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Author : Scott Thomas Shaw
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (594 download)
Download or read book Numerical Study of the Unsteady Aerodynamics of Helicopter Rotor Aerofoils written by Scott Thomas Shaw and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Study of the Unsteady Aerodynamics of Helicopter Rotor Aerofoils written by and published by . This book was released on 1903 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A two-dimensional model of the aerodynamics of rotor blades in forward flight is proposed in which the motion of the blade is represented by periodical variations of the freestrearn velocity and incidence. A novel implicit methodology for the solution of the compressible Reynolds averaged Navier-Stokes equations and a twoequation model of turbulence is developed. The spatial discretisation is based upon Osher's approximate Riernann solver, while time integration is performed using a Newton-Krylov method. The method is employed to calculate the steady transonic aerodynamics of two supercritical aerofoils and the unsteady aerodynamics of pitching aerofoils. Comparison with experiment and independent calculations for these test cases is satisfactory. Further calculations are performed for the self-excited periodic flow around a biconvex aerofoil. Comparison of quasi-steady and unsteady calculations suggests that the flow instability responsible for the self-excited flow is due to the presence of a shock induced separation bubble in the corresponding steady flow. Finally the method is used to predict the aerodynamics of aerofoils performing inplane and combined inplane-pitching motions. Results show that quasi-steady aerodynamic models are unsuitable at conditions representative of high-speed forward flight. For shock free flows, the unsteady effects of freestrearn oscillations can be represented by a simple phase lag. For transonic flows the influence of unsteadiness on shock wave dynamics is shown to be complex. Calculations for indicial motion show that the unsteady behaviour of the flow is related to the finite time taken by disturbance waves to travel to the shock wave from the leading and trailing edges of the aerofoil.
Author : Gordon J. Leishman
Publisher : Cambridge University Press
ISBN 13 : 9780521858601
Total Pages : 860 pages
Book Rating : 4.8/5 (586 download)
Download or read book Principles of Helicopter Aerodynamics with CD Extra written by Gordon J. Leishman and published by Cambridge University Press. This book was released on 2006-04-24 with total page 860 pages. Available in PDF, EPUB and Kindle. Book excerpt: Written by an internationally recognized teacher and researcher, this book provides a thorough, modern treatment of the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft such as tilt rotors and autogiros. The text begins with a unique technical history of helicopter flight, and then covers basic methods of rotor aerodynamic analysis, and related issues associated with the performance of the helicopter and its aerodynamic design. It goes on to cover more advanced topics in helicopter aerodynamics, including airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes, and rotor-airframe aerodynamic interactions, with final chapters on autogiros and advanced methods of helicopter aerodynamic analysis. Extensively illustrated throughout, each chapter includes a set of homework problems. Advanced undergraduate and graduate students, practising engineers, and researchers will welcome this thoroughly revised and updated text on rotating-wing aerodynamics.
Author : W. J. McCroskey
Publisher :
ISBN 13 :
Total Pages : 38 pages
Book Rating : 4.:/5 (317 download)
Download or read book Special Opportunities in Helicopter Aerodynamics written by W. J. McCroskey and published by . This book was released on 1983 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamic research relating to modern helicopters includes the study of three-dimensional, unsteady, nonlinear flow fields. A selective review is made of some of the phenomenon that hamper the development of satisfactory engineering prediction techniques, but which provides a rich source of research opportunities: flow separations, compressibility effects, complex vortical wakes, and aerodynamic interference between components. Several examples of work in progress are given, including dynamic stall alleviation, the development of computational methods for transonic flow, rotor-wake predictions, and blade-vortex interactions. (Author).
Author : Donald L. Kunz
Publisher :
ISBN 13 :
Total Pages : 62 pages
Book Rating : 4.:/5 (317 download)
Download or read book Effects of Unsteady Aerodynamics on Rotor Aeroelastic Stability written by Donald L. Kunz and published by . This book was released on 1977 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Billy Murel Pickelsimer
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (227 download)
Download or read book Data Reduction for the Unsteady Aerodynamics on a Circulation Control Airfoil written by Billy Murel Pickelsimer and published by . This book was released on 1977 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Calculating the lift, drag, and pitching moment coefficients for an airfoil from the static pressure distribution obtained from wind tunnel tests is routine task when steady flow is considered, but it is much more complicated when the airfoil is operating in an unsteady flow field, similar to that experienced by a helicopter rotor blade, produced by an oscillating wind tunnel. A data reduction routine capable of condensing the large numbers of data associated with the unsteady investigation, as well as a numerical integration algorithm for the unsteady aerodynamic coefficients, were developed; however, no unsteady data were collected due to hardware failures. The ability of the program was demonstrated on previously obtained steady and quasi-steady data and sample results were presented. (Author).
