Dissertations / Theses on the topic 'Aeroelasticity'
To see the other types of publications on this topic, follow the link: Aeroelasticity.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Aeroelasticity.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Swift, Adam. "Simulation of aircraft aeroelasticity." Thesis, University of Liverpool, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.569519.
Full textAbstract:
Aeroelastic phenomena such as flutter can have a detrimental effect on aircraft performance and can lead to severe damage or destruction. Buffet leads to a re- duced fatigue life and therefore higher operating costs and a limited performance envelope. As such the simulation of these aeroelastic phenomena is of utmost importance. Computational aeroelasticity couples computational fluid dynamics and computational structural dynamics solvers through the use of a transforma- tion method. There have been interesting developments over the years towards more efficient methods for predicting the flutter boundaries based upon the sta- bility of the system of equations. This thesis investigates the influence of transformation methods on the flutter boundary predition and considers the simulation of shock-induced buffet of a transport wing. This involves testing a number of transformation methods for their effect on flutter boundaries for two test cases and verifying the flow solver for shock-induced buffet over an aerofoil. This will be followed by static aeroelastic calculations of an aeroelastic wing. It is shown that the transformation methods have a significant effect on the predicted flutter boundary. Multiple transformation methods should be used to build confidence in the results obtained, and extrapolation should be avoided. CFD predictions are verified for buffet calculations and the mechanism behind shock-oscillation of the BGK No. 1 aerofoil is investigated. The use of steady calculations to assess if a case may be unsteady is considered. Finally the static aeroelastic response of the ARW-2 wing is calculated and compared against ex- perimental results.
2
Souza, Carlos Eduardo de. "Nonlinear aeroelasticity of composite flat plates." Instituto Tecnológico de Aeronáutica, 2012. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2243.
Full textAbstract:
This work presents a study on aeroelastic analyses of composite laminated flat plates subject to large displacements through the coupling of a nonlinear corotational shell finite element (FE) with an unsteady vortex-lattice method (UVLM) formulation. A FE implemented for the analysis of flat plates has been extended to model laminated composites with different lamina orientations. An UVLM formulation that is capable of coupling with this large displacement structural model is implemented. An explicit partitioned method is evaluated for the coupling of both models, using spline functions to interpolate information from the structural operator to the aerodynamic one, inside a Generalized-? time-marching solution. The resulting aeroelastic formulation provides a framework able of performing time marching simulation of structures made of composite material allowing the characterization of their nonlinear behavior and of the limit-cycle oscillation response. Laminated flat plates designed for high flexibility and low flutter speed onset are used as investigation models. To support the numerical studies, test specimens made of carbon fiber were used in experimental modal analysis and wind tunnel aeroelastic tests. Effects of nonlinearities are easily observed in the numerical results, which are promising for expansion of the work and application to the analysis of more refined and complex composite flexible wings.
3
Bueno, Douglas Domingues. "A contribution to aeroelasticity using lyapunov's theory." Instituto Tecnológico de Aeronáutica, 2014. http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=3035.
Full textAbstract:
The main idea of this work is to apply the general theory of stability introduced by Lyapunov and to use linear matrix inequalities (LMIs) to study different issues in aeroservoelasticity. Many approaches have been developed on the control theory field involving LMIs, however, there is a limited number of works in the literature focused on aeroelasticity. That preliminary motivation allowed the development of different approaches on this topic. Three benchmark systems were used to evaluate and demonstrate these approaches. The first one is the three degree of freedom airfoil section and the second one is the AGARD 445.6 wing. The third benchmark system is the two degree of freedom pitch and plunge apparatus. The aerodynamic forces were computed using the Theodorsen';s theory and the Doublet Lattice method. Four different issues involving stability and control are discussed. The first one is the inclusion of structural uncertainties on the stability analysis. The second topic introduces the concept of continuous analysis and allows the study of stability of time-variant aeroelastic systems. The third issue comprises the design of controllers to suppress limit cycle oscillations in aeroelastic systems including discrete nonlinearities based on the Fuzzy Takagi-Sugeno modeling and, finally, the last topic proposes the use of Grammian matrices to determine the linear stability specially when a large number of cases of analysis are considered in the flight envelope. The introduced ideas are very promising for aeroservoelastic analysis using LMIs.
4
Natarajan, Anand. "Aeroelasticity of Morphing Wings Using Neural Networks." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/28267.
Full textAbstract:
In this dissertation, neural networks are designed to effectively model static non-linear aeroelastic problems in adaptive structures and linear dynamic aeroelastic systems with time varying stiffness. The use of adaptive materials in aircraft wings allows for the change of the contour or the configuration of a wing (morphing) in flight. The use of smart materials, to accomplish these deformations, can imply that the stiffness of the wing with a morphing contour changes as the contour changes. For a rapidly oscillating body in a fluid field, continuously adapting structural parameters may render the wing to behave as a time variant system. Even the internal spars/ribs of the aircraft wing which define the wing stiffness can be made adaptive, that is, their stiffness can be made to vary with time. The immediate effect on the structural dynamics of the wing, is that, the wing motion is governed by a differential equation with time varying coefficients. The study of this concept of a time varying torsional stiffness, made possible by the use of active materials and adaptive spars, in the dynamic aeroelastic behavior of an adaptable airfoil is performed here.
A time marching technique is developed for solving linear structural dynamic problems with time-varying parameters. This time-marching technique borrows from the concept of Time-Finite Elements in the sense that for each time interval considered in the time-marching, an analytical solution is obtained. The analytical solution for each time interval is in the form of a matrix exponential and hence this technique is termed as Matrix Exponential time marching. Using this time marching technique, Artificial Neural Networks can be trained to represent the dynamic behavior of any linearly time varying system. In order to extend this methodology to dynamic aeroelasticity, it is also necessary to model the unsteady aerodynamic loads over an airfoil. Accordingly, an unsteady aerodynamic panel method is developed using a distributed set of doublet panels over the surface of the airfoil and along its wake. When the aerodynamic loads predicted by this panel method are made available to the Matrix Exponential time marching scheme for every time interval, a dynamic aeroelastic solver for a time varying aeroelastic system is obtained. This solver is now used to train an array of neural networks to represent the response of this two dimensional aeroelastic system with a time varying torsional stiffness. These neural networks are developed into a control system for flutter suppression.
Another type of aeroelastic problem of an adaptive structure that is investigated here is the shape control of an adaptive bump situated on the leading edge of an airfoil. Such a bump is useful in achieving flow separation control for lateral directional maneuverability of the aircraft. Since actuators are being used to create this bump on the wing surface, the energy required to do so needs to be minimized. The adverse pressure drag as a result of this bump needs to be controlled so that the loss in lift over the wing is made minimal. The design of such a "spoiler bump" on the surface of the airfoil is an optimization problem of maximizing pressure drag due to flow separation while minimizing the loss in lift and energy required to deform the bump. One neural network is trained using the CFD code FLUENT to represent the aerodynamic loading over the bump. A second neural network is trained for calculating the actuator loads, bump displacement and lift, drag forces over the airfoil using the finite element solver, ANSYS and the previously trained neural network. This non-linear aeroelastic model of the deforming bump on an airfoil surface using neural networks can serve as a fore-runner for other non-linear aeroelastic problems.
