Development Of An Unsteady Aero Elastic Framework For The Study Of A Slotted Natural Laminar Flow Airfoil
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Development Of An Unsteady Aero Elastic Framework For The Study Of A Slotted Natural Laminar Flow Airfoil
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Author : Auriane Bottai
language : en
Publisher:
Release Date : 2023
Development Of An Unsteady Aero Elastic Framework For The Study Of A Slotted Natural Laminar Flow Airfoil written by Auriane Bottai and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
The objective of this research is to develop a framework for the study of the aero-elastic behavior of a truss-braced, Slotted, Natural-Laminar Flow (SNLF) wing. This type of airfoil emerged in the 2010s as a solution to significantly increase the lift coefficient while reducing the overall drag. It is composed of two encapsulated airfoils, separated by a small gap, or slot. Unlike an airfoil equipped with a flap, the aft element of such airfoil remains fixed. The aft element alleviates the pressure recovery requirement at the trailing edge of the fore element, thereby significantly extending the laminar flow region on the fore element. On the other hand, truss braced wings typically have longer span than conventional wings, which drives down the induced drag of the overall aircraft. This is permitted by the truss which adds structural reinforcement and alleviates the larger root bending moment arising from the longer span configuration. Earlier studies have found that combining those technologies for a new wing design has the potential of drastically reducing commercial aircraft fuel consumption. The present work is composed of fours parts: the first part consists of developing of an aero-elastic framework capable of predicting the aero-elastic stability of the wing. This tool is developed in time domain and proceeds by calculating the eigenvalues of the aero-elastic system. The signs of the real part of those eigenvalues determines whether the structure is stable or not. This tool is tested and validated on a classic wing configuration, the Goland wing. The second part is dedicated to the modal analysis and static stability of the \acl{snlf} wing. For this purpose, a \acl{fem} of the wing is developed. Connectors between the two airfoils are added in the geometry to maintain the profile integrity under external loading. Modal analysis with a various number of connectors showed that 13 or more connectors lead to similar mode shapes but the more connectors, the higher the natural frequencies. Fewer connectors result in significant wing deformation and deformation of the airfoil profile. \par The initial aero-elastic tool developed in this work models the two-element wing as two rectangular wings with no inter-element aerodynamic coupling. This weakness is overcome by an extensive steady flow analysis of the baseline Slotted, Natural-Laminar Flow airfoil as well as six deformed configurations in which the aft element is slightly moved upstream, downstream, upwards, downwards and rotated. This steady analysis showed that the contraction or dilatation of the gap can significantly affect the airfoil performance.Those effects are aggravated with increased Mach numbers and/or higher angle-of-attack. Conversely, if the aft element is rotated in a way that preserves the gap width, the aerodynamic coefficients remain nearly unchanged. The results of this sensitivity study are next integrated in the initially aero-elastic framework to study the aerodynamic stability of the \acl{snlf} wing, with various number of connectors. It is found that at least 13 connectors are needed to remain in the linear regime of variations of the aerodynamic coefficients. This is also the minimum number of connectors for the wing to remain stable. Finally, the behavior of the Slotted, Natural-Laminar Flow airfoil under unsteady circumstances is analyzed via a singularity based, Lagrangian method. Linear-varying strength vortex elements are distributed on the airfoil and complemented with other types of discrete singularities. The later enables corrections to the pressure coefficient and thereby the lift and moment coefficients and match the steady state loads predicted by a higher resolution flow solver. Unsteady aerodynamic coefficients up to a reduced frequency of unity of the Slotted, Natural-Laminar Flow wing with respect to vertical, chord-wise and rotational displacements of the fore and aft elements are generated with the linear-varying strength vortex method. The unsteady procedure with corrective singularities is tested on a symmetric thin airfoil and provides encouraging results. The corrective singularities are found to successfully correct the mean values of the lift coefficient but also affect the amplitude of lift and moment oscillations.