Author : Jaan Liiva
Publisher :
ISBN 13 :
Total Pages : 11 pages
Book Rating : 4.:/5 (464 download)
Download or read book Unsteady Aerodynamic and Stall Effects on Helicopter Rotor Blade Airfoil Sections written by Jaan Liiva and published by . This book was released on 1968 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : E. D. Bellinger
Publisher :
ISBN 13 :
Total Pages : 124 pages
Book Rating : 4.:/5 (317 download)
Download or read book Analytical Investigation of the Effects of Blade Flexibility, Unsteady Aerodynamics, and Variable Inflow on Helicopter Rotor Stall Characteristics written by E. D. Bellinger and published by . This book was released on 1971 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 62 pages
Book Rating : 4.:/5 (317 download)
Download or read book Airfoil Dynamic Stall and Rotorcraft Maneuverability written by and published by . This book was released on 2000 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt: The loading of an airfoil during dynamic stall is examined in terms of the augmented lift and the associated penalties in pitching moment and drag. It is shown that once stall occurs and a leading-edge vortex is shed from the airfoil there is a unique relationship between the augmented lift, the negative pitching moment, and the increase in drag. This relationship, referred to here as the dynamic stall function, shows limited sensitivity to effects such as the airfoil section profile and Mach number, and appears to be independent of such parameters as Reynolds number, reduced frequency, and blade sweep. For single-element airfoils there is little that can be done to improve rotorcraft maneuverability except to provide good static clmax characteristics and the chord or blade number that is required to provide the necessary rotor thrust. However, multi-element airfoils or airfoils with variable geometry features can provide augmented lift in some cases that exceeds that available from a single-element airfoil. The dynamic stall function is shown to be a useful tool for the evaluation of both measured and calculated dynamic stall characteristics of singleelement, multi-element, and variable geometry airfoils.
Author : Robert Clark
Publisher : Springer Science & Business Media
ISBN 13 : 1402021062
Total Pages : 770 pages
Book Rating : 4.4/5 (2 download)
Download or read book A Modern Course in Aeroelasticity written by Robert Clark and published by Springer Science & Business Media. This book was released on 2006-01-24 with total page 770 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this new edition, the fundamental material on classical linear aeroelasticity has been revised. Also new material has been added describing recent results on the research frontiers dealing with nonlinear aeroelasticity as well as major advances in the modelling of unsteady aerodynamic flows using the methods of computational fluid dynamics and reduced order modeling techniques. New chapters on aeroelasticity in turbomachinery and aeroelasticity and the latter chapters for a more advanced course, a graduate seminar or as a reference source for an entrée to the research literature.
Author : Bernardo Oliveira Vieira
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (1 download)
Download or read book Consideration of Unsteady Aerodynamics and Boundary-Layer Transition in Rotorcraft Airfoil Design written by Bernardo Oliveira Vieira and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Traditional rotorcraft airfoil design is based on steady-state aerodynamics, despite the many sources of unsteady-flow in forward flight. At high-thrust and high-speed conditions, the rotor may be susceptible to dynamic stall; consequently, large margins are necessary to prevent fatigue loads on the blades and pitch links, limiting operation under high altitudes, payload, and temperatures, as well as during maneuvers.This work revises typical design requirements and proposes new ways to qualify airfoils in dynamic stall. A number of design studies are conducted to better understand the relation between airfoil shape and dynamic stall behavior. The design manipulations are handled by an inverse-design, conformal mapping method, and unsteady Reynolds-averaged Navier-Stokes equations are used to predict the unsteady aerodynamic performance. In unsteady flow, the occurrence of aerodynamic lags in the development of pressures, boundary-layer separation, and viscous-inviscid interactions suggest more strict requirements than in steady flow. In order to postpone the onset of dynamic stall, the design needs to handle competing leading- and trailing-edge separation mechanisms, which are heavily influenced by shock waves and laminar-turbulent transition effects. It is found that a particular tailoring of the trailing-edge separation development can provide adequate dynamic stall characteristics and minimize penalties in drag and nose-down pitching moments. At the same time, a proper design of the nose shape is required to avoid strong shock waves and prevent premature stall. A proof-of-concept airfoil is developed to improve dynamic stall behavior, while meeting other stringent requirements. Performance calculations using information obtained from comprehensive analysis (RCAS) based on a UH-60A helicopter suggest that an expansion of the operational envelope is possible, while also reducing hover drag, maintaining low pitching moments, and providing reasonable margins to drag rise at the maximum speed of the UH-60A helicopter.Finally, pitching wing calculations are conducted to demonstrate the proposed concepts in three-dimensional flow. The new wing experiences a more favorable dynamic stall inception and considerable decreases in the integrated peak pitching moments compared to traditional designs.