This work enhances the traditional aeroelastic modeling by introducing time varying parameters in the differential equations of motion. It investigates the calculation of non-conservative aerodynamic loads on morphing contours and the resulting structural deformation for non-linear aeroelastic problems through the use of neural networks. Geometric modeling of morphing contours is also addressed.Ph. D.
5
Liu, Shaobin. "Continuum Sensitivity Method for Nonlinear Dynamic Aeroelasticity." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23282.
Full textAbstract:
In this dissertation, a continuum sensitivity method is developed for efficient and accurate computation of design derivatives for nonlinear aeroelastic structures subject to transientaerodynamic loads. The continuum sensitivity equations (CSE) are a set of linear partial
differential equations (PDEs) obtained by differentiating the original governing equations of
the physical system. The linear CSEs may be solved by using the same numerical method
used for the original analysis problem. The material (total) derivative, the local (partial)
derivative, and their relationship is introduced for shape sensitivity analysis. The CSEs are
often posed in terms of local derivatives (local form) for fluid applications and in terms of total
derivatives (total form) for structural applications. The local form CSE avoids computing
mesh sensitivity throughout the domain, as required by discrete analytic sensitivity methods.
The application of local form CSEs to built-up structures is investigated. The difficulty
of implementing local form CSEs for built-up structures due to the discontinuity of local
sensitivity variables is pointed out and a special treatment is introduced. The application
of the local form and the total form CSE methods to aeroelastic problems are compared.
Their advantages and disadvantages are discussed, based on their derivations, efficiency,
and accuracy. Under certain conditions, the total form continuum method is shown to be
equivalent to the analytic discrete method, after discretization, for systems governed by a
general second-order PDE. The advantage of the continuum sensitivity method is that less
information of the source code of the analysis solver is required. Verification examples are
solved for shape sensitivity of elastic, fluid and aeroelastic problems.
Ph. D.
6
Kamakoti, Ramji. "Computational aeroelasticity using a pressure-based solver." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0005683.
Full text
7
Seywald, Klaus. "Wingbox Mass Prediction considering Quasi-Static Nonlinear Aeroelasticity." Thesis, KTH, Flygdynamik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-59014.
Full textAbstract:
Nonplanar wing configurations promise a significant improvement of aerodynamic efficiency and are therefore currently investigated for future aircraft configurations. A reliable mass prediction for a new wing configuration is of great importance in preliminary aircraft design in order to enable a holistic assessment of potential benefits and drawbacks. In this thesis a generic numerical modeling approach for arbitrary unconventional wing configurations is developed and a simulation tool for their evaluation and mass prediction is implemented. The wingbox is modeled with a nonlinear finite element beam which is coupled to different low-fidelity aerodynamic methods obtaining a quasi-static aeroelastic model that considers the redistribution of aerodynamic forces due to deformation. For the preliminary design of the wingbox various critical loading conditions according to the Federal Aviation Regulations are taken into account. The simulation tool is validated for a range of existing aircraft types. Additionally, two unconventional configurations, the C-wing and the box-wing, are analyzed. The outlook provides suggestions for extensions and further development of the simulation tool as well as possible model refinements.
8
Feng, Zhengkun. "A nonlinear computational aeroelasticity model for aircraft wings." Mémoire, Montréal : École de technologie supérieure, 2005. http://wwwlib.umi.com/cr/etsmtl/fullcit?pNR06026.
Full textAbstract:
Thèse (Ph.D.)-- École de technologie supérieure, Montréal, 2005."Thesis presented to École de technologie supérieure in fulfillment of the thesis requirement for the degree of doctor of philosophy". Bibliogr.: f. [160]-168. Également disponible en version électronique.
9
Banerjee, J. R. "Advances in structural dynamics, aeroelasticity and material science." Thesis, City University London, 2015. http://openaccess.city.ac.uk/14901/.
Full textAbstract:
This submission for the degree of Doctor of Science includes all the publications by the author and a description of his research, covering the period 1969-2015. The main contributions to knowledge made by the author concern his new approaches to structural dynamics, aeroelasticity, material science and related problems. In particular, the major activities of his research relate to the (i) free vibration and buckling analysis of structures, (ii) dynamic stiffness formulation, (iii) response of metallic and composite structures to deterministic and random loads, (iv) aeroelasticity of metallic and composite aircraft, (v) a unified approach to flutter, dynamic stability and response of aircraft, (vi) aeroelastic optimisation and active control, (vii) application of symbolic computation in structural engineering research, (viii) development of software packages for computer aided structural analysis and design and (ix) thermal properties of polymer nanocomposites and hot ductility of steel. The free vibration analysis of structures is a research topic which has been an age old companion of the author ever since he was working for his Master’s degree in Mechanical Engineering in the early 1970s, when he chose a crankshaft vibration problem of the Indian Railways as the research topic for his Master’s thesis. With increasing maturity and experience, he provided solutions to vibration and buckling problems ranging from a simple single structural element to a high capacity transport airliner capable of carrying more than 500 passengers and a large space platform with a plan dimension of more than 30 metres. To provide these solutions, he resorted to an elegant, accurate, but efficient method, called the dynamic stiffness method, which uses the so-called dynamic stiffness matrix of a structural element as the basic building block in the analysis. The author has developed dynamic stiffness matrices of a large number of structural elements including beams, plates and shells with varying degrees of complexity, particularly including those made of composite materials. Recently he published the dynamic stiffness matrices of isotropic and anisotropic rectangular plates for the most general case when the plate boundaries are free at all edges. Computation of natural frequencies of isotropic and anisotropic plates and their assemblies for any boundary conditions in an exact sense has now become possible for the first time as a result of this development. This ground-breaking research has opened up the possibility of developing general purpose computer programs using the dynamic stiffness method for computer-aided structural analysis and design. Such computer programs will be vastly superior to existing computer programs based on the finite element method, both in terms to accuracy and computational efficiency. This is in line with the author’s earlier research on free vibration and buckling analysis of skeletal structures which led to the development of the computer program BUNVIS (Buckling or Natural Vibration of Space Frames) and BUNVIS-RG (Buckling or Natural Vibration of Space Frames with Repetitive Geometry) which received widespread attention. Numerous research papers emerged using BUNVIS and BUNVIS-RG as research tools. The author’s main contributions in the Aeronautical Engineering field are, however, related to the solutions of problems in aeroelasticity, initially for metallic aircraft and in later years for composite aircraft. He investigated the aeroelastic problems of tailless aircraft for the first time in his doctoral studies about 40 years ago. In this research, a unified method combining two major disciplines of aircraft design, namely that of stability and control, and that of flutter and response, was developed to study the interaction between the rigid body motions of an aircraft and its elastic modes of distortion. The computer program CALFUN (CALculation of Flutter speed Using Normal modes) was developed by the author for metallic aircraft and later extended to cover composite aircraft. The associated theories for composite aircraft were developed and the allied problems of dynamic response to both deterministic and random loads were solved. With the advent of advanced composite materials, the author’s research turned to aeroelasticity of composite aircraft and then to optimization studies. New, novel and accurate methods were developed and significant inroads were made. The author broke new ground by applying symbolic computation as an aid to the solution of his research problems. The computational efficiency of this new approach became evident as a by-product of his research. The development of software based on his theories has paved the way for industrial applications. His research works on dynamic stiffness modelling of composite structures using layer-wise and higher order shear deformation theory are significant developments in composites engineering. Such pioneering developments were necessitated by the fact that existing methodologies using classical lamination theory are not sufficiently accurate, particularly when the structural components made from composite materials are thick, e.g. the fuselage of a transport airliner. Given the close relationship between structural engineering and material science, the author’s research has broadened into polymers and nano-composites, functionally graded materials and hot ductility of steel. His research activities are continuing and expanding with further diversification of his interests.