Aerodynamic Design And Analysis For A Strut Braced Transport Aircraft Utilizing Slotted Natural Laminar Flow Airfoils
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Author : Leonard P. Metkowski
language : en
Publisher:
Release Date : 2023
Aerodynamic Design And Analysis For A Strut Braced Transport Aircraft Utilizing Slotted Natural Laminar Flow Airfoils written by Leonard P. Metkowski and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
This thesis performs a design study exploring the aerodynamic design of a strut-braced transport aircraft. Moving from classical lifting-line theory to modern Reynolds Averaged Navier Stokes methods, several design and analysis methods are used to better understand this configuration, which is designed to meet NASA's N+4 commuter transport goals. The use of a novel slotted airfoil, the S207, is incorporated from the start. Intended to achieve long runs of laminar flow, this airfoil was designed along with the strut-braced configuration presented in this work. Analysis of both the airfoil's sectional characteristics and its application to the planform are explored. Several other areas researched include the use of a lifting strut verses an aerodynamically feathered strut and the design of winglets on the high-span aircraft. The aerodynamically feathered strut is chosen for the configuration at hand, while winglets are predicted by classical methods to add approximately 3% to maximum efficiency. The configuration is further analyzed with the modern computational fluid dynamic solver, OVERFLOW. This Reynolds Averaged Navier-Stokes solver is coupled with the Amplification-Factor-Transport transition model for transonic laminar flow prediction. Several performance differences with both the two-dimensional airfoil, and three-dimensional configuration are quantified. For two-dimensional cruise cases, Euler methods predict approximately 15 counts less profile drag when compared to the Reynolds Averaged method. Increases in profile drag that are found in the Reynolds Averaged models are attributed to early transition on the airfoil fore-element. The Euler methods also show transition to move slowly forward on the upper surface at increasing angles of attack. In comparison, the RANS method has transition move rather rapidly forward, limiting the upper corner of the low-drag region. Three-dimensional comparisons include highlighting problem areas around the strut/wing juncture, along with differences in spanwise lift distributions due to the addition of winglets. Further discussion on the sectional pressure distributions and the resulting two-dimensionality of the flow on the slotted configuration due to the winglet is also presented. Overall efficiency gains predicted by RANS with the addition of the winglet is found to be approximately 5%.
Scientific And Technical Aerospace Reports
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Author :
language : en
Publisher:
Release Date : 1987
Scientific And Technical Aerospace Reports written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1987 with Aeronautics categories.
An Experimental And Computational Investigation Of Oscillating Airfoil Unsteady Aerodynamics At Large Mean Incidence
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Author : National Aeronautics and Space Administration (NASA)
language : en
Publisher: Createspace Independent Publishing Platform
Release Date : 2018-08-27
An Experimental And Computational Investigation Of Oscillating Airfoil Unsteady Aerodynamics At Large Mean Incidence written by National Aeronautics and Space Administration (NASA) and has been published by Createspace Independent Publishing Platform this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-08-27 with categories.
A major challenge in the design and development of turbomachine airfoils for gas turbine engines is high cycle fatigue failures due to flutter and aerodynamically induced forced vibrations. In order to predict the aeroelastic response of gas turbine airfoils early in the design phase, accurate unsteady aerodynamic models are required. However, accurate predictions of flutter and forced vibration stress at all operating conditions have remained elusive. The overall objectives of this research program are to develop a transition model suitable for unsteady separated flow and quantify the effects of transition on airfoil steady and unsteady aerodynamics for attached and separated flow using this model. Furthermore, the capability of current state-of-the-art unsteady aerodynamic models to predict the oscillating airfoil response of compressor airfoils over a range of realistic reduced frequencies, Mach numbers, and loading levels will be evaluated through correlation with benchmark data. This comprehensive evaluation will assess the assumptions used in unsteady aerodynamic models. The results of this evaluation can be used to direct improvement of current models and the development of future models. The transition modeling effort will also make strides in improving predictions of steady flow performance of fan and compressor blades at off-design conditions. This report summarizes the progress and results obtained in the first year of this program. These include: installation and verification of the operation of the parallel version of TURBO; the grid generation and initiation of steady flow simulations of the NASA/Pratt&Whitney airfoil at a Mach number of 0.5 and chordal incidence angles of 0 and 10 deg.; and the investigation of the prediction of laminar separation bubbles on a NACA 0012 airfoil.Capece, Vincent R. and Platzer, Max F.Glenn Research CenterUNSTEADY AERODYNAMICS; TURBOMACHINERY; AIRFOILS; AEROELASTICITY; GAS TURBINE ENGINES; INCIDENCE; FORCED VIBRATION...
A Modern Course In Aeroelasticity
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Author : Robert Clark
language : en
Publisher: Springer Science & Business Media
Release Date : 2006-01-24
A Modern Course In Aeroelasticity written by Robert Clark and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006-01-24 with Technology & Engineering categories.
