Download or read book Static Aeroelastic Predictions for a Transonic Transport Model Using an Unstructured grid Flow Slover Coupled with a Structural Plate Technique written by Dennis O. Allison and published by . This book was released on 2003 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Static Aeroelastic Predictions for a Transonic Transport Model Using an Unstructured Grid Flow Solver Coupled With a Structural Plate Technique written by Dennis O. Allison and published by . This book was released on 2003 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Static Aeroelastic Predictions for a Transonic Transport Model Using an Unstructured Grid Flow Solver Coupled with a Structural Plate Technique written by National Aeronautics and Space Adm Nasa and published by . This book was released on 2018-09-21 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Philosophical Transactions of the Royal Society written by and published by . This book was released on 2007 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Transonic Flutter Prediction and Aeroelastic Tailoring for Next generation Transport Aircraft written by Max Maria Jacques Opgenoord and published by . This book was released on 2018 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: Novel commercial transport aircraft concepts feature large wing spans to increase their fuel efficiency; these wings are more flexible, leading to more potential aeroelastic problems. Furthermore, these aircraft fly in the transonic flow regime, where utter prediction is difficult. The goals for this thesis are to devise a method to reduce the computational burden of including transonic utter constraints in conceptual design tools, and to offer a potential solution for mitigating utter problems through the use of additive manufacturing techniques, specically focusing on a design methodology for lattice structures. To reduce the computational expense of considering transonic utter in conceptual aircraft design, a physics-based low-order method for transonic utter prediction is developed, which is based on small unsteady disturbances about a known steady flow solution. The states of the model are the circulation and doublet perturbations, and their evolution equation coefficients are calibrated using off-line unsteady two-dimensional flow simulations. The model is formulated for swept high-aspect ratio wings through strip theory and 3D corrections. The resulting low-order unsteady flow model is coupled to a typical-section structural model (for airfoils) or a beam model (for wings) to accurately predict utter of airfoils and wings. The method is fast enough to permit incorporation of transonic utter constraints in conceptual aircraft design calculations, as it only involves solving for the eigenvalues of small state-space systems. This model is used to describe the influence of transonic utter on next generation aircraft configurations, where it was found that transonic utter constraints can limit the eciency gains seen by better material technology. As a potential approach for mitigating utter, additively manufactured lattice structures are aeroelastically tailored to increase the flutter margin of wings. Adaptive meshing techniques are used to design the topology of the lattice to align with the load direction while adhering to manufacturing constraints, and the lattice is optimized to minimize the structural weight and to improve the flutter margin. The internal structure of a wing is aeroelastically tailored using this design strategy to increase the flutter margin, which only adds minimal weight to the structure due to the large design freedom the lattice structure offers.

Download or read book NASA SP written by and published by . This book was released on 1992 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Coupling Static Aeroelastic Predictions with an Unstructured grid Euler interacting Boundary Layer Method written by Peter Angelo Cavallo and published by . This book was released on 1995 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1998 with total page 980 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Three dimensional Time marching Aeroelastic Analyses Using an Unstructured grid Euler Method written by and published by . This book was released on 1992 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aeronautical Engineering written by and published by . This book was released on 1993 with total page 712 pages. Available in PDF, EPUB and Kindle. Book excerpt: A selection of annotated references to unclassified reports and journal articles that were introduced into the NASA scientific and technical information system and announced in Scientific and technical aerospace reports (STAR) and International aerospace abstracts (IAA)

Download or read book Aeronautical Engineering A Cumulative Index to a Continuing Bibliography supplement 287 written by and published by . This book was released on 1993 with total page 706 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Generalized Reduced Order Modeling of Aeroservoelastic Systems written by James Michael Gariffo and published by . This book was released on 2013 with total page 169 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transonic aeroelastic and aeroservoelastic (ASE) modeling presents a significant technical and computational challenge. Flow fields with a mixture of subsonic and supersonic flow, as well as moving shock waves, can only be captured through high-fidelity CFD analysis. With modern computing power, it is realtively straightforward to determine the flutter boundary for a single structural configuration at a single flight condition, but problems of larger scope remain quite costly. Some such problems include characterizing a vehicle's flutter boundary over its full flight envelope, optimizing its structural weight subject to aeroelastic constraints, and designing control laws for flutter suppression. For all of these applications, reduced-order models (ROMs) offer substantial computational savings. ROM techniques in general have existed for decades, and the methodology presented in this dissertation builds on successful previous techniques to create a powerful new scheme for modeling aeroelastic systems, and predicting and interpolating their transonic flutter boundaries. In this method, linear ASE state-space models are constructed from modal structural and actuator models coupled to state-space models of the linearized aerodynamic forces through feedback loops. Flutter predictions can be made from these models through simple eigenvalue analysis of their state-transition matrices for an appropriate set of dynamic pressures. Moreover, this analysis returns the frequency and damping trend of every aeroelastic branch. In contrast, determining the critical dynamic pressure by direct time-marching CFD requires a separate run for every dynamic pressure being analyzed simply to obtain the trend for the critical branch. The present ROM methodology also includes a new model interpolation technique that greatly enhances the benefits of these ROMs. This enables predictions of the dynamic behavior of the system for flight conditions where CFD analysis has not been explicitly performed, thus making it possible to characterize the overall flutter boundary with far fewer CFD runs. A major challenge of this research is that transonic flutter boundaries can involve multiple unstable modes of different types. Multiple ROM-based studies on the ONERA M6 wing are shown indicating that in addition to classic bending-torsion (BT) flutter modes. which become unstable above a threshold dynamic pressure after two natural modes become aerodynamically coupled, some natural modes are able to extract energy from the air and become unstable by themselves. These single-mode instabilities tend to be weaker than the BT instabilities, but have near-zero flutter boundaries (exactly zero in the absence of structural damping). Examples of hump modes, which behave like natural mode instabilities before stabilizing, are also shown, as are cases where multiple instabilities coexist at a single flight condition. The result of all these instabilities is a highly sensitive flutter boundary, where small changes in Mach number, structural stiffness, and structural damping can substantially alter not only the stability of individual aeroelastic branches, but also which branch is critical. Several studies are shown presenting how the flutter boundary varies with respect to all three of these parameters, as well as the number of structural modes used to construct the ROMs. Finally, an investigation of the effectiveness and limitations of the interpolation scheme is presented. It is found that in regions where the flutter boundary is relatively smooth, the interpolation method produces ROMs that predict the flutter characteristics of the corresponding directly computed models to a high degree of accuracy, even for relatively coarsely spaced data. On the other hand, in the transonic dip region, the interpolated ROMs show significant errors at points where the boundary changes rapidly; however, they still give a good qualitative estimate of where the largest jumps occur.