10
Eller, David. "On an Efficient Method fo Time-Domain Computational Aeroelasticity." Doctoral thesis, KTH, Farkost och flyg, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-584.
Full textAbstract:
The present thesis summarizes work on developing a method for unsteady aerodynamic analysis primarily for aeroelastic simulations. In contrast to widely used prediction tools based on frequency-domain representations, the current approach aims to provide a time-domain simulation capability which can be readily integrated with possibly nonlinear structural and control system models. Further, due to the potential flow model underlying the computational method, and the solution algorithm based on an efficient boundary element formulation, the computational effort for the solution is moderate, allowing time-dependent simulations of complex configurations. The computational method is applied to simulate a number of wind-tunnel experiments involving highly flexible models. Two of the experiments are utilized to verify the method and to ascertain the validity of the unsteady flow model. In the third study, simulations are used for the numerical optimization of a configuration with multiple control surfaces. Here, the flexibility of the model is exploited in order to achieve a reduction of induced drag. Comparison with experimental results shows that the numerical method attains adequate accuracy within the inherent limits of the potential flow model. Finally, rather extensive aeroelastic simulations are performed for the ASK 21 sailplane. Time-domain simulations of a pull-up maneuver and comparisons with flight test data demonstrate that, considering modeling and computational effort, excellent agreement is obtained. Furthermore, a flutter analysis is performed for the same aircraft using identified frequency-domain loads. Results are found to deviate only slightly from critical speed and frequency obtained using an industry-standard aeroelastic analysis code. Nevertheless, erratic results for control surface hinge moments indicate that the accuracy of the present method would benefit from improved control surface modeling and coupled boundary layer analysis.QC 20100531
11
Eller, David. "On an efficient method for time-domain computational aeroelasticity /." Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-584.
Full text
12
Woodgate, Mark A. "Fast prediction of transonic aeroelasticity using computational fluid dynamics." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/923/.
Full textAbstract:
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.
13
Cheng, Tao 1975. "Structural dynamics modeling of helicopter blades for computational aeroelasticity." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/37563.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2002.Page 180 blank.
Includes bibliographical references (p. 177-179).
This thesis deals with structural dynamics modeling and simulation in time domain of helicopter blades for computational aeroelasticity. A structural model and an aeroelastic model are provided and a computer program has been developed and tested in this research. In the structural model, second-order backward Euler method is used to discretize the nonlinear intrinsic formulation for the dynamics of rotating blades in time. Newton method is used to solve the resulting nonlinear algebraic equations. The solution describes the displacement field, stress and strain field at each time step of twist composite hingeless or articulated rotor blades under the action of arbitrary external loads. Results are validated by experimental data and other numerical simulation work for various conditions. Then the aerodynamic model implemented via the GENUVP code is integrated with the structural model to form an aeroelastic simulation. The aeroelastic analysis is realized in time domain by exchanging information with two interfaces and performing consecutive aerodynamic and structural time steps. In the aeroelastic analysis, the steady state of a fixed wing at different flight speeds have been obtained and results are consistent with other methods. The time response of the active twist rotor (ATR) prototype blade in hover has also been examined. The twist response of ATR blade due to applied piezoelectric actuation is obtained and the result compared with published results. A good qualitative agreement between the present aeroelastic solution and reference results was obtained. However, quantitative discrepancies were encountered that strongly suggest that further improvements on the coupling between the two codes are needed. For all the aeroelastic test cases using the GENUVP code, no sub-iterations within a time step was used. A study considering a simple quasi-steady aerodynamics indicated that a sub-iteration in each time step may be critical to the accuracy of the final aeroelastic result. Recommendations for further work is provided at the end.
by Tao Cheng.
S.M.
14
Newsom, Jerry Russell. "Designing Active Control Laws in a Computational Aeroelasticity Environment." Diss., Virginia Tech, 2002. http://hdl.handle.net/10919/26495.
Full textAbstract:
The purpose of this dissertation is to develop a methodology for designing active control laws in a computational aeroelasticity environment. The methodology involves employing a systems identification technique to develop an explicit state-space model for control law design from the output of a computational aeroelasticity code. The particular computational aeroelasticity code employed in this dissertation solves the transonic small disturbance equation using a time-accurate, finite-difference scheme. Linear structural dynamics equations are integrated simultaneously with the computational fluid dynamics equations to determine the time responses of the structural outputs. These structural outputs are employed as the input to a modern systems identification technique that determines the Markov parameters of an â equivalent linear systemâ . The eigensystem realization algorithm is then employed to develop an explicit state-space model of the equivalent linear system. Although there are many control law design techniques available, the standard Linear Quadratic Guassian technique is employed in this dissertation. The computational aeroelasticity code is modified to accept control laws and perform closed-loop simulations. Flutter control of a rectangular wing model is chosen to demonstrate the methodology. Various cases are used to illustrate the usefulness of the methodology as the nonlinearity of the computational fluid dynamics system is increased through increased angle-of-attack changes.Ph. D.
15
Dribusch, Christoph. "Multi-Fidelity Construction of Explicit Boundaries: Application to Aeroelasticity." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/293482.
