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A Rotor Wake Model For Forward Flight Simulation Studies
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Book Synopsis A Rotor Wake Model for Forward Flight Simulation Studies by : K. R. Reddy
Download or read book A Rotor Wake Model for Forward Flight Simulation Studies written by K. R. Reddy and published by . This book was released on 1981 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Note presents an attempt to develop a rotor wake model for forward flight which requires only modest computing time and, therefore, is suitable for flight simulation studies. Free and rigid wake models are discussed, together with various simplifying assumptions, in order to reduce the computation time to acceptable levels for simulation studies. Using a tip vortex wake model and the Biot-Savart relation, induced velocities are calculated in the rotor plane. It is then assumed that the tip vortex wake takes the form of a skewed helix. Such a simple prescribed model requires little computing time and the accuracy of its results when compared with more elaborate free wake models shows considerable promise. (Author).
Book Synopsis Helicopter Rotor Wake Geometry and Its Influence in Forward Flight. Volume 1: Generalized Wake Geometry and Wake Effect on Rotor Airloads and Performance by : T. A. Egolf
Download or read book Helicopter Rotor Wake Geometry and Its Influence in Forward Flight. Volume 1: Generalized Wake Geometry and Wake Effect on Rotor Airloads and Performance written by T. A. Egolf and published by . This book was released on 1983 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analytic investigation to generalize wake geometry of a helicopter rotor in steady level forward flight and to demonstrate the influence of wake deformation in the prediction of rotor airloads and performance is described. Volume 1 presents a first level generalized wake model based on theoretically predicted tip vortex geometries for a selected representative blade design. The tip vortex distortions are generalized in equation form as displacements from the classical undistorted tip vortex geometry in terms of vortex age, blade azimuth, rotor advance ratio, thrust coefficient, and number of blades. These equations were programmed to provide distorted wake coordinates at very low cost for use in rotor airflow and airloads prediction analyses. The sensitivity of predicted rotor airloads, performance, and blade bending moments to the modeling of the tip vortex distortion are demonstrated for low to moderately high advance ratios for a representative rotor and the H-34 rotor. Comparisons with H-34 rotor test data demonstrate the effects of the classical, predicted distorted, and the newly developed generalized wake models on airloads and blade bending moments. Use of distorted wake models results in the occurrence of numerous blade-vortex interactions on the forward and lateral sides of the rotor disk. The significance of these interactions is related to the number and degree of proximity to the blades of the tip vortices. The correlation obtained with the distorted wake models (generalized and predicted) is encouraging.
Book Synopsis Simulation of Advanced Rotorcraft Concepts Using Free Wake Aerodynamic Models by : Andrew Jue
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 :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)
Book Synopsis Numerical Simulation and Comparison of Symmetrical/Supercritical Airfoils for the Near Tip Region of a Helicopter in Forward Flight by : National Aeronautics and Space Administration (NASA)
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 :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)
Book Synopsis Rotor Wake Vortex Definition by : National Aeronautics and Space Administration (NASA)
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
Book Synopsis Experimental Evaluation of a Flat Wake Theory for Predicting Rotor Inflow-wake Velocities by : John C. Wilson
Download or read book Experimental Evaluation of a Flat Wake Theory for Predicting Rotor Inflow-wake Velocities written by John C. Wilson and published by . This book was released on 1992 with total page 62 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Helicopter Flight Dynamics by : Gareth D. Padfield
Download or read book Helicopter Flight Dynamics written by Gareth D. Padfield and published by John Wiley & Sons. This book was released on 2018-09-07 with total page 856 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Book The behaviour of helicopters and tiltrotor aircraft is so complex that understanding the physical mechanisms at work in trim, stability and response, and thus the prediction of Flying Qualities, requires a framework of analytical and numerical modelling and simulation. Good Flying Qualities are vital for ensuring that mission performance is achievable with safety and, in the first and second editions of Helicopter Flight Dynamics, a comprehensive treatment of design criteria was presented, relating to both normal and degraded Flying Qualities. Fully embracing the consequences of Degraded Flying Qualities during the design phase will contribute positively to safety. In this third edition, two new Chapters are included. Chapter 9 takes the reader on a journey from the origins of the story of Flying Qualities, tracing key contributions to the developing maturity and to the current position. Chapter 10 provides a comprehensive treatment of the Flight Dynamics of tiltrotor aircraft; informed by research activities and the limited data on operational aircraft. Many of the unique behavioural characteristics of tiltrotors are revealed for the first time in this book. The accurate prediction and assessment of Flying Qualities draws on the modelling and simulation discipline on the one hand and testing practice on the other. Checking predictions in flight requires clearly defined mission tasks, derived from realistic performance requirements. High fidelity simulations also form the basis for the design of stability and control augmentation systems, essential for conferring Level 1 Flying Qualities. The integrated description of flight dynamic modelling, simulation and flying qualities of rotorcraft forms the subject of this book, which will be of interest to engineers practising and honing their skills in research laboratories, academia and manufacturing industries, test pilots and flight test engineers, and as a reference for graduate and postgraduate students in aerospace engineering.