Download or read book Fast Prediction of Transonic Aeroelasticity Using Computational Fluid Dynamics written by Mark A. Woodgate and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The exploitation of computational fluid dynamics for non linear aeroelastic simulations is mainly based on time domain simulations of the Euler and Navier-Stokes equations coupled with structural models. Current industrial practice relies heavily on linear methods which can lead to conservative design and flight envelope restrictions. The significant aeroelastic effects caused by nonlinear aerodynamics include the transonic flutter dip and limit cycle oscillations. An intensive research effort is underway to account for aerodynamic nonlinearity at a practical computational cost. To achieve this a large reduction in the numbers of degrees of freedoms is required and leads to the construction of reduced order models which provide compared with CFD simulations an accurate description of the dynamical system at much lower cost. In this thesis we consider limit cycle oscillations as local bifurcations of equilibria which are associated with degenerate behaviour of a system of linearised aeroelastic equations. This extra information can be used to formulate a method for the augmented solve of the onset point of instability - the flutter point. This method contains all the fidelity of the original aeroelastic equations at much lower cost as the stability calculation has been reduced from multiple unsteady computations to a single steady state one. Once the flutter point has been found, the centre manifold theory is used to reduce the full order system to two degrees of freedom. The thesis describes three methods for finding stability boundaries, the calculation of a reduced order models for damping and for limit cycle oscillations predictions. Results are shown for aerofoils, and the AGARD, Goland, and a supercritical transport wing. It is shown that the methods presented allow results comparable to the full order system predictions to be obtained with CPU time reductions of between one and three orders of magnitude.

Download or read book Current Status of Computational Methods for Transonic Unsteady Aerodynamics and Aeroelastic Applications written by and published by . This book was released on 1992 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Predicting the Nonlinear Response of Aerospace Structures Using Aeroelastic NS Solutions on Deforming Meshes written by Rathinam Panneer Selvam and published by . This book was released on 2001 with total page 174 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the resurgent interest in flight vehicles such as the High-Speed Civil Transport (HSCT), the X-33 Advanced Technology Demonstrator, the Reusable Launch Vehicle (RLV), the Joint Strike Fighter (JSF) and the X-38 Spacecraft using a lifting-body concept that will Operate at supersonic/hypersonic Mach numbers, the need for panel flutter analysis has received broad acknowledgement. The linear and nonlinear analysis of the panel flutter has been studied extensive during the past two decades. However, most of the researches on this area are concentrated on the structural side, i.e., panel or plate. In these researches, the approximate theories, such as quasi-steady piston theory, full linearized (inviscid) potential flow theory, etc., are used to estimate the aerodynamic pressure. This kind of linear aerodynamics may not be adequate to predict the dynamic characteristics of the fluid and structure because the fluid flow is strongly nonlinear at the transonic and supersonic speeds. As we know, the high-fidelity equations, such as Euler or Navier-Stokes equations, can predict the flow characteristics more accurately. One of the important reasons that the high-fidelity equations have not been used to predict the aerodynamic loads is that the corresponding numerical simulation is very computationally expensive. With the fast development of the computer techniques, the full analysis of the nonlinear panel flutter coupled with the Euler or Navier-Stokes flow equations becomes possible.

Download or read book Research and Technology Highlights 1995 written by and published by . This book was released on 1996 with total page 154 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Aeroservoelasticity written by Ashish Tewari and published by Springer. This book was released on 2015-03-24 with total page 323 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph presents the state of the art in aeroservoelastic (ASE) modeling and analysis and develops a systematic theoretical and computational framework for use by researchers and practicing engineers. It is the first book to focus on the mathematical modeling of structural dynamics, unsteady aerodynamics, and control systems to evolve a generic procedure to be applied for ASE synthesis. Existing robust, nonlinear, and adaptive control methodology is applied and extended to some interesting ASE problems, such as transonic flutter and buffet, post-stall buffet and maneuvers, and flapping flexible wing. The author derives a general aeroservoelastic plant via the finite-element structural dynamic model, unsteady aerodynamic models for various regimes in the frequency domain, and the associated state-space model by rational function approximations. For more advanced models, the full-potential, Euler, and Navier-Stokes methods for treating transonic and separated flows are also briefly addressed. Essential ASE controller design and analysis techniques are introduced to the reader, and an introduction to robust control-law design methods of LQG/LTR and H2/H∞ synthesis is followed by a brief coverage of nonlinear control techniques of describing functions and Lyapunov functions. Practical and realistic aeroservoelastic application examples derived from actual experiments are included throughout. Aeroservoelasiticity fills an important gap in the aerospace engineering literature and will be a valuable guide for graduate students and advanced researchers in aerospace engineering, as well as professional engineers, technicians, and test pilots in the aircraft industry and laboratories.