Full textAbstract:
Wings, control surfaces and rotor blades subject to aerodynamic forces may exhibit aeroelastic instabilities such as flutter, divergence and limit cycle oscillations which generally reduce their life and functionality. This possibility of instability must be taken into account during the design process and numerical simulation models may be used to predict aeroelastic stability. Aeroelastic stability is a design requirement that encompasses several difficulties also found in other areas of design. For instance, the large computational time associated with stability analysis is also found in computational fluid dynamics (CFD) models. It is a major hurdle in numerical optimization and reliability analysis, which generally require large numbers of call to the simulation code. Similarly, the presence of bifurcations and discontinuities is also encountered in structural impact analysis based on nonlinear dynamic simulations and renders traditional approximation techniques such as Kriging ineffective. Finally, for a given component or system, aeroelastic instability is only one of multiple failure modes which must be accounted for during design and reliability studies. To address the above challenges, this dissertation proposes a novel algorithm to predict, over a range of parameters, the qualitative outcomes (pass/fail) of simulations based on relatively few, classified (pass/fail) simulation results. This is different from traditional approximation techniques that seek to predict simulation outcomes quantitatively, for example by fitting a response surface. The predictions of the proposed algorithm are based on the theory of support vector machines (SVM), a machine learning method originated in the field of pattern recognition. This process yields an analytical function that explicitly defines the boundary between feasible and infeasible regions of the parameter space and has the ability to reproduce nonlinear, disjoint boundaries in n dimensions. Since training the SVM only requires classification of training samples as feasible or infeasible, the presence of discontinuities in the simulation results does not affect the proposed algorithm. For the same reason, multiple failure modes such as aeroelastic stability, maximum stress or geometric constraints, may be represented by a single SVM predictor. Often, multiple models are available to simulate a given design at different levels of fidelity and small improvements in accuracy may increase simulation cost by an order of magnitude. In many cases, a lower-fidelity model will classify a case correctly as feasible or infeasible. Therefore a multi-fidelity algorithm is proposed that takes advantage of lower-fidelity models when appropriate to minimize the overall computational burden of training the SVM. To this end, the algorithm combines the concepts of adaptive sampling and multi-fidelity analysis to iteratively select not only the training samples, but also the appropriate level of fidelity for evaluation. The proposed algorithm, referred to as multi-fidelity explicit design space decomposition (MF-EDSD), is demonstrated on various models of aeroelastic stability to either build the stability boundary and/or to perform design optimization. The aeroelastic models range from linear and nonlinear analytical models to commercial software (ZAERO) and represent divergence, flutter, and limit cycle oscillation instabilities. Additional analytical test problems have the advantage that the accuracy of the SVM predictor and the convergence to optimal designs are more easily verified. On the other hand the more sophisticated models demonstrate the applicability to real aerospace applications where the solutions are not known a priori. In conclusion, the presented MF-EDSD algorithm is well suited for approximating stability boundaries associated with aeroelastic instabilities in high-dimensional parameter spaces. The adaptive selection of training samples and use of multi-fidelity models leads to large reductions of simulation cost without sacrificing accuracy. The SVM representation of the boundary of the feasible design space provides a single differentiable constraint function with negligible evaluation cost, ideal for numerical optimization and reliability quantification.
16
Gu, Xiao Han Phrain. "Impinging Leading Edge Vortex Induced OsauATiON (ILEVIO) in Bridge Aeroelasticity." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.523660.
Full text
17
Khodaparast, Hamed Haddad. "Stochastic finite element model updating and its application in aeroelasticity." Thesis, University of Liverpool, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548785.
Full text
18
Saiz, Gabriel. "Turbomachinery Aeroelasticity Using a Time-Linearised Multi Blade-row Approach." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486578.
Full textAbstract:
In turbomachinery, the continuous drive towards low weight and improved efficiency has led to the design of slender and lighter blades, resulting in higher stress levels and aeroelasticity interactions on blades. Consequently, fast and accurate predictions of turbomachinery aeroelasticity phenomena are essential to modern aero-engine design. Current prediction methods can be divided into three main categories: classical, nonlinear time-accurate,and harmonic. Classical methods work with simplified geometries and simplified flow conditions, and are therefore not reliable for design. Nonlinear time-accurate methods are usually accurate, but they demand too much computational effort to be used for design in the foreseeable future. Harmonic methods currently meet design efficiency requirements, but they can still lack accuracy in real turbomachinery applications. Several research works suggest that one of the reasons for this is that most current methods ignore potentially important multi blade-row effects. . In this thesis, a harmonic Iinearised solver for the computation of multi-stage unsteady turbomachinery flows was developed. Blade-row interactions were represented using the theory of spinning modes. The new method uses either the 3-D Euler or Navier-Stokes equations and is well suited to the computation of flutter and forced response. Efficient solutions were obtained thanks to the use of state-of-the-art acceleration techniques, such as local Jacobi. preconditioner, multigrid, and GMRES. The method uses modern 3-D nonreflective boundary conditions, which use a wave-splitting method to minimise numerical reflections at the far-field boundaries. It also uses a novel inter-row boundary condition, based on the same wave-splitting method, to transfer waves between blade-rows. The new method was first tested for stator-rotor interaction and flutter on both simplified. geometries and flow conditions; results showed excellent agreement with the reference solutions. The method was then validated on industrial turbine configurations. Results were compared with nonlinear time-accurate unsteady solutions and experimental data and showed good agreement. It was demonstrated that multi-blade-row effects on the----. aerodynamic damping and the modal force of the vibrating blade-row are significant. The new method is also very efficient; large gains in computing time were obtained compared to ) fully nonlinear time-accurate methods.
19
Di, Donfrancesco Fabrizio. "Reduced Order Models for the Navier-Stokes equations for aeroelasticity." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS603.
Full textAbstract:
Le coût d’une simulation numérique aéroélastique peut devenir trop onéreuse lorsque une analyse paramétrique à haut fidélité est requise. Dans ce contexte, des Modèles d'Ordre Réduit (MOR) ont été développés en vue de réduire le coût de calcul des simulations numériques en préservant un haut niveau de précision. Ce travail de thèse porte sur la construction d'un MOR pour les équations de Navier-Stokes en tenant compte d'un maillage déformable dans le cas d'une application aéroélastique. Une base modale pour l'écoulement est obtenue via la Décomposition Orthogonale aux valeurs propres et une projection Galerkin est utilisée pour réduire le système d'équations de la mécanique des fluides. Pour pouvoir prendre en compte les non-linéarités des équation de Navier-Stokes une méthode de projection masquée est mise en œuvre et évaluée pour différent cas test avec maillage fixe. Le MOR est ensuite adapté pour prendre en compte des maillages déformables. Finalement, une méthode réduite spectrale en temps (ROTSM) a été formulée afin de répondre aux problèmes de stabilité qui concernent le MORs avec projection dans le domaine de la mécanique des fluides. Une évaluation du MOR obtenu est ensuite menée sur des études paramétriques pour des applications aéroélastiquesThe numerical prediction of aeroelastic systems responses becomes unaffordable when parametric analyses with high-fidelity CFD are required. Reduced order modeling (ROM) methods have therefore been developed in view of reducing the costs of the numerical simulations while preserving a high level of accuracy. The present thesis focuses on the family of projection based methods for the compressible Navier-Stokes equations involving deforming meshes in the case of aeroelastic applications. A vector basis obtained by Proper Orthogonal Decomposition (POD) combined to a Galerkin projection of the system equations is used in order to build a ROM for fluid mechanics. Masked projection approaches are therefore implemented and assessed for different test cases with fixed boundaries in order to provide a fully nonlinear formulation for the projection-based ROMs. Then, the ROM is adapted in the case of deforming boundaries and aeroelastic applications in a parametric context. Finally, a Reduced Order Time Spectral Method (ROTSM) is formulated in order to address the stability issues which involve the projection-based ROMs for fluid mechanics applications
20
Singh, Beerinder. "Dynamics and aeroelasticity of hover-capable flapping wings experiments and analysis /." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/6663.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
21
Van, Zyl Louwrens Hermias. "Advanced linear methods for T-tail aeroelasticity / Louwrens Hermias van Zyl." Thesis, North-West University, 2011. http://hdl.handle.net/10394/8492.
