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Download or read book Analysis of Rotor Wake Aerodynamics During Maneuvering Flight Using a Free-vortex Wake Methodology written by and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 52 pages
Book Rating : 4.:/5 (317 download)
Download or read book Free Wake Techniques for Rotor Aerodynamic Analysis. Volume 1: Summary of Results and Background Theory written by and published by . This book was released on 1982 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 200 pages
Book Rating : 4.:/5 (317 download)
Download or read book Analytical Model of Rotor Wake Aerodynamics in Ground Effect written by and published by . This book was released on 1983 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 76 pages
Book Rating : 4.:/5 (317 download)
Download or read book Free Wake Techniques for Rotor Aerodynamic Analysis. Volume 3: Vortex Filament Models written by and published by . This book was released on 1982 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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ISBN 13 :
Total Pages : 52 pages
Book Rating : 4.:/5 (227 download)
Download or read book New Vortex Dynamics Methods for Rotor Free Wake Analysis written by and published by . This book was released on 1993 with total page 52 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report summarizes recent work on rotorcraft aerodynamics involving novel methods for rotor free wake calculations. A new method called Analytical/Numerical Matching (ANM) was developed. ANM is a hybrid analytical and numerical method that achieves accurate results by combining a low resolution numerical solution with a high resolution analytical solution. Although originally developed for vortex dynamics, ANM has proven to be of a general nature. The application of ANM to the rotor wake problem provides accurate answers with a significant reduction in computation time. The use of ANM introduces the opportunity to develop new solution strategies, including Far-Field Linearization and Periodic Inversion. These methods afford the means to obtain accurate solutions Over the entire flight regime. Work involving applications of ANM has also led to a scheme that represents vortex filament dynamics by a hierarchy of nested problems of varying resolution joined by matching solutions. This approach, called ANM with Pyramiding (ANM/P), has reduced calculation times by more than a factor of twenty in some sample problems.
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ISBN 13 :
Total Pages : 168 pages
Book Rating : 4.:/5 (317 download)
Download or read book Free Wake Techniques for Rotor Aerodynamic Analylis. Volume 2: Vortex Sheet Models written by and published by . This book was released on 1982 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : A.S. Ginevsky
Publisher : Springer Science & Business Media
ISBN 13 : 3642017606
Total Pages : 166 pages
Book Rating : 4.6/5 (42 download)
Download or read book Vortex wakes of Aircrafts written by A.S. Ginevsky and published by Springer Science & Business Media. This book was released on 2009-07-07 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigation of vortex wakes behind various aircraft, especially behind wide bodied and heavy cargo ones, is of both scientific and practical in terest. The vortex wakes shed from the wing’s trailing edge are long lived and attenuate only atdistances of10–12kmbehindthe wake generating aircraft. The encounter of other aircraft with the vortex wake of a heavy aircraft is open to catastrophic hazards. For example, air refueling is adangerous operationpartly due to thepossibility of the receiver aircraft’s encountering the trailing wake of the tanker aircraft. It is very important to know the behavior of vortex wakes of aircraft during theirtakeoff andlanding operations whenthe wakes canpropagate over the airport’s ground surface and be a serious hazard to other depart ing or arriving aircraft. This knowledge can help in enhancing safety of aircraft’s movements in the terminal areas of congested airports where the threat of vortex encounters limits passenger throughput. Theoreticalinvestigations of aircraft vortex wakes arebeingintensively performedinthe major aviationnations.Usedforthispurpose are various methods for mathematical modeling of turbulent flows: direct numerical simulation based on the Navier–Stokes equations, large eddy simulation using the Navier–Stokes equations in combination with subrigid scale modeling, simulation based on the Reynolds equations closed with a differential turbulence model. These approaches are widely used in works of Russian and other countries’ scientists. It should be emphasized that the experiments in wind tunnels and studies of natural vortex wakes behind heavy and light aircraft in flight experiments are equally important.
