Sharif Digital Repository

In this research, an anistropic thin-walled beam composite is used to consider the effects of fiber orientation and lay-up configuration on the aeroelastic stability and response of an aircraft wing. The circum ferentially asymmetric stiffness (CAS) model consists of a group of non-classical effects; such as transverse shear, material anisotropic, warping inhibition, etc. The aerodynamic load has been modeled based on the strip theory and compressible unsteady flow in the finite- state form. In addition, to form the mass, stiffness and damping matrices of non-conservative aeroelastic systems the extended Galerkin’s method (EGM) and the method of separation of variables has been used. After... 

In the present work the stability analysis for the coupled aeroelasticity and fuel sloshing in supersonic wings is represented. The wing and store structure is modeled using the finite element method. The supersonic wing aerodynamic is modeled by the linear piston theory and store aerodynamic is modeled by the semi-stable slender body piston theory. Fuel sloshing in the store with desired geometry is modeled by the boundary element method. The coupled structure, aerodynamic and sloshing governing equations are drawn by using the Galerkin method and reduce order modeling teqnique for them and an effective numerical model was developed that is capable to analyze the stability for... 

Aeroelasticity analysis and prediction of wind turbines sturcture deformations are fundamental parts in their design. Increasing the size of wind turbine blades and development of Mega-watt sized wind turbines have enhanced the importance of these studies. In this study, the aeroelasticity analysis of a wind turbine blade has been done based on flexible multibody dynamics method. For this purpose, the modal approach has been used for modeling blade structure which has been considered as a flexible beam with bending and torsion degrees of freedom. The unsteady vortex lattice method has been used to calculate aerodynamic loads in order to combine with wind turbine blade structure model. Using... 

Nowadays Aeroelasticity is one of most important branch of aerospace science. The Aeroelastic analysis and get on aeroelastic safety margin, is one of the major steps that must be taken in flying crafts design. Diverse software have been developed for this purpose. Due to the increasing the demands of use of composite materials in aircraft structures, need to examine the effect of various parameters such as angles and stacking sequence on the aeroelastic instability (flutter and divergence) composite aircraft structures is determined. The analysis of wind turbines as a means of extracting energy from the wind and having a large diameter blades, causing the interference effects of aerodynamic... 

Aiming to improve the extraction performance of wind energy has led to the noticeable increase of the structural dimensions in the modern wind turbines. The larger blade with more flexibility experiences large structural deformation even under nominal operational loading, so the nonlinear modeling and analysis of these structures have become as important subject of the recent wind turbine researches. In this dissertation, the geometrical exact model of the rotating wind turbine blade under the effects of the tower tip's motion, and also the operational loading comprising the aerodynamic and gravitational loadings is presented. In this way, the geometrical exact beam formulation is developed... 

This dissertation presents aeroelastic stability analysis (flutter) pertinent to the complete flexible aircraft based on analytical dynamics, structural dynamics and aerodynamics. The unified formulation is based on fundamental principles and incorporates in a natural manner both rigid body motions of the aircraft as a whole and elastic deformations of the flexible components (fuselage, wing and empennage), as well as the aerodynamic, propulsion and gravity forces. The aircraft motion is described in terms of three translations and three rotations of a reference frame attached to the undeformed fuselage, and acting as aircraft body axes, and elastic displacements of each of the flexible... 

A series of algorithms developed for performing aeroelastic topology optimization applying stress constraint on a three dimentional structure of a supersonic wing. The structure modeled using finite element method by three dimentional solid hexahedron elements. Bi-directional evolutionary structural optimization method used for developing optimization algorithms. In order to apply supersonic aerodynamic loading and developing aeroelastic model algorithms, the piston aerodynamic theory utilized. In order to apply static pressure loading, the maximum angle of attack of the wing performance is proposed. Using developed MATLAB code by modeling and meshing wing structure in ABAQUS a software... 

In order to investigaton of dynamics behavior and determination of the aeroelastic stability of the turbomachine blade. the turbomachine blade is modeled by using the beam model, taking into account all degrees of freedom, the effect of warping, rotation and seting angle. For aerodynamic modeling, the Smith and Whitehead models are used which are valid in subsonic flow. The validity of the derived formulation is confirmed through comparison with those obtained from the finite element software and the available results in the literature. Then, by using the state feedback controller, the effect of sensor and piezoelectric actuator on the vibrations reduction of the structure and increasing the... 

Study of the structural flexibility of large-scale wind turbine components on aeroelastic performance is important under the existence of critical atmospheric conditions. Prediction and control the critical deformations, identifying maximum local deformation and modeling the forces involved, are required. Aeroelasticity analysis is a suitable method for studying the coupling effects of wind turbine aerodynamics, dynamics and structures. This research has been done by modeling wind turbine components including blades, hub, nacelle and tower, taking into account aerodynamic couplings, dynamics and structures. Considering the large scale of reference wind turbine, nonlinear equations have added... 

A complete 6DOF flight dynamic model of an elastic flapping wing (EFW), integrated with unsteady aerodynamic theory is developed. In this respect, initially efficient high fidelity modules for EFW structural dynamics (SD) as well as unsteady aerodynamics loadings (UAL) to be coupled with its flight dynamics are prepared. A modal approach is followed to model structural dynamics of plain and 3D EFWs. This is in contrast with the Euler-Bernoulli beam theory that is mostly utilized for SD in the existing literature. In addition, due to the possibility of large wing deformations as well as the existence of non-linear displacement regime for realistic EFW flights, non-linear modal approaches such... 