Full textAbstract:
Flutter is one of the primary aeroelastic phenomena that must be considered in aircraft design.
Flutter is a self-sustaining structural vibration in which energy is extracted from the air flow and
transferred to the structure. The amplitude of the vibration grows exponentially until structural
failure occurs. Flutter stability requirements often influence the design of an aircraft, making
accurate flutter prediction capabilities an essential part of the design process. Advances in
computational fluid dynamics and computational power make it possible to solve the fluid flow and
structural dynamics simultaneously, providing highly accurate solutions especially in the transonic
flow regime. This procedure is, however, too time-consuming to be used in the design optimisation
process. As a result panel codes, e.g., the doublet lattice method, and modal-based structural
analysis methods are still being used extensively and continually improved.
One application that is lagging in terms of accuracy and simplicity (from the user’s perspective)
is the flutter analysis of T-tails. The flutter analysis of a T-tail usually involves the calculation of
additional aerodynamic loads, apart from the loads calculated by the standard unsteady
aerodynamic codes for conventional empennages. The popular implementations of the doublet
lattice method do not calculate loads due to the in-plane motion (i.e., lateral or longitudinal motion)
of the horizontal stabiliser or the in-plane loads on the stabiliser. In addition, these loads are
dependent on the steady-state load distribution on the stabiliser, which is ignored in the doublet
lattice method.
The objective of the study was to extend the doublet lattice method to calculate the additional
aerodynamic loads that are crucial for T-tail flutter analysis along with the customary unsteady air
loads for conventional configurations. This was achieved by employing the Kutta-Joukowski
theorem in the calculation of unsteady air loads on lifting surface panels. Calculating the additional
unsteady air loads for T-tails within the doublet lattice method significantly reduces the human
effort required for T-tail flutter analysis as well as the opportunities for introducing errors into the
analysis.
During the course of the study it became apparent that it was necessary to consider the quadratic
mode shape components in addition to the linear mode shape components. Otherwise the unsteady
loads due to the rotation (“tilting”) of the steady-state load on the stabiliser, one of the additional
aerodynamic loads that are crucial for T-tail flutter analysis, would give rise to spurious generalised
forces. In order to reduce the additional burden of determining the quadratic mode shape components, methods for calculating quadratic mode shape components using linear finite element
analysis or estimating them from the linear mode shape components were developed.
Wind tunnel tests were performed to validate the proposed computational method. A T-tail
flutter model which incorporated a mechanism for changing the incidence angle of the horizontal
stabiliser, and consequently the steady-state load distribution on the horizontal stabiliser, was used.
The flutter speed of this model as a function of the horizontal stabiliser incidence was determined
experimentally and compared to predictions. Satisfactory correlation was found between predicted
and experimentally determined flutter speeds.Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2012
22
Kwon, Oh Joon. "A technique for the prediction of aerodynamics and aeroelasticity of rotor blades." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/12159.
Full text
23
Rohrschneider, Reuben R. "Variable-Fidelity Hypersonic Aeroelastic Analysis of Thin-Film Ballutes for Aerocapture." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14590.
Full textAbstract:
Ballute hypersonic aerodynamic decelerators have been considered for aerocapture since the early 1980's. Recent technology advances in fabric and polymer materials as well as analysis capabilities lend credibility to the potential of ballute aerocapture. The concept of the thin-film ballute for aerocapture shows the potential for large mass savings over propulsive orbit insertion or rigid aeroshell aerocapture. Several technology hurdles have been identified, including the effects of coupled fluid structure interaction on ballute performance and survivability. To date, no aeroelastic solutions of thin-film ballutes in an environment relevant to aerocapture have been published.
In this investigation, an aeroelastic solution methodology is presented along with the analysis codes selected for each discipline. Variable-fidelity aerodynamic tools are used due to the long run times for computational fluid dynamics or direct simulation Monte Carlo analyses. The improved serial staggered method is used to couple the disciplinary analyses in a time-accurate manner, and direct node-matching is used for data transfer. In addition, an engineering approximation has been developed as an addition to modified Newtonian analysis to include the first-order effects of damping due to the fluid, providing a rapid dynamic aeroelastic analysis suitable for conceptual design.
Static aeroelastic solutions of a clamped ballute on a Titan aerocapture trajectory are presented using non-linear analysis in a representative environment on a flexible structure. Grid convergence is demonstrated for both structural and aerodynamic models used in this analysis. Static deformed shape, drag and stress level are predicted at multiple points along the representative Titan aerocapture trajectory. Results are presented for verification and validation cases of the structural dynamics and simplified aerodynamics tools. Solutions match experiment and other validated codes well.
Contributions of this research include the development of a tool for aeroelastic analysis of thin-film ballutes which is used to compute the first high-fidelity aeroelastic solutions of thin-film ballutes using inviscid perfect-gas aerodynamics. Additionally, an aerodynamics tool that implements an engineering estimate of hypersonic aerodynamics with a moving boundary condition is developed and used to determine the flutter point of a thin-film ballute on a Titan aerocapture trajectory.
24
Unger, Eric Robert. "Integrated aerodynamic-structural wing design optimization." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-09042008-063104/.
Full text
25
Marshall, John Graham. "Prediction of turbomachinery aeroelasticity effects using a 3D non-linear integrated method." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244501.
Full text
26
Wu, Daniel. "The Effect of Blade Aeroelasticity and Turbine Parameters on Wind Turbine Noise." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78714.
