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Book A Rotor Wake Model for Forward Flight Simulation Studies

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 Rotorcraft Simulation Model Enhancement to Support Land and Sea Based Testing and Operational Analysis

Download or read book Rotorcraft Simulation Model Enhancement to Support Land and Sea Based Testing and Operational Analysis written by and published by . This book was released on 1997 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study addresses model enhancements to rotor wake modeling that significantly improve the prediction of helicopter behavior across the flight envelope. Specifically, the model enhancements have been made to include the tip vortex distortion effect in the finite state dynamic wake model to improve the poor prediction of rotorcraft off-axis response. The enhanced formulation allows for better prediction of aerodynamic interference. This includes the rotor aerodynamic interference on fuselage and other lifting surfaces. A modification of the finite state dynamic wake model has also been made to include the vortex ring state. The resulting simulation is applicable across the flight envelope. The enhanced model has shown a remarkable improvement in the prediction of helicopter response in both hover and forward flight.

Book Helicopter Rotor Wake Geometry and Its Influence in Forward Flight Volume 1 Generalized Wake Geometry and Wake Effect on Rotor Airloads and Performance

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 Recent Rotor Wake Simulation and Modeling Studies at United Technologies Corporation

Download or read book Recent Rotor Wake Simulation and Modeling Studies at United Technologies Corporation written by T. Alan Egolf and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Rotor Wake Vortex Definition

    Rotor Wake Vortex Definition

    Book Details:
  • Author : National Aeronautics and Space Administration (NASA)
  • Publisher : Createspace Independent Publishing Platform
  • Release : 2018-06-04
  • ISBN : 9781720712114
  • Pages : 30 pages

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 A Model for the Wake geometry of the Lifting Rotor in Forward Flight

Download or read book A Model for the Wake geometry of the Lifting Rotor in Forward Flight written by Mukund Madhav Joglekar and published by . This book was released on 1969 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Book Simulation of Advanced Rotorcraft Concepts Using Free Wake Aerodynamic Models

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.

Book Numerical Simulation and Comparison of Symmetrical Supercritical Airfoils for the Near Tip Region of a Helicopter in Forward Flight

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...

Book Analytical Model of Rotor Wake Aerodynamics in Ground Effect

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:

Book Some Rotorcraft Applications of Computational Fluid Dynamics

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 Computation of Rotor Aerodynamic Loads in Forward Flight Using a Full Span Free Wake Analysis

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...