Author : W. P. Jones
Publisher :
ISBN 13 :
Total Pages : 51 pages
Book Rating : 4.:/5 (353 download)
Download or read book Unsteady Aerodynamics of Helicopter Rotors written by W. P. Jones and published by . This book was released on 1972 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: ;Contents: Unsteady aerodynamics of helicopter rotors; Dynamic stall of airfoils and helicopter rotors; Computation of unsteady aerodynamic forces on helicopter rotor blades.
Author : J. Gordon Leishman
Publisher : Cambridge University Press
ISBN 13 : 9780521660600
Total Pages : 496 pages
Book Rating : 4.6/5 (66 download)
Download or read book Principles of Helicopter Aerodynamics written by J. Gordon Leishman and published by Cambridge University Press. This book was released on 2000-06-05 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: An internationally recognized expert explains the aerodynamic principles of helicopters and other rotating-wing vertical lift aircraft. Besides the history of helicopter flight, basic methods of analysis, and performance and design issues, Leishman covers airfoil flows, unsteady aerodynamics, dynamic stall, and rotor wakes. Each chapter includes homework problems.
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781722673284
Total Pages : 54 pages
Book Rating : 4.6/5 (732 download)
Download or read book Numerical Simulation and Comparison of Symmetrical/Supercritical Airfoils for the Near Tip Region of a Helicopter in Forward Flight written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-10 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamic loads on a multi-bladed helicopter rotor in forward flight at transonic tip conditions are calculated. The unsteady, three-dimensional, time-accurate compressible Reynolds-averaged thin layer Navier-Stokes equations are solved in a rotating coordinate system on a body-conformed, curvilinear grid of C-H topology. Detailed boundary layer and global numerical comparisons of NACA-0012 symmetrical and CAST7-158 supercritical airfoils are made under identical forward flight conditions. The rotor wake effects are modeled by applying a correction to the geometric angle of attack of the blade. This correction is obtained by computing the local induced downwash velocity with a free wake analysis program. The calculations are performed on the Numerical Aerodynamic Simulation Cray 2 and the VPS32 (a derivative of a Cyber 205 at the Langley Research Center) for a model helicopter rotor in forward flight. Badavi, F. F. Unspecified Center...
Author :
Publisher :
ISBN 13 :
Total Pages : 704 pages
Book Rating : 4.:/5 (31 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Cameron Tropea
Publisher : Springer Science & Business Media
ISBN 13 : 3540251413
Total Pages : 1570 pages
Book Rating : 4.5/5 (42 download)
Download or read book Springer Handbook of Experimental Fluid Mechanics written by Cameron Tropea and published by Springer Science & Business Media. This book was released on 2007-10-09 with total page 1570 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accompanying DVD-ROM contains ... "all chapters of the Springer Handbook."--Page 3 of cover.
Author : Mark A. Couch
Publisher :
ISBN 13 :
Total Pages : 58 pages
Book Rating : 4.:/5 (122 download)
Download or read book A Finite Wake Theory for Two-dimensional Rotary Wing Unsteady Aerodynamics written by Mark A. Couch and published by . This book was released on 1993 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unsteady aerodynamic forces and moments of an oscillating airfoil for the fixed wing case were determined by Theodorsen along with the development of a lift deficiency function. Loewy subsequently developed an analogous lift deficiency function for the rotary wing case in which there are an infinite number of layers of shed vorticity, or wakes, below the reference airfoil. With the advent of computer panel codes that calculate the time histories of the wakes generated by oscillating airfoils, a theory is developed for the rotary wing case in which there are a finite number of layers of shed vorticity below the reference airfoil. This theory includes a lift deficiency function that is completely analogous to Loewy and Theodorsen. It has long been recognized that an airfoil oscillating in pure plunge produces a propulsive force (Katzmayr effect). Garrick used Theodorsen's work to develop equations for the propulsive force that include the lift deficiency function as a parameter. When either Loewy's lift deficiency function or the finite wake lift deficiency function is used, the effect of the propulsive force is greatly enhanced with the proper phase relationship of the wakes. The finite wake theory along with Garrick's work is used to describe the performance characteristics of Higher Harmonic Control. Specifically for the OH-6A, coupled pitch-plunge motion results in a propulsive force that significantly reduces the rotor drag force. Helicopter, Rotary wing, Unsteady aerodynamics, Wake, Propulsive force, Higher harmonic control, Hummingbird.