Full textAbstract:
In recent years, the demand for wind energy has dramatically increased as well as the number and size of commercial wind turbines. These large turbines are loud and can cause annoyance to nearby communities. Therefore, the prediction of large wind turbine noise over long distances is critical. The wind turbine noise prediction is a very complex problem since it has to account for atmospheric conditions (wind and temperature), ground absorption, un-even terrain, turbine wake, and blade deformation. In these large turbines, the blade deflection is significant and it can potentially influence the noise emissions. However, the effects of blade flexibility on turbine noise predictions have not been addressed yet, i.e. all previous research efforts have assumed rigid blades. To address this shortcoming, the present work merges a wind turbine aeroelastic code, FAST (Fatigue, Aerodynamics, Structures, and Turbulence) to a wind turbine noise code, WTNoise, to compute turbine noise accounting for blade aeroelasticity. Using the newly developed simulation tool, the effects flexible blades on wind turbine noise are investigated, as well as the effects of turbine parameters, e.g. wind conditions, rotor size, tilt, yaw, and pre-cone angles. The acoustic results are shown as long term average overall sound power level distribution over the rotor, ground noise map over a large flat terrain, and noise spectrum at selected locations downwind. To this end, two large wind turbines are modeled. The first one is the NREL 5MW turbine that has a rotor diameter of 126 m. The second wind turbine, the Sandia 13.2MW, has a rotor diameter of 206 m. The results show that the wind condition has strong effects on the noise propagation over long distances, primarily in the upwind direction. In general, the turbine parameters have no significant effects on the average noise level. However, the turbine yaw impacts significantly the turbine noise footprint by affecting the noise propagation paths. The rotor size is also a dominating factor in the turbine noise level. Finally, the blade aeroelasticity has minor effects on the turbine noise. In summary, a comprehensive tool for wind turbine noise prediction including blade aeroelasticity was developed and it was used to address its impact on modern large turbine noise emissions.Master of Science
27
Navrátil, Jan. "New Approaches in Numerical Aeroelasticity Applied in Aerodynamic Optimization of Elastic Wing." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-263386.
Full textAbstract:
Aeroelasticita je nezbytná vědní disciplína zahrnuta do návrhu letounů. Zaměřuje se na předpovídání jevů, které vznikají vlivem interakce aerodynamických, elastických a setrvačných sil. Tyto jevy často vedou ke katastrofickým následkům, proto musí být prokázáno, že nevzniknou v rozsahu rychlostí ohraničujících letovou obálku. Aplikace moderních materiálů při konstrukci draku, spolu se snahou navrhnout aerodynamicky efektivní tvar křídel, vede ke zvyšování poddajnosti letounů. To má za následek změnu aerodynamických vlastností a také k výraznějšímu vliv na aeroelastické jevy, které mohou být vyvolány snadněji vlivem pohybů tuhého tělesa než v případě tužších konstrukcí. Aeroelastické jevy mohou vznikat v širokém rozsahu rychlostí zahrnujícím i transsonickou oblast. V této oblasti je ovlivněna zejména rychlost, při níž dochází k třepetání, a to vlivem nelineárních jevů v proudu. Běžné nástroje, které jsou založeny na lineárních teoriích, nejsou schopny tyto nelineární jevy popsat. Cílem práce je proto navrhnout, implementovat a otestovat nástroj pro výpočetní (numerickou) simulaci aeroelasticity. Nástroj má využívat řešič proudového pole, který je schopen předpovědět nelineární jevy. V práci je kladen důraz na simulaci statické aeroelasticity. V práci jsou popsány metody, které je nutno zahrnout do numerické simulace statické aeroelasticity. Dále je popsán vlastní nástroj a je provedeno zhodnocení konvergence statických aeroelastických výpočtů. Funkčnost nástroje byla ověřena na příkladech, kdy byly použity různé aerodynamické a strukturální modely. Nástroj byl také aplikován při aerodynamické tvarové optimalizaci poddajného křídla. Výsledky optimalizace a její výpočetní náročnost byly porovnány s případem optimalizace tuhého křídla. Na závěr je v práci prezentován příspěvek autora do výzkumu zaměřeného na zhodnocení vlivu časové synchronizace mezi CFD a CSM řešiči. Použitý testovací případ je transsonické obtékání křídla na začátku třepetání (flutteru). Výsledky byly srovnány s experimentálními daty poskytnutými NASA.
28
Chae, Seungmook. "Effect of Follower Forces on Aeroelastic Stability of Flexible Structures." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5037.
Full textAbstract:
Missile bodies and wings are typical examples of structures that can be represented by beam models. Such structures, loaded by follower forces along with aerodynamics, exhibit the vehicle's aeroelastic instabilities. The current research integrates a nonlinear beam dynamics and unsteady aerodynamics to conduct aeroelastic studies of missile bodies and wings subjected to
follower forces. The structural formulations are based on a geometrically-exact, mixed finite element method. Slender-body theory and thin-airfoil theory are used for the missile aerodynamics, and two-dimensional finite-state unsteady aerodynamics is used for wing aerodynamics. The aeroelastic analyses are performed using time-marching scheme for the missile body stability, and eigenvalue analysis for the wing flutter, respectively. Results from the time-marching formulation agree with published results for dynamic stability and show the development of limit cycle oscillations for disturbed flight near and above the critical thrust. Parametric studies of the aeroelastic behavior of specific flexible missile configurations are presented, including effects of flexibility on stability, limit-cycle amplitudes, and missile loads. The results do yield a significant interaction between the thrust, which is a follower force, and
the aeroelastic stability. Parametric studies based on the eigenvalue analysis for the wing
flutter, show that the predicted stability boundaries are very sensitive to the ratio of bending stiffness to torsional stiffness. The effect of thrust can be either stabilizing or
destabilizing, depending on the value of this parameter. An assessment whether or not the magnitude of thrust needed to influence the flutter speed is practical is made for one
configuration. The flutter speed is shown to change by 11% for this specific wing configuration.
29
Alan, Luton J. "Numerical simulations of subsonic aeroelastic behavior and flutter suppression by active control /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-03172010-020348/.
Full text
30
Bernardi, Giacomo. "Feasibility Study of a 3D CFD Solution for FSI Investigations on NREL 5MW Wind Turbine Blade." Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159690.
Full textAbstract:
With the increase in length of wind turbine blades flutter is becoming a potential design constrain, hence the interest in computational tools for fluid-structure interaction studies. The general approach to this problem makes use of simplified aerodynamic computational tools. Scope of this work is to investigate the outcomes of a 3D CFD simulation of a complete wind turbine blade, both in terms of numerical results and computational cost. The model studied is a 5MW theoretical wind turbine from NREL. The simulation was performed with ANSYS-CFX, with different volume mesh and turbulence model, in steady-state and transient mode. The convergence history and computational time was analyzed, and the pressure distribution was compared to a high fidelity numerical result of the same blade. All the model studied were about two orders of magnitude lighter than the reference in computation time, while showing comparable results in most of the cases. The results were affected more by turbulence model than mesh density, and some turbulence models did not converge to a solution. In general seems possible to obtain good results from a complete 3D CFD simulation while keeping the computational cost reasonably low. Attention should be paid to mesh quality.