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781722972912
Total Pages : 142 pages
Book Rating : 4.9/5 (729 download)
Download or read book Computation of Rotor Aerodynamic Loads in Forward Flight Using a Full-Span Free Wake Analysis written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of an advanced computational analysis of unsteady aerodynamic loads on isolated helicopter rotors in forward flight is described. The primary technical focus of the development was the implementation of a freely distorting filamentary wake model composed of curved vortex elements laid out along contours of constant vortex sheet strength in the wake. This model captures the wake generated by the full span of each rotor blade and makes possible a unified treatment of the shed and trailed vorticity in the wake. This wake model was coupled to a modal analysis of the rotor blade dynamics and a vortex lattice treatment of the aerodynamic loads to produce a comprehensive model for rotor performance and air loads in forward flight dubbed RotorCRAFT (Computation of Rotor Aerodynamics in Forward Flight). The technical background on the major components of this analysis are discussed and the correlation of predictions of performance, trim, and unsteady air loads with experimental data from several representative rotor configurations is examined. The primary conclusions of this study are that the RotorCRAFT analysis correlates well with measured loads on a variety of configurations and that application of the full span free wake model is required to capture several important features of the vibratory loading on rotor blades in forward flight. Quackenbush, Todd R. and Bliss, Donald B. and Wachspress, Daniel A. and Boschitsch, Alexander H. and Chua, Kiat Unspecified Center AERODYNAMIC LOADS; COMPUTATIONAL FLUID DYNAMICS; HELICOPTERS; HORIZONTAL FLIGHT; ROTARY WINGS; ROTOR AERODYNAMICS; ROTOR DYNAMICS; WAKES; UNSTEADY AERODYNAMICS; VIBRATORY LOADS; VORTEX SHEETS; VORTICES...
Author : Wayne Johnson
Publisher : Cambridge University Press
ISBN 13 : 1107028078
Total Pages : 949 pages
Book Rating : 4.1/5 (7 download)
Download or read book Rotorcraft Aeromechanics written by Wayne Johnson and published by Cambridge University Press. This book was released on 2013-04-29 with total page 949 pages. Available in PDF, EPUB and Kindle. Book excerpt: A rotorcraft is a class of aircraft that uses large-diameter rotating wings to accomplish efficient vertical take-off and landing. The class encompasses helicopters of numerous configurations (single main rotor and tail rotor, tandem rotors, coaxial rotors), tilting proprotor aircraft, compound helicopters, and many other innovative configuration concepts. Aeromechanics covers much of what the rotorcraft engineer needs: performance, loads, vibration, stability, flight dynamics, and noise. These topics include many of the key performance attributes and the often-encountered problems in rotorcraft designs. This comprehensive book presents, in depth, what engineers need to know about modelling rotorcraft aeromechanics. The focus is on analysis, and calculated results are presented to illustrate analysis characteristics and rotor behaviour. The first third of the book is an introduction to rotorcraft aerodynamics, blade motion, and performance. The remainder of the book covers advanced topics in rotary wing aerodynamics and dynamics.
Author : Todd R. Quackenbush
Publisher :
ISBN 13 :
Total Pages : 65 pages
Book Rating : 4.:/5 (227 download)
Download or read book Vortex Dynamics for Rotorcraft Interactional Aerodynamics written by Todd R. Quackenbush and published by . This book was released on 1988 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt: Promising results were obtained that indicate that new techniques in the analysis of vortex dynamics could be used as the foundation of a general analysis of rotor/airframe interactions. Prediction of the velocity field downstream of helicopter rotors was addressed first. Using a novel, full-span rotor wake representation constructed of curved vortex elements, accurate qualitative and quantitative predictions of wake velocity data were achieved for rotors in both low- and high-speed forward flight. The flow field predictions illustrated the radical changes that take place in the wake velocity field as speed increases and demonstrated the success of this approach in capturing these variations. New methods for analyzing close interactions between vortices and fixed surfaces were developed. The basis of this new approach is the inclusion of the special treatment of the vortex velocity field for close interactions with paneled surfaces which obviates the need for high local panel density. Model problems were solved featuring vortices in close proximity to flat surfaces and cylinders that amply illustrate the accuracy and efficiency of the new method. (EDC).
