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A Study Of The Effects And Significance Of Transition Modeling For Rotorcraft Applications
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Book Synopsis A Study of the Effects and Significance of Transition Modeling for Rotorcraft Applications by : Ashwin Parwani
Download or read book A Study of the Effects and Significance of Transition Modeling for Rotorcraft Applications written by Ashwin Parwani and published by . This book was released on 2018 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: A four-blade helicopter rotor is modeled using computational fluid dynamics (CFD), and the impact on the flow-field with and without a floating fuselage geometry is assessed. The numerical predictions were made with CFD simulations using the NASA OVERFLOW 2.2n solver. For numerical simulations, the flow-field was discretized in a structured, overset topology with grids intended to solve the scope of the problem. Results based on a tip Mach number of 0.58 were acquired for various collective pitch angles. The simulations were completed with the Spalart-Allmaras (SA) one equation eddy-viscosity turbulence model along with the Spalart-Shur rotation/curvature correction coupled with the amplification factor transport (AFT) transition model. Additionally, Delayed, Detached Eddy Simulation (DDES) was used to induce hybrid RANS/LES behavior. Overall predicted figure of merit and laminar-to-turbulent transition patterns on the blade surfaces with and without the fuselage exhibited reasonable agreement with experimental data. Specifically, laminar-turbulent transition patterns on the blade surfaces at 10° collective pitch showed better agreement with experimental data than at 8° collective pitch. It was observed from the simulations that the blade root and tip vortex systems become increasingly unstable as the collective pitch is increased for both configurations.
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.
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 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Book Synopsis A Survey of Nonuniform Inflow Models for Rotorcraft Flight Dynamics and Control Applications by :
Download or read book A Survey of Nonuniform Inflow Models for Rotorcraft Flight Dynamics and Control Applications written by and published by . This book was released on 1989 with total page 70 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Applications of Pilot Modelling to Rotorcraft Flight Simulation Development by : Christopher Hendrick
Download or read book Applications of Pilot Modelling to Rotorcraft Flight Simulation Development written by Christopher Hendrick and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The behavior and capability of the human pilot is central to the development of manned aviation vehicles. Thus, mathematical models of the human pilot are desirable for a multitude of applications, several of which are explored in this thesis. The first application discussed here is the study of pilot utilization of motion cues. Understanding how pilot control behavior changes with motion cue magnitude is crucial to optimizing motion cueing algorithms, especially when using smaller motion systems with limited leg travel. For this purpose, a single-axis sum of sines (SOS) tracking task was conducted with a simple transfer function aircraft model, with the magnitude of motion cues varied from test to test. A hybrid particle swarm Levenberg-Marquardt-Fletcher (PS-LMF) identification algorithm is developed, and pilot models are extracted from test data in order to study changes in pilot control behavior. The second application is the study of aircraft handling qualities. Chapter 2 gives a brief study of the correlation between identified pilot model parameters and handling qualities ratings (HQRs) to show the potential for applying physiological measurements to HQR assessment. In these tests, a full nonlinear simulation model of a compound rotorcraft with a dynamic inversion controller is used in a SOS tracking task. The aircraft controller bandwidth is varied to provide different handling qualities and the PS-LMF algorithm is used to identify pilot model parameters. The third application is flight simulation development, where a reliable pilot model can be of value for a variety of reasons. Such reasons include expediting development due to a reduced reliance on piloted simulation tests, prediction of pilot workload, reduced cost, and the generation of reproducible results. For this purpose, a pilot model is developed for a multi-axis hover task, where the pilot is attempting to hold a hover in a turbulent airwake. This task is of interest as it is representative of the dynamic interface problem, which refers to the turbulent conditions experienced in near ship operation of rotorcraft. The model is developed through an inverse dynamics technique and nonlinear elements are added in the collective and pedal input channels. The results are compared to flight test data, and the model shows potential as a valuable development tool.
Book Synopsis Band-pass Shock and Vibration Absorbers for Application to Aircraft Landing Gear by : Emanuel Schnitzer
Download or read book Band-pass Shock and Vibration Absorbers for Application to Aircraft Landing Gear written by Emanuel Schnitzer and published by . This book was released on 1956 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new class of frequency-selective shock absorbers called band-pass shock absorbers which were conceived as a means of overcoming some of the limitations of conventional shock absorbers is described. These shock absorber designs are introduced, special emphasis being given to their use in landing and taxiing problems of high-speed aircraft. For such aircraft operated on rough land or water runways, conventional oleo struts approach a rigid condition for bum[s with steep slopes and thereby develop and transmit severe shock loads to the aircraft fuselage. The operation of the band-pass shock absorbers in the reduction of loads in certain selected frequency ranges is described. Theoretical equations are derived and solutions are made for several cases for the purpose of comparing the low-pass and conventional shock-absorber actions. The results indicate that the band-pass shock absorbers should alleviate high-frequency or rapidly applied impact loads but should retain the characteristics of conventional oleo struts when taxiing and design landing loads are slowly applied. A number of variations in design are presented for low-pass shock absorbers and reference is made to double-acting band-pass vibration absorbers for other applications.
