aerodynamics of the blade sections.
Abstract: Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately. This article emphasizes two key areas that need continued serious consideration for wind turbine predictive analyses: the modelling of the rotor wake and the modelling of the unsteady aerodynamics of the blade sections. Issues discussed herein include the modelling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the non-linear intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and ambiguities can also arise in how these models should be properly applied. A challenge for analysts of the future is to use complementary experimental measurements and modelling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application. Copyright © 2002 John Wiley & Sons, Ltd.

316 citations

Journal ArticleDOI
TL;DR: In this paper, the theoretical basis and the numerical implementation of free-vortex filament methods are reviewed for application to the prediction and analysis of helicopter rotor wakes, with a discussion of finite difference approximations to these equations and various numerical solution techniques.
Abstract: The theoretical basis and the numerical implementation of free-vortex filament methods are reviewed for application to the prediction and analysis of helicopter rotor wakes. The governing equations for the problem are described, with a discussion of finite difference approximations to these equations and various numerical solution techniques. Both relaxation and time-marching wake solution techniques are reviewed. It is emphasized how the careful consideration of stability and convergence (grid-independent behavior) are important to ensure a physically correct wake solution. The implementation of viscous diffusion and filament straining effects are also discussed. The need for boundary condition corrections to compensate for the inevitable wake truncation are described. Algorithms to accelerate the wake solution using velocity field interpolation are shown to reduce computational costs without a loss of accuracy. Several challenging examples of the application of free-vortex filament methods to helicopter rotor problems are shown, including multirotor configurations, flight near the ground, maneuvering flight conditions, and descending flight through the vortex ring state

204 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, the aerodynamic properties of wind turbine wakes are studied, focusing on the physics of power extraction by wind turbines, and the main interest is to study how the far wake decays downstream in order to estimate the effect produced in downstream turbines.

1,161 citations

Proceedings ArticleDOI
20 Aug 2007
TL;DR: In this paper, a theoretical development is presented, and validated through both thrust test stand measurements and vehicle flight tests using the Stanford Testbed of Autonomous Rotorcraft for Multi-Agent Control (STARMAC) quadrotor helicopter.
Abstract: Quadrotor helicopters are emerging as a popular platform for unmanned aerial vehicle (UAV) research, due to the simplicity of their construction and maintenance, their ability to hover, and their vertical take o and landing (VTOL) capability. Current designs have often considered only nominal operating conditions for vehicle control design. This work seeks to address issues that arise when deviating significantly from the hover flight regime. Aided by well established research for helicopter flight control, three separate aerodynamic eects are investigated as they pertain to quadrotor flight, due to vehicular velocity, angle of attack, and airframe design. They cause moments that aect attitude control, and thrust variation that aects altitude control. Where possible, a theoretical development is first presented, and is then validated through both thrust test stand measurements and vehicle flight tests using the Stanford Testbed of Autonomous Rotorcraft for Multi-Agent Control (STARMAC) quadrotor helicopter. The results enabled improved controller performance.

1,074 citations

Journal ArticleDOI
TL;DR: In this paper, the authors classify the shape morphing parameters that can be affected by planform alteration (span, sweep, and chord), out-of-plane transformation (twist, dihedral/gull, and span-wise bending), and airfoil adjustment (camber and thickness).
Abstract: Aircraft wings are a compromise that allows the aircraft to fly at a range of flight conditions, but the performance at each condition is sub-optimal. The ability of a wing surface to change its geometry during flight has interested researchers and designers over the years as this reduces the design compromises required. Morphing is the short form for metamorphose; however, there is neither an exact definition nor an agreement between the researchers about the type or the extent of the geometrical changes necessary to qualify an aircraft for the title ‘shape morphing.’ Geometrical parameters that can be affected by morphing solutions can be categorized into: planform alteration (span, sweep, and chord), out-of-plane transformation (twist, dihedral/gull, and span-wise bending), and airfoil adjustment (camber and thickness). Changing the wing shape or geometry is not new. Historically, morphing solutions always led to penalties in terms of cost, complexity, or weight, although in certain circumstances, thes...

1,068 citations

Journal ArticleDOI
TL;DR: In this article, a review of the recent progress in flapping wing aerodynamics and aeroelasticity is presented, where it is realized that a variation of the Reynolds number (wing sizing, flapping frequency, etc.) leads to a change in the leading edge vortex (LEV) and spanwise flow structures, which impacts the aerodynamic force generation.

877 citations

Proceedings ArticleDOI
10 Dec 2007
TL;DR: This paper summarizes the final results of the modeling and control parts of OS4 project, which focused on design and control of a quadrotor and introduces a simulation model which takes into account the variation of the aerodynamical coefficients due to vehicle motion.
Abstract: The research on autonomous miniature flying robots has intensified considerably thanks to the recent growth of civil and military interest in unmanned aerial vehicles (UAV). This paper summarizes the final results of the modeling and control parts of OS4 project, which focused on design and control of a quadrotor. It introduces a simulation model which takes into account the variation of the aerodynamical coefficients due to vehicle motion. The control parameters found with this model are successfully used on the helicopter without re-tuning. The last part of this paper describes the control approach (integral backstepping) and the scheme we propose for full control of quadrotors (attitude, altitude and position). Finally, the results of autonomous take-off, hover, landing and collision avoidance are presented.

771 citations