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781720712114
Total Pages : 30 pages
Book Rating : 4.7/5 (121 download)
Download or read book Rotor Wake Vortex Definition written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-04 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.Burley, Casey L. and Brooks, Thomas F. and vanderWall, Berend and Richard, Hughes and Raffel, Markus and Beaumier, Philippe and Delrieux, Yves and Lim, Joon W. and Yu, Yung H. and Tung, CheeAmes Research Center; Langley Research CenterROTOR AERODYNAMICS; VORTICES; WAKES; BO-105 HELICOPTER; ROTARY WINGS; WIND TUNNEL TESTS; PARTICLE IMAGE VELOCIMETRY; WIND TUNNELS; BLADE-VORTEX INTERACTION; BLADE SLAP NOISE
Author : Andrew Jue
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (142 download)
Download or read book Simulation of Advanced Rotorcraft Concepts Using Free Wake Aerodynamic Models written by Andrew Jue and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: An investigation of the flight dynamics of two different electric vertical takeoff and landing aircraft was performed using the Distributed Electric Propulsion Simulation (DEPSim). DEPSim incorporates a free-wake model that allows for prediction of aerodynamic interactions, so the use of DEPSim allows for investigation of the effects that aerodynamic interactions can have on flight dynamics. One of the two aircraft studied was a generic lift+cruise multicopter proposed for urban air mobility (UAM) use. The aircraft has four lift rotors in a quad configuration along with a wing, tail, and pusher propeller. The other aircraft studied was the Dragonfly octocopter planned for exploration of Saturn's moon Titan. It is a multicopter with four coaxial rotor pairs arranged in a quad configuration. For both aircraft, a variety of dynamic maneuvers were investigated. Specifically, for the lift+cruise aircraft, departure maneuvers and approach maneuvers were investigated. For these maneuvers, the flight dynamics were analyzed in addition to the power and energy consumption. The departure simulations, which compared different ways to transition to wing-borne flight, showed that the departure maneuver that reached wing-borne flight the quickest used the least energy, 58% of the energy of the maneuver that reached wing-borne flight the slowest. Additionally, significant rotor-wing interference was observed for this aircraft in both departure and approach maneuvers. This interference arises from changes in the effective angle of attack on the wing due to the induced velocity from the rotor wake. These angle of attack changes are correlated with the thrust differential of the front rotors and result in the generation of a rolling moment by the wings due to lift asymmetry. It was found that thrust differentials between the front two rotors resulted in a significant rolling moment that was close to 4 times the pusher propeller torque. A change in control allocation alleviated the problem and reduced the rolling moment. For the approach maneuvers, it was found that the effect of both the rolling moment from interference and the change in control allocation depended on the aircraft pitch during the maneuver. For Dragonfly, the transition to powered flight maneuver was investigated. Additionally, the dynamics of the aircraft were studied through the calculation of stability derivatives and linear models at hover, 1 m/s, 5 m/s, and 10.5 m/s. The transition to powered flight, along with select stability and control derivatives, were compared to reference data for verification. For the transition to powered flight, two separate versions were performed: one had the rotors running throughout the entire simulation while another included the rotor start-up component of the maneuver. Both maneuvers were able to track the reference data fairly well with predicted rear rotor speed and rotor thrust slightly higher than the reference data. Two versions of the stability and control derivatives were also generated. One version included wing struts in the model while the other did not, and a small impact on the results generated was seen due to the aerodynamic interference with the wing struts. Overall, the stability and control derivatives matched well with the reference data even with the different aerodynamic interactions. This shows decent verification of the reference data with the DEPSim aerodynamic model and the interactions the model captures.
Author : Wen Zhong Shen
Publisher : MDPI
ISBN 13 : 3039215248
Total Pages : 410 pages
Book Rating : 4.0/5 (392 download)
Download or read book Wind Turbine Aerodynamics written by Wen Zhong Shen and published by MDPI. This book was released on 2019-10-04 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wind turbine aerodynamics is one of the central subjects of wind turbine technology. To reduce the levelized cost of energy (LCOE), the size of a single wind turbine has been increased to 12 MW at present, with further increases expected in the near future. Big wind turbines and their associated wind farms have many advantages but also challenges. The typical effects are mainly related to the increase in Reynolds number and blade flexibility. This Special Issue is a collection of 21 important research works addressing the aerodynamic challenges appearing in such developments. The 21 research papers cover a wide range of problems related to wind turbine aerodynamics, which includes atmospheric turbulent flow modeling, wind turbine flow modeling, wind turbine design, wind turbine control, wind farm flow modeling in complex terrain, wind turbine noise modeling, vertical axis wind turbine, and offshore wind energy. Readers from all over the globe are expected to greatly benefit from this Special Issue collection regarding their own work and the goal of enabling the technological development of new environmentally friendly and cost-effective wind energy systems in order to reach the target of 100% energy use from renewable sources, worldwide, by 2050