Flapping wing vehicles produce aerodynamic lift and thrust through the flapping motion of their wings. The dynamic performance of a flexible membrane flapping wing is experimentally investigated here. To investigate aeroelastic effects of flexible wings (specifically, wing’s twisting stiffness) on hovering and cruising aerodynamic performance, a flapping-wing system and an experimental setup were designed and built. This system measures the unsteady aerodynamic and inertial forces, power usage and angular speed of the flapping wing motion for different flapping frequencies, angles of attack, various wind tunnel velocities up to 12 m/s and for various wings with different chordwise... 

In this thesis, effects of bending and torsional elasticity of a flapping wing on its average lift and input power are studied, using a semi-analytic method. Bending stiffness and torsional rigidity of wing spar, wing mass ratio and chordwise and spanwise center of gravity, also spar location are considered as variables for controlling elastic behavior of the wing.Governing integral equation is derived using Hamilton principle via modified quasi aerodynamic and linear Green-Lagrange strain tensor. Also an idealized flapping pattern is used to maximize average acceleration during each cycle. Next, integral equation is converted to a set of ordinary differential equations by means of Galerkin... 

Propulsive efficiency of flapping wings is optimized via a combination of flapping and elastic wing behavior. In this thesis, a complex complete model of flapping air vehicles (FAV) is developed in order to simulate the wing aeroelastic behavior. The resulting model is in the form of a complex set of partial differential equations whose solution is only numerically possible. Using the resulting simulation model, the different flapping behavior of the right and left wings can also be evaluated along with the resulting forces and moments that make the FAV flight realizable. One of the key flight conditions considered in many simulations is that of cruise flight. In order to have a... 

In this research, aeroelastic model of an elastic flapping wing has been derived in order to be integrated with the flight dynamic model. The model developed in this research well describes the coupled and nonlinear behavior of the passive torsional deformations of the wing during flapping motion. Based on this obtained equations, a precise propulsion model proper for flapping wing vehicles has been introduced. The effect of geometric and mechanical properties of the wing is being accounted. In order to validation of the analytical model several FMAVs as well as an instrumented test stand for online measurements of forces, flapping angle and power consumption have been designed and built... 

In the present work, the aeroelastic stability analysis for the swept taper wing and external fuel tank combination system in subsonic compressible flow are represented. The wing structure is modeled by using the Euler-Bernoulli beam theory. Fuel sloshing is modeled by using an equivalent mechanical mass-spring-damper model. Modal analysis technique is used to drive the structural equations of motion of the system. Aeorodynamic of wing is modeled by using index aerodynamic that has been dived by Marzocca and a slender body aerodynamic theory for the external fuel tank are used. For stability analysis, k-method redrived for a case that structural damping there is. The effects of the external... 

At this project we proceed to aero elastic modelling of a flapping wing using unsteady aerodynamic approach. Solving this model according to aerodynamic and structure coupling needs to simultaneously solve of aerodynamic and wing structure. Left side and right side of wing, each on divided into 18 elements. each element is interacting with sides element in terms of structural force and moment. In this modeling aerodynamic was modeling with unsteady aerodynamic approach (using modify theodersen function), also structure is flexible in to direction, bending and twisting. In the following it is proved that with change in flapping pattern better performance can be achieved. the effect of change... 

This dissertaion deals with the vibration and aeroelasticity analysis of a turbomachinery cascade with Magnetorheological Elastomer (MRE) based sandwich blades. At first, bending vibration of the rotary blades equipped with an MRE core based on the three-layered sandwich beam theory have been studied in the flexural and edgewise directions. Further, the torsional vibration is investigated and the effects of different parameters such as the intensity of the magnetic field, rotating speed and the MRE layer thickness on the natural frequencies and loss factors of the system are studied. On the basis of the modeling obtained for the structural dynamics and based on the Whitehead's unsteady... 

The aeroelastic behavior of wings made of functionally graded materials in supersonic flow is studied. For this purpose the flutter speed is calculated and in the next step the post flutter behavior is investigated. The structural model is based on the classical plate theory and material properties are assumed to be graded in the thickness direction according the power law distribution in terms of the volume fraction of material constituents. The linear piston theory which is modified to include thickness effects is used for supersonic aerodynamic modeling. The nonlinear structural model based on the Von-Karman strains is considered for prediction of the post-flutter behavior of the wing.... 

One of the classic problems in the aeroelasticity field is panel Fluttr that occurs in supersonic flow. Panels as wing skins, fuselage missile, and so are prone to this phenomenon, which causes fatigue and structures, will be demolished.In many cases, the wall panels and a full tank of fuel, this in this case, the vibration of the fluid-filled panels will be affected. There is clearly fluid into a tank filled with considering the approximation of incompressible fluid dynamics and vibration modes of the panel will change. In this study, a three-dimensional rectangular tank is considered the high walls on the elastic and supersonic flow passes.Fuel density and structural dimensions of Full... 

This study considers the flutter analysis rotating blade of a turbo machinery made of magneto rheological elastomer core. The Smith theory is used for modeling the compressible subsonic flow. The classical Hamilton’s principle along with the assume mode method is used to set up the equations of motion. The validity of the derived formulation is confirmed through comparison with those obtained from the finite element software and the available results in the literature. Various parametric studies including the effects of applied magnetic field, core layer thicknesses, rotating speed, setting angle are examined for considered configuration of the rotating blade. The results show that the first...