Download or read book A Simulation Model of Atmospheric Turbulence for Rotorcraft Applications written by Jamshed Riaz and published by . This book was released on 1992 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atmospheric Turbulence Simulation Techniques with Application to Flight Analysis written by Show-Tien Wang and published by . This book was released on 1980 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: Statistical modeling of atmospheric turbulence is discussed. The statistical properties of atmospheric turbulence, in particular the probability distribution, the spectra, and the coherence are reviewed. Different atmospheric turbulence simulation models are investigated, and appropriate statistical analyses are carried out to verify their validity. The models for simulation are incorporated into a computer model of aircraft flight dynamics. Statistical results of computer simulated landings for an aircraft having characteristics of a DC-8 are reported for the different turbulence simulation techniques. The significance of various degrees of sophistication in the turbulence simulation techniques on the landing performance of the aircraft is discussed.

Download or read book Modelling and Simulation of Gust and Atmospheric Turbulence Effects on Flexible Aircraft Flight Dynamics written by Pau Castells Marin and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The prediction of the aircraft response to gust and turbulence is of major importance for different purposes. Gust load analysis is an essential part of aircraft design and certification. The effect of gust and turbulence on aircraft flight dynamics is also of interest. Models able to capture relevant effects at these conditions in early design phases are essential in order to anticipate and assess the aircraft response and flight control laws in realistic atmospheric disturbances before flight test. This work proposes a modelling strategy to capture relevant physics when simulating the aircraft response to gust and turbulence for flight dynamics investigations. The model provides accuracy at a low computational cost as well as consistency with gust loads analysis enabling multidisciplinary design. The approach is based on the integration of a nonlinear quasi-steady flexible flight dynamics model with an unsteady aeroelastic model linearized around a nonlinear steady state. The gust-induced forces have a significant impact on aircraft flight dynamics. Low computing times are required to cover several flight conditions and aircraft parameters. A computationally efficient multipoint aerodynamic model, which captures both unsteady aerodynamic and gust propagation effects, is generated from linearized Computational Fluid Dynamics (CFD) simulations in the frequency domain. The model is identified through a rational function approximation allowing for time domain simulations. A reduced number of additional aerodynamic states is sufficient to capture the main effects at low frequencies for flight dynamics analysis. The impact of dynamic flexibility on the response is also evaluated. Only the most energetic flexible modes are retained to reduce the number of states and ensure a low computation time. The approach is applied to simulate the vertical and lateral response of a passenger aircraft to theoretical disturbance profiles as well as realistic atmospheric turbulence at different flight conditions. Aerodynamic nonlinear effects, such as local stalls due to shock motion, in transonic conditions may appear. The linearized model is able to capture the global aircraft response at these conditions with low amplitude shock motions. Results are compared and validated with a CFD simulation based approach, coupled with a structural dynamics and flight mechanics solver. Measures from flight test are also used to assess the modelling approach. The effect of uncertainties on the response is analysed, in terms of the turbulence variation along the wingspan. Simulation results show that relevant aerodynamic effects due to gust and turbulence are captured in the frequency range of interest for flight dynamics investigations.

Download or read book Development and Application of a Non gaussian Atmospheric Turbulence Model for Use in Flight Simulators written by and published by . This book was released on 1974 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 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.

Download or read book Helicopter Flight Dynamics written by Gareth D. Padfield and published by John Wiley & Sons. This book was released on 2018-11-19 with total page 858 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.

Download or read book Implementation and Testing of Turbulence Models for the F18 Harv Simulation written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-18 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents three methods of implementing the Dryden power spectral density model for atmospheric turbulence. Included are the equations which define the three methods and computer source code written in Advanced Continuous Simulation Language to implement the equations. Time-history plots and sample statistics of simulated turbulence results from executing the code in a test program are also presented. Power spectral densities were computed for sample sequences of turbulence and are plotted for comparison with the Dryden spectra. The three model implementations were installed in a nonlinear six-degree-of-freedom simulation of the High Alpha Research Vehicle airplane. Aircraft simulation responses to turbulence generated with the three implementations are presented as plots. Yeager, Jessie C. Langley Research Center TURBULENCE MODELS; ATMOSPHERIC TURBULENCE; ATMOSPHERIC MODELS; FLIGHT CHARACTERISTICS; AIRCRAFT PERFORMANCE; RESEARCH VEHICLES; DEGREES OF FREEDOM; SPECTRAL THEORY; COMPUTER PROGRAMS; NONLINEARITY...