31
Engelsen, Frode. "Design-oriented gust stress contraints for aeroservoelastic design synthesis /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9965.
Full text
32
Yoo, Kyung M. "Unsteady vortex lattice aerodynamics for rotor aeroelasticity in hover and in forward flight." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/11961.
Full text
33
Fuhrer, Christopher [Verfasser]. "Numerical Investigation on Spontaneous Condensation in Low-Pressure Steam Turbine Aeroelasticity / Christopher Fuhrer." Düren : Shaker, 2021. http://d-nb.info/1238497632/34.
Full text
34
Walsh, Justin M. "Composite material bend-twist coupling for wind turbine blade applications." Laramie, Wyo. : University of Wyoming, 2009. http://proquest.umi.com/pqdweb?did=1965523621&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Full text
35
Nichkawde, Chetan. "Nonlinear aeroelastic analysis of high aspect-ratio wings using the method of numerical continuation." Texas A&M University, 2003. http://hdl.handle.net/1969.1/3846.
Full textAbstract:
This research explores the impact of kinematic structural nonlinearities on the
dynamics of a highly deformable cantilevered wing. Two different theoretical formulations
are presented and analysed for nonlinear behavior. The first formulation, which
is more conventional, assumes zero equilibrias and structural nonlinearities occur as
terms up to third order in the Taylor series expansion of structural nonlinearities.
In the second approach, no prior assumption about equilibria states of the wing is
made. Kinematic nonlinearities due to curvature and inertia were retained in their
exact form. Thus, the former becomes a special case of the latter. This nonlinear formulation
permits the analysis of dynamics about nonzero trims. Nonzero trim states
are computed as a system parameter is varied using a continuation software tool. The
stability characteristics of these trim states are also ascertained. Various bifurcation
points of the system are determined. Limit-cycle oscillations are also investigated for
and are characterized in terms of amplitude of vibration. The research in particular
examines the impact of in-plane degree of freedom on the stability of nonzero trim
states. The effect of variation of system parameters such as stiffness ratio, aspect
ratio and root angle of attack is also studied. The method of direct eigenanalysis of
nonzero equilibria is novel and new for an aeroelastic system.
36
Monaco, Lucio. "PARAMETRIC STUDY OF THE EFFECT OF BLADE SHAPE ON THE PERFORMANCE OF TURBOMACHINERY CASCADES : PART III A: AERODYNAMIC DAMPING BEHAVIOUR – COMPRESSOR PROFILES." Thesis, KTH, Kraft- och värmeteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-131210.
Full text
37
Schuster, D. M. (David M. ). "Application of an aeroelastic analysis method for aerodynamic improvement of fighter wings at maneuver flight conditions." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/12367.
Full text
38
Zink, Paul Scott. "A methodology for robust structural design with application to active aeroelastic wings." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12424.
Full text
39
Shang, Xiaoyang. "Aeroelastic stability of composite hingeless rotors with finite-state unsteady aerodynamics." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/12543.
Full text
40
Kim, ChangEun. "Static and dynamic aeroelastic simulation of wings with state space aerodynamic models." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/12898.
Full text
41
Smith, Marilyn Jones. "A fourth order Euler/Navier-Stokes prediction method for the aerodynamics and aeroelasticity of hovering rotor blades." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/13058.
Full text
42
Hashemi-kia, Mostafa. "Dynamic testing techniques and applications for an aeroelastic rotor test facility." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/13887.
Full text
43
Camara, Enrique. "Validation of Time Domain Flutter PredictionTool with Experimental Results." Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160541.
Full textAbstract:
In turbomachinery applications as propulsion and power generation, there is a continuous endeavour to design engines with higher efficiency, driving the compressor and turbine blades towards slimmer and more aerodynamically loaded configurations that frequently operate with fluids at higher temperatures and speeds. This combination of reduced design space and adverse operating environment makes the blades more susceptible to flutter and challenges the designer to predict its occurrence. Nowadays there are different CFD solvers that allow the prediction of flutter in turbomachinery; some of them are more efficient than others and provide considerable computational power savings when compared with traditional CFD methods that sometimes require the simulation of several or all the blades in a given row. The present thesis work is aimed at investigating the strengths and potential limitations of a novel time marching method for Flutter prediction in the Travelling Wave Mode (TWM) domain available in ANSYS CFX 14.5. The results are compared with experimental measurements obtained at the KTH test rig and CFD simulations in the Influence Coefficient Domain (INFC) performed in a previous MSc. Thesis in 2013. An approach in CFX to solve flutter is the Fourier Transformation method that uses only two passages with phase lagged periodic boundary conditions. In the previous thesis only one operating point was calculated using this method. This project focuses on the extension of the calculations to various operating points and expanding the solver validation.Thesis work done at Siemens Industrial Turbomachinery, Finspang, Sweden.
44
Bell, David Lloyd. "Three dimensional unsteady flow for an oscillating turbine blade." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4794/.
Full textAbstract:
An experimental and computational study, motivated by the need to improve current understanding of blade flutter in turbomachinery and provide 3D test data for the validation of advanced computational methods for the prediction of this aeroelastic phenomenon, is presented. A new, low speed flutter test facility has been developed to facilitate a detailed investigation into the unsteady aerodynamic response of a turbine blade oscillating in a three dimensional bending mode. The facility employs an unusual configuration in which a single turbine blade is mounted in a profiled duct and harmonically driven. At some cost in terms of modelling a realistic turbomachinery configuration, this offers an important benefit of clearly defined boundary conditions, which has proved troublesome in previous work performed in oscillating cascade experiments. Detailed measurement of the unsteady blade surface pressure response is enabled through the use of externally mounted pressure transducers, and an examination of the techniques adopted and experimental error indicate a good level of accuracy and repeatability to be attained in the measurement of unsteady pressure. A detailed set of steady flow and unsteady pressure measurements, obtained from five spanwise sections of tappings between 10% and 90% span, are presented for a range of reduced frequency. The steady flow measurements demonstrate a predominant two-dimensional steady flow, whilst the blade surface unsteady pressure measurements reveal a consistent three dimensional behaviour of the unsteady aerodynamics. This is most especially evident in the measured amplitude of blade surface unsteady pressure which is largely insensitive to the local bending amplitude. An experimental assessment of linearity also indicates a linear behaviour of the unsteady aerodynamic response of the oscillating turbine blade. These measurements provide the first three dimensional test data of their kind, which may be exploited towards the validation of advanced flutter prediction methods. A three dimensional time-marching Euler method for the prediction of unsteady flows around oscillating turbomachinery blades is described along with the modifications required for simulation of the experimental test configuration. Computationalsolutions obtained from this method, which are the first to be supported by 3D test data, are observed to exhibit a consistently high level of agreement with the experimental test data. This clearly demonstrates the ability of the computational method to predict the relevant unsteady aerodynamic phenomenon and indicates the unsteady aerodynamic response to be largely governed by inviscid flow mechanisms. Additional solutions, obtained from a quasi-3D version of the computational method, highlight the strong three dimensional behaviour of the unsteady aerodynamics and demonstrate the apparent inadequacies of the conventional quasi-3D strip methodology. A further experimental investigation was performed in order to make a preliminary assessment of the previously unknown influence of tip leakage flow on the unsteady aerodynamic response of oscillating turbomachinery blades. This was achievedthrough the acquisition of a comprehensive set of steady flow and unsteady pressure measurements at three different settings of tip clearance. The steady flow measurements indicate a characteristic behaviour of the tip leakage flow throughout the range of tip clearance examined, thereby demonstrating that despite the unusual configuration, the test facility provides a suitable vehicle for the investigation undertaken. The unsteady pressure data show the blade surface unsteady pressure response between 10% and 90% span to be largely unaffected by the variation in tip clearance. Although close examination of the unsteady pressure measurements reveal subtle trends in the first harmonic pressure response at 90% span, which are observed to coincide with localised regions where the tip leakage flow has a discernible impact on the steady flow blade loading characteristic. Finally, some recommendations for further work are proposed
45
Ricciardi, Anthony Pasquale. "Utility of Quasi-Static Gust Loads Certification Methods for Novel Configurations." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35359.