In this new edition, the fundamental material on classical linear aeroelasticity has been revised. Also new material has been added describing recent results on the research frontiers dealing with nonlinear aeroelasticity as well as major advances in the modelling of unsteady aerodynamic flows using the methods of computational fluid dynamics and reduced order modeling techniques. New chapters on aeroelasticity in turbomachinery and aeroelasticity and the latter chapters for a more advanced course, a graduate seminar or as a reference source for an entrée to the research literature.
Unsteady Aerodynamics Of Airfoils And Characterization And Modeling Of Axisymmetric Synthetic Jets
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Author : Xi Xia
language : en
Publisher:
Release Date : 2018-11-29
Unsteady Aerodynamics Of Airfoils And Characterization And Modeling Of Axisymmetric Synthetic Jets written by Xi Xia and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-11-29 with Technology & Engineering categories.
Abstract: This thesis has two main parts. The aerodynamic part is motivated by the interest in unveiling the flying secrets of natural fliers, e.g. birds and insects. The understandings will provide insights in the design and control of micro air vehicles (MAVs) for improved aerodynamic performance. The second part of the thesis focuses on the study of synthetic jets for aerodynamic flow control over MAVs. This is motivated by the promising effects of synthetic jets in enhancing mixing and controlling flow separation. The thesis starts with the unsteady aerodynamic modeling of a flat plate based on the Joukowski transformation and vortex method. The analytical solution includes both translational and rotational motions of the flat plate. The force calculation suggests that the lift generation caused by a stabilized leading edge vortex is a combined effect of the motions of both leading-edge and trailing-edge vortices. To extend this model to an arbitrarily-shaped airfoil, the wall boundary condition on the airfoil is enforced by introducing a bound vortex sheet at the location of the airfoil boundary. Furthermore, an analytical vortex-sheet formation condition is proposed to accurately evolve the wake vortices, and is based on the conservation laws of mass and momentum as well as Kelvin's circulation theorem. This condition resolves the paradox of the Giesing-Maskell model, which does not recover the steady-state Kutta condition. The thesis continues with an investigation of synthetic jets in a quiescent environment. An effective-eddy-viscosity concept is adopted to provide a unified modeling approach for the entrainment and mixing of any round jet, continuous or synthetic. The experimental study is focused on characterizing the spreading and decay features in the transitional region and far field of synthetic jets. The far-field momentum flux of a synthetic jet is modeled by calculating the hydrodynamic impulse of the vortical structure formed in the near field. Synthetic jets issuing into a crossflow are also studied and a self-similar model is developed for the trajectory and velocity of the midplane flow field. It is found that the crossflow velocity is enhanced in the near field due to the induced effect of the tilted vortex rings. This finding provides an auxiliary explanation for the mechanism of a synthetic jet in flow-separation control. Dissertation Discovery Company and University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Unsteady Aerodynamics of Airfoils and Characterization and Modeling of Axisymmetric Synthetic Jets" by Xi Xia, was obtained from University of Florida and is being sold with permission from the author. A digital copy of this work may also be found in the university's institutional repository, IR@UF. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation.
Analysis Of Low Speed Unsteady Airfoil Flows
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Author : Tuncer Cebeci
language : en
Publisher: Springer
Release Date : 2014-11-16
Analysis Of Low Speed Unsteady Airfoil Flows written by Tuncer Cebeci and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-11-16 with Technology & Engineering categories.
The standard textbooks on aerodynamics usually omit any discussion of un steady aerodynamics or, at most, consider it only in a single chapter, based on two justifications. The first is that unsteady aerodynamics should be regarded as a specialized subject required "only" in connection with understanding and an alyzing aeroelastic phenomena such as flutter and gust response, and therefore should be dealt with in related specialist books. The second reason appears to be reluctance to discuss aerodynamics with the inclusion of the time-dependent terms in the conservation equations and the boundary conditions for fear that added complications may discourage the reader. We take the opposite view in this book and argue that a full understanding of the physics of lift generation is possible only by considering the unsteady aerody namics of the starting vortex generation process. Furthermore, certain "steady" flows are inherently unsteady in the presence of flow separation, as for example the unsteady flow caused by the Karman vortex shedding downstream of a cylin der and "static" airfoil stall which is an inherently unsteady flow phenomenon. Therefore, it stands to reason that a unified treatment of aerodynamics that yields steady-state aerodynamics as a special case offers advantages. This rea soning is strengthened by the developments in computational fluid dynamics over the past forty years, which showed that accurate steady-state solutions can be obtained efficiently by solving the unsteady flow equations.