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.

Download or read book Atmospheric turbulence and unsteady aerodynamics in aircraft simulation written by and published by . This book was released on 1985 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Investigation of Coupled Atmospheric Turbulence and Ship Airwakes for Helicopter ship Dynamic Interface Simulations written by Regis Santos Thedin and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The dynamic interface between a ship and a helicopter is a complex, hazardous environment, demanding high levels of pilot workload. In modeling & simulation of such environment for pilot training purposes, high levels of fidelity are required on the airwake module. The objectives of this research effort are two-fold. The first one is to analyze in details the effects of the turbulence present in the atmospheric boundary layer (ABL) on ships and the resulting airwake. The other objective is to use airwake data saved from the numerical simulations as external disturbances to a helicopter model in order to quantify an increase in pilot workload. Two different types of inflow are investigated: unsteady ABL and steady ABL. Unsteady cases are executed in OpenFOAM, are representatives of an actual stability state and include realistic features such as coherent structures. Steady ABL cases are executed in OVERFLOW and represent an appropriate velocity profile, but do not include any freestream turbulence. Uniform inflow cases are also executed on both codes as baseline cases. The SFS2 ship geometry is used and it is modeled by the immersed boundary method within OpenFOAM, while body-fitted overset grids are used in OVERFLOW. Pilot workload is quantified by a frequency-domain analysis of the energy associated with the usage of the input sticks.Initially, neutral cases with two levels of shear are investigated and compared to uniform inflow solutions. Analysis of velocity distributions along probe lines at the deck revealed that the presence of an ABL modifies the recirculation region and delays the reattachment point. Different levels of shear yield different characteristics. For airwakes modified by unsteady ABL inflow, spectral analysis at locations near the ship's flight deck indicated that higher energy content at frequencies above 3 Hz, with better agreement to Kolmogorov's -5/3 cascade, have been captured. Increased content has also been observed in the 0.1--0.3 Hz range. This energy cascade matches in situ experiments. Spectral content on the uniform inflow cases fails to match content above 3 Hz, which are also not usually captured in standard CFD simulations. The airwakes related to ABL inflows were not related to each other by a common factor, indicating that these solutions are not scalable, differently than what is usually observed for uniform inflows.Next, two hover locations outside of the airwake are considered, subject only to the turbulence present in the inflow -- in at an altitude of 20 ft and another at 80 ft. The ABL turbulence had a substantial effect on the vehicle, resulting in significantly more disturbances, considerably more power fluctuations, and fluctuations on the vehicle's attitudes. While this was observed on both cases, it was much more prominent in the high altitude case. The fluctuations were reflected on the stick usage, and thus pilot workload. The uniform inflow case barely exerted any effect and had comparable results to a scenario where only Pitt-Peters inflow model is used (no external disturbances). Analysis of the energy related to the stick usage showed that substantially more energy was found for the ABL case across all of the frequency range investigated for high altitude case, and a lower increase for the lower altitude case, found in the range of approximately 0.1--0.6 Hz. These results suggested that the large length-scale eddies that are present in the atmosphere seems to affect the vehicle and the pilot workload.Lastly, two hover locations at the flight deck have been investigated. The vehicle was subject to the highly turbulent air shedding off the superstructure and chimney. Comparisons between steady ABL, unsteady ABL, and uniform inflow are made. One hover location is within the highly separated region, and another is slightly higher. The second location represents a mix of the pure unsteady ABL flow and airwake turbulence. These locations were selected in order to check whether or not the effects from the atmospheric turbulence observed previously would apply here. For the unsteady ABL case, the results indicated that when the airwake turbulence dominates, an increase in the energy associated with frequencies in the range of 0.1--0.3 Hz has been observed. For frequencies above 0.5 Hz, not many differences are observed at the energy associated with the stick use. However, one of the main findings of this work is that when the aircraft was hovering only 10 ft higher, in a flowfield that was a mix of airwake and atmospheric turbulence, the energy associated with the unsteady ABL was higher than that associated with the uniform inflow for all of the 0.2--2 Hz spectrum. Now, with respect to the OVERFLOW's steady ABL case, no appreciable differences have been captured, in neither of the hover locations. The steady ABL approach did not affect the vehicle nearly as much as the unsteady ABL did. In fact, the uniform inflow consistently exhibited higher energy (although very small) than that seen under the steady ABL. The steady ABL did not add any relevant information.The results indicate that when the aircraft is flying at a location that is subject to more of the atmospheric eddies, the vehicle tends to react to the unsteadiness present, which represents additional pilot workload. This is especially relevant for a ship with a flat deck (similar to the LHA class). If the vehicle is solely in the wake of the superstructure, no relevant differences were observed. The lower fidelity approach of modeling the ABL as a steady ABL did not add any relevant pilot workload for the SFS2 with zero wind-over-deck case investigate.