Book Synopsis Government Reports Announcements & Index by :
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1989-05 with total page 800 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Department of the army by : United States. Congress. Senate. Committee on Appropriations
Download or read book Department of the army written by United States. Congress. Senate. Committee on Appropriations and published by . This book was released on 1971 with total page 1562 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Scientific and Technical Aerospace Reports by :
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Technical Abstract Bulletin written by and published by . This book was released on 1982 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Helicopter Rotor Wake Geometry and Its Influence in Forward Flight. Volume 2: Wake Geometry Charts by : T. Alan Egolf
Download or read book Helicopter Rotor Wake Geometry and Its Influence in Forward Flight. Volume 2: Wake Geometry Charts written by T. Alan Egolf and published by . This book was released on 1983 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Principles of Helicopter Aerodynamics with CD Extra by : Gordon J. Leishman
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 Synopsis Some Rotorcraft Applications of Computational Fluid Dynamics by :
Download or read book Some Rotorcraft Applications of Computational Fluid Dynamics written by and published by . This book was released on 1988 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: The growing application of computational aerodynamics to nonlinear rotorcraft problems is outlined, with particular emphasis on the development of new methods based on Euler and thin-layer Navier-Stokes equations. Rotor airfoil characteristics can now be calculated accurately over a wide range of transonic flow conditions. However, unsteady three-dimensional viscous codes remain in the research stage, and a numerical simulation of the complete flow field about a helicopter in forward flight is not currently feasbile. Nevertheless, impressive progress is being made in preparation for future supercomputers that will enable meaningful calculations to be made for arbitrary rotorcraft configurations. (fr).
Book Synopsis Helicopter Rotor Wake Geometry and Its Influence in Forward Flight by : T. Alan Egolf
Download or read book Helicopter Rotor Wake Geometry and Its Influence in Forward Flight written by T. Alan Egolf and published by . This book was released on 1983 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Helicopter Rotor Noise Due to Ingestion of Atmospheric Turbulence by : John C. Simonich
Download or read book Helicopter Rotor Noise Due to Ingestion of Atmospheric Turbulence written by John C. Simonich and published by . This book was released on 1986 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt: A theoretical study was conducted to develop an analytical prediction method for helicopter main rotor noise due to the ingestion of atmospheric turbulence. This study incorporates an atmospheric turbulence model, a rotor mean flow contraction model and a rapid distortion turbulence model which together determine the statistics of the non-isotropic turbulence at the rotor plane. Inputs to the combined mean inflow and turbulence models are controlled by atmospheric wind characteristics and helicopter operating conditions. A generalized acoustic source model was used to predict the far field noise generated by the non-isotropic flow incident on the rotor. Absolute levels for acoustic spectra and directivity patterns were calculated for full scale helicopters, without the use of empirical or adjustable constants. Comparisons between isotropic and non-isotropic turbulence at the rotor face demonstrated pronounced differences in acoustic spectra. Turning and contraction of the flow for hover and low speed vertical ascent cases result in a 3 dB increase in the acoustic spectrum energy and a 10 dB increase in tone levels. Compared to trailing edge noise, turbulence ingestion noise is the dominant noise mechanism below approximately 30 rotor harmonics, while above 100 harmonics, trailing edge noise levels exceed turbulence ingestion noise by 25 dB.
Book Synopsis Finite Difference Modeling of Rotor Flows Including Wake Effects by :
Download or read book Finite Difference Modeling of Rotor Flows Including Wake Effects written by and published by . This book was released on 1982 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper gives a brief consideration of rotary wing finite difference methods. The main concern is the specification of boundary conditions to properly account for the effect of the wake on the blade. Examples are given of an approach where wake effects are introduced by specifying an equivalent angle of attack. An alternate approach is also given where discrete vortices are introduced into the finite difference grid. The resulting computations of hovering and high advance-ratio cases compare well with experiment. Some consideration is also given to the modeling of low-to-moderate advance-ratio flows. (Author).