Introduction To Nonlinear Aeroelasticity
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Author : Grigorios Dimitriadis
language : en
Publisher: John Wiley & Sons
Release Date : 2017-03-10
Introduction To Nonlinear Aeroelasticity written by Grigorios Dimitriadis and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-03-10 with Technology & Engineering categories.
Introduction to Nonlinear Aeroelasticity Introduces the latest developments and technologies in the area of nonlinear aeroelasticity Nonlinear aeroelasticity has become an increasingly popular research area in recent years. There have been many driving forces behind this development, increasingly flexible structures, nonlinear control laws, materials with nonlinear characteristics and so on. Introduction to Nonlinear Aeroelasticity covers the theoretical basics in nonlinear aeroelasticity and applies the theory to practical problems. As nonlinear aeroelasticity is a combined topic, necessitating expertise from different areas, the book introduces methodologies from a variety of disciplines such as nonlinear dynamics, bifurcation analysis, unsteady aerodynamics, non-smooth systems and others. The emphasis throughout is on the practical application of the theories and methods, so as to enable the reader to apply their newly acquired knowledge Key features: Covers the major topics in nonlinear aeroelasticity, from the galloping of cables to supersonic panel flutter Discusses nonlinear dynamics, bifurcation analysis, numerical continuation, unsteady aerodynamics and non-smooth systems Considers the practical application of the theories and methods Covers nonlinear dynamics, bifurcation analysis and numerical methods Accompanied by a website hosting Matlab code Introduction to Nonlinear Aeroelasticity is a comprehensive reference for researchers and workers in industry and is also a useful introduction to the subject for graduate and undergraduate students across engineering disciplines.
Principles Of Aeroelasticity
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Author : Rama B. Bhat
language : en
Publisher: CRC Press
Release Date : 2016-04-27
Principles Of Aeroelasticity written by Rama B. Bhat and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-04-27 with Science categories.
Introductory Guide on the Design of Aerospace Structures Developed from a course taught at Concordia University for more than 20 years, Principles of Aeroelasticity utilizes the author’s extensive teaching experience to immerse undergraduate and first-year graduate students into this very specialized subject. Ideal for coursework or self-study, this detailed examination introduces the concepts of aeroelasticity, describes how aircraft lift structures behave when subjected to aerodynamic loads, and finds its application in aerospace, civil, and mechanical engineering. The book begins with a discussion on static behavior, and moves on to static instability and divergence, dynamic behavior leading up to flutter, and fluid structure interaction problems. It covers classical approaches based on low-order aerodynamic models and provides a rationale for adopting certain aeroelastic models. The author describes the formulation of discrete models as well as continuous structural models. He also provides approximate methods for solving divergence, flutter, response and stability of structures, and addresses non-aeroelastic problems in other areas that are similar to aeroelastic problems. Topics covered include: The fundamentals of vibration theory Vibration of single degree of freedom and two degrees of freedom systems Elasticity in the form of an idealized spring element Repetitive motion Flutter phenomenon Classical methods, Rayleigh-Ritz techniques, Galerkin’s technique, influential coefficient methods, and finite element methods Unsteady aerodynamics, and more
Unsteady Aerodynamics
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Author : Grigorios Dimitriadis
language : en
Publisher: John Wiley & Sons
Release Date : 2023-11-28
Unsteady Aerodynamics written by Grigorios Dimitriadis and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-11-28 with Technology & Engineering categories.
Unsteady Aerodynamics A comprehensive overview of unsteady aerodynamics and its applications The study of unsteady aerodynamics goes back a century and has only become more significant as aircraft become increasingly sophisticated, fly faster, and their structures are lighter and more flexible. Progress in the understanding of flow physics, computing power and techniques, and modelling technologies has led to corresponding progress in unsteady aerodynamics, with a wide range of methods currently used to predict the performance of engineering structures under unsteady conditions. Unsteady Aerodynamics offers a comprehensive and systematic overview of the application of potential and vortex methods to the subject. Beginning with an introduction to the fundamentals of unsteady flow, it then discusses the modelling of attached and separated, incompressible and compressible flows around two-dimensional and three-dimensional bodies. The result is an essential resource for design and simulation in aerospace engineering. Unsteady Aerodynamics readers will also find: MATLAB examples and exercises throughout, with codes and solutions on an accompanying website Detailed discussion of most classes of unsteady phenomena, including flapping flight, transonic flow, dynamic stall, flow around bluff bodies and more Validation of theoretical and numerical predictions using comparisons to experimental data from the literature Unsteady Aerodynamics is ideal for researchers, engineers, and advanced students in aerospace engineering.