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Book A Method for Analyzing Dynamic Stall of Helicopter Rotor Blades

Download or read book A Method for Analyzing Dynamic Stall of Helicopter Rotor Blades written by Peter Crimi and published by . This book was released on 1972 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model for each of the basic flow elements involved in the unsteady stall of a two-dimensional airfoil in incompressible flow is presented. The interaction of these elements is analyzed using a digital computer. Computations of the loading during transient and sinusoidal pitching motions are in good qualitative agreement with measured loads. The method was used to confirm that large torsional response of helicopter blades detected in flight tests can be attributed to dynamic stall.

Book The Response and Airloading of Helicopter Rotor Blades Due to Dynamic Stall

Download or read book The Response and Airloading of Helicopter Rotor Blades Due to Dynamic Stall written by Wayne Robert Johnson and published by . This book was released on 1970 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: An aerodynamic model is constructed for the application of the properties of dynamic stall of airfoils to the calculation of the airloads and blade motion of helicopter rotor blades. Dynamic stall occurs on an airfoil undergoing pitching motion at high angle of attack, and is characterized by peak section lift and moment much larger than the corresponding static stall loads. A method is developed for the solution of the equations of motion of a rotor blade by means of harmonic analysis. The effect of dynamic stall on the blade torsional motion at high advance ratio is examined, and comparison is made with the limited experimental data available. An increase in the dynamic stall angle is shown to significantly decrease the amplitude of the pitch motions. (Author).

Book Analysis of Stall Flutter of a Helicopter Rotor Blade

Download or read book Analysis of Stall Flutter of a Helicopter Rotor Blade written by Peter Crimi and published by . This book was released on 1973 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study of rotor blade aeroelastic stability was carried out, using an analytic model of a two-dimensional airfoil undergoing dynamic stall and an elastomechanical representation including flapping, flapwise bending and torsional degrees of freedom. Results for a hovering rotor demonstrated that the models used are capable of reproducing both classical and stall flutter. The minimum rotor speed for the occurrence of stall flutter in hover, was found to be determined from coupling between torsion and flapping. Instabilities analogous to both classical and stall flutter were found to occur in forward flight. However, the large stall-related torsional oscillations which commonly limit aircraft forward speed appear to be the response to rapid changes in aerodynamic moment which accompany stall and unstall, rather than the result of an aeroelastic instability. The severity of stall-related instabilities and response was found to depend to some extent on linear stability. Increasing linear stability lessens the susceptibility to stall flutter and reduced the magnitude of the torsional response to stall and unstall.

Book Dynamic Stall of Small Wind Systems

Download or read book Dynamic Stall of Small Wind Systems written by Richard B. Noll and published by . This book was released on 1983 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Special Opportunities in Helicopter Aerodynamics

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).

Book The Rotating Beam Problem in Helicopter Dynamics

Download or read book The Rotating Beam Problem in Helicopter Dynamics written by Ranjan Ganguli and published by Springer. This book was released on 2017-10-14 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book addresses computational methods for solving the problem of vibration, response, loads and stability of a helicopter rotor blade modeled as a rotating beam with flap or out-of-plane bending. The focus is on explaining the implementation of the finite element method in the space and time domain for the free vibration, aeroelastic response and stability problems. The use of Floquet analysis for the aeroelastic stability analysis of rotor blades is also shown. The contents of the book will be useful to researchers in aerodynamics and applied mechanics, and will also serve well professionals working in the aerospace industry.

Book Comprehensive Helicopter Analysis A State of the Art Review

Download or read book Comprehensive Helicopter Analysis A State of the Art Review written by and published by . This book was released on 1978 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Dynamic Stall

Download or read book Dynamic Stall written by Peter Crimi and published by . This book was released on 1973 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Problems associated with unsteady stall are summarized and past experimental and theoretical studies, relating primarily to dynamic stall of helicopter rotor blades, are reviewed. The problems attendant to analytic treatment of dynamic stall, including identification of relevant flow elements and definition of unsteady separation, are then discussed, and the basis for a theory which accounts for viscous effects and viscous-inviscid interactions analytically is presented. Results of computations are compared with measured loading on an airfoil undergoing sinusoidal pitching motion. The amounts of lift overshoot and their variation with frequency are in good agreement. Analyses of wake-induced stall and stall flutter of a helicopter rotor blade are then presented. The results indicate that the large stall-related torsional oscillations which commonly limit helicopter forward speed are the response to rapid changes in aerodynamic moment which accompany stall and unstall, rather than the consequence of an aeroelastic instability. (Author).

Book Trailing Edge Flap Control of Dynamic Stall on Helicopter Rotor Blades

Download or read book Trailing Edge Flap Control of Dynamic Stall on Helicopter Rotor Blades written by Gregory Lloyd Davis and published by . This book was released on 2006 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book A Stall Flutter of Helicopter Rotor Blades a Special Case of the Dynamic Stall Phenomenon

Download or read book A Stall Flutter of Helicopter Rotor Blades a Special Case of the Dynamic Stall Phenomenon written by Norman D. Ham and published by . This book was released on 1967 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: Several conclusions were drawn with respect to stall flutter and airload prediction of high speed and/or highly loaded helicopter rotor blades. The stall of an airfoil section during rapid transient high angle of attack changes is delayed well above the static stall angle and results in a large transient negative pressure disturbance leading to large transient lift and nose down pitching moment. The magnitude of the pitching moment is such as to generate substantial nose down pitching displacements of the blade. These pitching displacements can substantially alter the angle of attack distribution of the rotor blade. The dynamic stall phenomenon of a helicopter rotor blade can be separated into three major phases: (1) A delay in the loss of blade leading edge suction to an angle of attack far above the static stall angle, with associated airloads of the type described by classical unsteady airfoil theory. (2) A subsequent loss of leading edge suction accompanied by the formation of large negative pressure disturbance (due to the shedding of vorticity from the vicinity of the blade leading edge) which moves aft over the upper surface of the blade. Associated with this phase are high transient lift, drag, and nose-down pitching moment associated with the greatly altered pressure distribution on the airfoil. (3) Complete upper surface separation of the classic static type, characterized by low lift, high drag, and moderate nose-down pitching moment. (Author).

Book Principles of Helicopter Aerodynamics with CD Extra

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.

Book A Method for Analyzing the Aeroelastic Stability of a Helicopter Rotor in Forward Flight

Download or read book A Method for Analyzing the Aeroelastic Stability of a Helicopter Rotor in Forward Flight written by Peter Crimi and published by . This book was released on 1969 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Aerodynamic stability of helicopter rotor in forward flight.