Full textAbstract:
Aeroelastic gust and maneuver loads have driven the sizing of primary aircraft structures since the beginning of aviation. Methodologies for determining the gust loads on aircraft have evolved over the last 100 years. There are three general approaches to gust loads analysis: quasi-static, transient, and continuous methods. Quasi-static analysis offers the greatest computational efficiency. A quasi-static formulation referred to as Pratt's Method is the current practice for FAR Part 23 certification requirements. Assumptions made in the derivation of Pratt's Method are acceptable for many conventional aircraft, but additional fidelity from transient and continuous analysis are required to certify FAR Part 25 aircraft.
This work provides an assessment of the usability of Pratt's Method for unconventional high altitude long endurance (HALE) aircraft. Derivation Pratt's Method is reviewed and all assumptions are identified. Error of a key curve fit equation is quantified directly. Application dependent errors are quantified by comparing loads calculated using Pratt's Method to loads calculated from transient analysis. To facilitate this effort, a state of the art nonlinear aeroelastic code has been modified to more accurately capture the transient gust response.
Application dependent errors are presented in the context of a SensorCraft inspired joined-wing HALE model, and a Helios inspired flying wing HALE model. Recommendations are made on the usability of Pratt's Method for aircraft similar to the two HALE models. It is concluded that Pratt's Method is useful for preliminary design of the joined-wing HALE model, but inadequate for the analysis of the flying wing model. Additional recommendations are made corresponding to subtleties in the implementation of Pratt's Method for unconventional configurations.Master of Science
46
Ricciardi, Anthony Pasquale. "Geometrically Nonlinear Aeroelastic Scaling." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/24913.
Full textAbstract:
Aeroelastic scaling methodologies are developed for geometrically nonlinear applications. The new methods are demonstrated by designing an aeroelastically scaled model of a suitably nonlinear full-scale joined-wing aircraft. The best of the methods produce scaled models that closely replicate the target aeroelastic behavior. Internal loads sensitivity studies show that internal loads can be insensitive to axial stiffness, even for globally indeterminate structures. A derived transverse to axial stiffness ratio can be used as an indicator of axial stiffness importance. Two findings of the work extend to geometrically linear applications: new sources of local optima are identified, and modal mass is identified as a scaling parameter. Optimization procedures for addressing the multiple optima and modal mass matching are developed and demonstrated. Where justified, limitations of commercial software are avoided through development of custom tools for structural analysis and sensitivities, aerodynamic analysis, and nonlinear aeroelastic trim.Ph. D.
47
Eger, Charles Alfred Gaitan. "Design of a Scaled Flight Test Vehicle Including Linear Aeroelastic Effects." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23088.
Full textAbstract:
A procedure for the design of a scaled aircraft using linear aeroelastic scaling is developed and demonstrated. Previous work has shown the viability in matching scaled structural frequencies and mode shapes in order to achieve consistent linear scaling of simple models. This methodology is adopted for use on a high fidelity joined-wing aircraft model. Natural frequencies and mode shapes are matched by optimizing structural ply properties and nonstructural mass. A full-scale SensorCraft concept developed by AFRL and Boeing serves as the target model, and a 1/9th span geometrically scaled remotely piloted vehicle (RPV) serves as the initial design point. The aeroelastic response of the final design is verified against the response of the full-scale model. Reasonable agreement is seen in both aeroelastic damping and frequency for a range of flight velocities, but some discrepancy remains in accurately capturing the flutter velocity.Master of Science
48
Fagley, Casey P. "Reduced order models and control of large scale aero-elastic simulations." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1594493621&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Full text
49
Li, Sihao. "Effect of aeroelasticity in tow tank strain gauge measurements on a NACA 0015 airfoil." Ohio : Ohio University, 1993. http://www.ohiolink.edu/etd/view.cgi?ohiou1175713922.
Full text
50
Alexeev, Timur. "Computational aeroelasticity study of horizontal axis wind turbines with coupled bending - torsion blade dynamics." Thesis, University of California, Davis, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3614169.
Full textAbstract:
With the increasing size of wind turbines and the use of flexible and light materials in aerodynamic applications, aeroelastic tailoring for power generation and blade stability has become an important subject in the study of wind turbine dynamics. To this day, coupling of bending and torsion in wind turbine rotor blades has been studied primarily as an elastic mechanism due to a coupling laminate construction. In this report, inertial coupling of bending and torsion, due to offset of axis of elasticity and axis of center of mass, is investigated and numerical simulations are performed to test the validity of the constructed model using an in-house developed aeroelastic numerical tool. A computationally efficient aeroelastic numerical tool, based on Goldstein's helicoidal vortex model with a prescribed wake model and modal coupling of bending and torsion in the blades, is developed for 2-bladed horizontal axis wind turbines and a conceptual study is performed in order to argue the validity of the proposed formulation and numerical construction. The aeroelastic numerical tool, without bending-torsion coupling, was validated (Chattot 2007) using NREL Phase VI wind turbine data, which has become the baseline model in the wind turbine community. Due to novelty of the proposed inertial bending-torsion coupling in the aeroelastic model of the rotor and lack of field data, as well as, other numerical tools available for code to code comparison studies, a thorough numerical investigation of the proposed formulation is performed in order to validate the aeroelastic numerical tool Finally, formulations of geometrically nonlinear beams, elastically nonlinear plates and shells, and a piecewise linear, two degree of freedom, quasi steady, aerodynamic model are presented as an extension for nonlinear wind turbine aeroelastic simulations. Preliminary results of nonlinear beams, plates, shells, and 2 DOF NACA0012 aeroelastic model are presented.