Download or read book Journal of the American Helicopter Society written by American Helicopter Society and published by . This book was released on 2003 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Theory Methodology Tools and Applications for Modeling and Simulation of Complex Systems written by Lin Zhang and published by Springer. This book was released on 2016-09-21 with total page 660 pages. Available in PDF, EPUB and Kindle. Book excerpt: This four-volume set (CCIS 643, 644, 645, 646) constitutes the refereed proceedings of the 16th Asia Simulation Conference and the First Autumn Simulation Multi-Conference, AsiaSim / SCS AutumnSim 2016, held in Beijing, China, in October 2016. The 265 revised full papers presented were carefully reviewed and selected from 651 submissions. The papers in this third volume of the set are organized in topical sections on Cloud technologies in simulation applications; fractional calculus with applications and simulations; modeling and simulation for energy, environment and climate; SBA virtual prototyping engineering technology; simulation and Big Data.

Download or read book The Application of Invariant Modeling to the Calculation of Atmospheric Turbulence written by Coleman DuP. Donaldson and published by . This book was released on 1972 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atmospheric Turbulence written by Hans A. Panofsky and published by Wiley-Interscience. This book was released on 1984-02-03 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: New York : Wiley, c1984.

Download or read book Effects of Simulated Turbulence on Aircraft Handling Qualities written by Ira David Jacobson and published by . This book was released on 1977 with total page 206 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Modeling Turbulence for Flight Simulations at NASA Ames written by and published by . This book was released on 1975 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atmospheric Turbulence Modeling for Aero Vehicles Fractional Order Fits written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019-01-13 with total page 34 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric turbulence models are necessary for the design of both inlet/engine and flight controls, as well as for studying coupling between the propulsion and the vehicle structural dynamics for supersonic vehicles. Models based on the Kolmogorov spectrum have been previously utilized to model atmospheric turbulence. In this paper, a more accurate model is developed in its representative fractional order form, typical of atmospheric disturbances. This is accomplished by first scaling the Kolmogorov spectral to convert them into finite energy von Karman forms and then by deriving an explicit fractional circuit-filter type analog for this model. This circuit model is utilized to develop a generalized formulation in frequency domain to approximate the fractional order with the products of first order transfer functions, which enables accurate time domain simulations. The objective of this work is as follows. Given the parameters describing the conditions of atmospheric disturbances, and utilizing the derived formulations, directly compute the transfer function poles and zeros describing these disturbances for acoustic velocity, temperature, pressure, and density. Time domain simulations of representative atmospheric turbulence can then be developed by utilizing these computed transfer functions together with the disturbance frequencies of interest. Kopasakis, George Glenn Research Center NASA/TM-2010-216961, E-17566