Book Synopsis A Review of NASA Lewis' Development Plans for Computational Simulation of Aircraft Icing by : Mark G. Potapczuk
Download or read book A Review of NASA Lewis' Development Plans for Computational Simulation of Aircraft Icing written by Mark G. Potapczuk and published by . This book was released on 1999 with total page 22 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Flight Control Design for Rotorcraft with Variable Rotor Speed by : Wei Guo
Download or read book Flight Control Design for Rotorcraft with Variable Rotor Speed written by Wei Guo and published by . This book was released on 2009 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flight control design issues for rotorcraft with variable rotor speed are investigated, and new design methodologies are developed to deal with the challenges of variable rotor speed. The benefits of using variable rotor speed for rotorcraft are explored with a rotor speed optimization study using a modified GENHEL model of UH-60A Blackhawk. The optimization results recommend to use the optimal rotor speed in each flight condition to improve the helicopter performance. The efforts are made to accommodate the optimal rotor speed schedule into the flight control system design and also address the stability issues due to the rotor speed variation. The rotor speed optimization results show significant performance improvements can be achieved with moderate reductions in rotor speed. The objective of the control design is to accommodate these rotor speed variations, while achieving desired flying qualities and maneuver performance. A gain scheduled model following/model inversion controller is used to control the roll, pitch, yaw, heave, and rotor speed degrees of freedom. Rotor speed is treated as a redundant control effector for the heave axis, and different control allocation schemes are investigated. The controllers are evaluated based on step responses and the ADS-33E height response requirement. Results show that dynamic variation in rotor speed can improve maximum climb rate and flying qualities for moderate to large commands in vertical speed, but that non-linear effects present significant challenges when integrating control of the aircraft and the engine. The effects of reduced rotor speeds on stability margins, torque required, and stability issues are also studied. A power command system in the vertical axis is designed to incorporate variable rotor speed while handling torque limits and other constraints. The vertical axis controller uses a fixed nonlinear mapping to find the combination of collective pitch and rotor speed to optimize performance in level flight, climbing/descending flight, and steady turns. In this scheme, the controller is open-loop, making it an inexpensive and reliable solution. The mapping is designed to produce a desired power level for a given pilot input. Thus the mapping can take into account the performance limits associated with the vertical axis such as power limits, torque limits, and maximum rate of descent. A model following controller is implemented for the pitch, roll, and yaw axes. The piloted simulation was performed to evaluate the controller. The impact of variable rotor speed on closed loop stability of rotorcraft is discussed. The model following controller can provide high bandwidth control and improve performance using variable rotor speed. However, reduction of rotor speed can result in rotor body coupling and even instability. A rotor state feedback control law can be designed independently and easily integrated into the baseline model following control architecture. Simulations were performed to verify the effectiveness of RSF control to stabilize the rotorcraft dynamics or improve the command tracking performance in the presence of reduced rotor RPM.
Book Synopsis International Aerospace Abstracts by :
Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 920 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development Publisher : ISBN 13 : Total Pages :274 pages Book Rating :4.:/5 (15 download)
Book Synopsis Impact of military applications on rotorcraft and V/STOL aircraft design by : North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development
Download or read book Impact of military applications on rotorcraft and V/STOL aircraft design written by North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development and published by . This book was released on 1981 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Journal of the American Helicopter Society by : American Helicopter Society
Download or read book Journal of the American Helicopter Society written by American Helicopter Society and published by . This book was released on 1993 with total page 722 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Technical Memorandum written by and published by . This book was released on 1984 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. Congress. House. Committee on Armed Services. Subcommittee on Military Installations and Facilities Publisher : ISBN 13 : Total Pages :954 pages Book Rating :4.F/5 ( download)
Book Synopsis Hearings on H.R. 11833 [H.R. 12384]--to authorize certain construction at military installations, and for other purposes by : United States. Congress. House. Committee on Armed Services. Subcommittee on Military Installations and Facilities
Download or read book Hearings on H.R. 11833 [H.R. 12384]--to authorize certain construction at military installations, and for other purposes written by United States. Congress. House. Committee on Armed Services. Subcommittee on Military Installations and Facilities and published by . This book was released on 1976 with total page 954 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :United States. Congress. House. Committee on Armed Services. Subcommittee on Military Installations and Facilities Publisher : ISBN 13 : Total Pages :676 pages Book Rating :4.0/5 (18 download)
Book Synopsis Hearings on H.R. 11833 [H.R. 12384] to Authorize Certain Construction at Military Installations, and for Other Purposes, Before Subcommittee on Military Installations and Facilities of the Committee on Armed Services, House of Representatives, Ninety-fourth Congress, Second Session .... by : United States. Congress. House. Committee on Armed Services. Subcommittee on Military Installations and Facilities
Download or read book Hearings on H.R. 11833 [H.R. 12384] to Authorize Certain Construction at Military Installations, and for Other Purposes, Before Subcommittee on Military Installations and Facilities of the Committee on Armed Services, House of Representatives, Ninety-fourth Congress, Second Session .... written by United States. Congress. House. Committee on Armed Services. Subcommittee on Military Installations and Facilities and published by . This book was released on 1976 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development Publisher : ISBN 13 : Total Pages :614 pages Book Rating :4.3/5 (243 download)
Book Synopsis AGARD Index of Publications by : North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development
Download or read book AGARD Index of Publications written by North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development and published by . This book was released on 1995 with total page 614 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Cumulative Computer Abstracts: Computer applications: CU artificial intelligence; CV linguistics, textual data processing and the liberal arts; CW life science and engineering; CX physical science and engineering; CY control engineering; CZ management, gevernment and education by : Geoffrey Knight
Download or read book Cumulative Computer Abstracts: Computer applications: CU artificial intelligence; CV linguistics, textual data processing and the liberal arts; CW life science and engineering; CX physical science and engineering; CY control engineering; CZ management, gevernment and education written by Geoffrey Knight and published by . This book was released on 1969 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Aeronautical Engineering: A Cumulative Index to a Continuing Bibliography (supplement 261) by :
Download or read book Aeronautical Engineering: A Cumulative Index to a Continuing Bibliography (supplement 261) written by and published by . This book was released on 1991 with total page 566 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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