Author : S. Gene Sadler
Publisher :
ISBN 13 :
Total Pages : 132 pages
Book Rating : 4.:/5 (31 download)
Download or read book Development and Application of a Method for Predicting Rotor Free Wake Positions and Resulting Rotor Blade Air Loads written by S. Gene Sadler and published by . This book was released on 1971 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rotor wake geometries are predicted by a process similar to the startup of a rotor in a free stream. An array of discrete trailing and shed vortices is generated with vortex strengths corresponding to stepwise radial and azimuthal blade circulations. The array of shed and trailing vortices is limited to an arbitrary number of azimuthal steps behind each blade. The remainder of the wake model of each blade is an arbitrary number of trailing vortices. Vortex element end points were allowed to be transported by the resultant velocity of the free stream and vortex-induced velocities. Wake geometry, wake flow, and wake-induced velocity influence coefficients are generated by this program for use in the blade loads portion of the calculations. Blade loads computations include the effects of nonuniform inflow due to a free wake, nonlinear airfoil characteristics, and response of flexible blades to the applied loads. Computed wake flows and blade loads are compared with experimentally measured data. Predicted blade loads, response and shears and moments are obtained for a model rotor system having two independent rotors. The effects of advance ratio, vertical separation of rotors, different blade radius ratios, and different azimuthal spacing of the blades of one rotor with respect to the other are investigated.
Author : Ritu Priyanka Marpu
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (858 download)
Download or read book Physics Based Prediction of Aeromechanical Loads for the UH-60A Rotor written by Ritu Priyanka Marpu and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Helicopters in forward flight experience complex aerodynamic phenomena to various degrees. In low speed level flight, the vortex wake remains close to the rotor disk and interacts with the rotor blades to give rise to blade vortex interaction phenomena. In high speed flight, compressibility effects dominate leading to the formation of shocks. If the required thrust is high, the combination of high collective pitch and cyclic pitch variations give rise to three-dimensional dynamic stall phenomena. Maneuvers further exacerbate the unsteady airloads and affect rotor and hub design. The strength and durability of the rotor blades and hub components is dependent on accurate estimates of peak-to-peak structural loads. Accurate knowledge of control loads is important for sizing the expensive swash-plate components and assuring long fatigue life. Over the last two decades, computational tools have been developed for modeling rotorcraft aeromechanics. In spite of this progress, loads prediction in unsteady maneuvers which is critical for peak design loads continues to be a challenging task. The primary goal of this research effort is to investigate important physical phenomena that cause severe loads on the rotor in steady flight and in extreme maneuvers. The present work utilizes a hybrid Navier-Stokes/free-wake CFD methodology coupled to a finite element based multi-body dynamics analysis to systematically study steady level and maneuvering flight conditions. Computational results are presented for the UH-60A rotor for a parametric sweep of speed and thrust conditions and correlated with test data at the NFAC Wind Tunnel. Good agreement with test data has been achieved using the current methodology for trim settings and integrated hub loads, torque, and power. Two severe diving turn maneuvers for the UH-60A recorded in the NASA/Army Airloads Flight Tests Database have also been investigated. These maneuvers are characterized by high load factors and high speed flight. The helicopter experiences significant vibration during these maneuvers. Mean and peak-to-peak structural loads and extensive stall phenomena including an advancing side stall phenomena have been captured by the present analyses.
Author : C. S. Chen
Publisher :
ISBN 13 :
Total Pages : 9 pages
Book Rating : 4.:/5 (227 download)
Download or read book Free-Wake Analysis of a Rotor in Hover written by C. S. Chen and published by . This book was released on 1987 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: A numerical method based on the axisymmetric, incompressible Navier-Stokes equations is combined with a lifting surface code to predict the vortex wake of hovering rotors. The lifting surface code, AMI Hover, is used to obtain the circulation distribution on the blade. This circulation distribution is fed into the Navier-Stokes code to compute the vortex wake under this specified circulation distribution. An iteration approach is used between these two codes to converge the circulation distribution and the shape of the vortex wake. A relaxation scheme is developed to resolve the instability encountered among the tip vortices. A reconcentration scheme is used to solve the diffusion problem due to the strong artificial viscosity. The results from the present method are compared with experimental data obtained by smoke-flow visualization and hot-wire measurements for several rotor blade configurations. The comparisons show that the present method is able to predict the complex wake system shed by a hovering rotor.
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.
