Search for: aeroelasticity
Total 77 records
Erratum: Discussion on active aeroelastic control of 2-D wing-flap systems operating in an incompressible flowfield and impacted by a blast pulse by Librescu et al., Journal of Sound and Vibration 283 (3-5) (2005) 685-706 (Journal of Sound and Vibration (2013) 332:13 (351-3358)), Article Journal of Sound and Vibration ; Vol. 333, Issue. 25 , 2014 , pp. 7084-7087 ; ISSN: 0022460X ; Firouz-Abadi, R. D ; Roshanian, J ; Ghaffari, A ; Sharif University of Technology
[No abstract available]
Analysis of non-linear aeroelastic response of a supersonic thick fin with plunging, pinching and flapping free-plays, Article Journal of Fluids and Structures ; Volume 40 , 2013 , Pages 163-184 ; 08899746 (ISSN) ; Alavi, S. M ; Salarieh, H ; Sharif University of Technology
The flutter of a 3-D rigid fin with double-wedge section and free-play in flapping, plunging and pitching degrees-of-freedom operating in supersonic and hypersonic flight speed regimes have been considered. Aerodynamic model is obtained by local usage of the piston theory behind the shock and expansion analysis, and structural model is obtained based on Lagrange equation of motion. Such model presents fast, accurate algorithm for studying the aeroelastic behavior of the thick supersonic fin in time domain. Dynamic behavior of the fin is considered over large number of parameters that characterize the aeroelastic system. Results show that the free-play in the pitching, plunging and flapping...
Novel aspects of elastic flapping wing: analytical solution for inertial forcing, Article Advances in Aircraft and Spacecraft Science ; Volume 5, Issue 3 , May , 2018 , Pages 335-348 ; 2287528X (ISSN) ; Pourtakdoust, S. H ; Bighashdel, A ; Sharif University of Technology
Techno Press 2018
The structural dynamics (SD) behavior of Elastic Flapping Wings (EFWs) is investigated analytically as a novel approach in EFWs analysis. In this regard an analytical SD solution of EFW undergoing a prescribed rigid body motion is initially derived, where the governing equations are expressed in modal space. The inertial forces are also analytically computed utilizing the actuator induced acceleration effects on the wing structure, while due to importance of analytical solution the linearity assumption is also considered. The formulated initial-value problem is solved analytically to study the EFW structural responses, where the effect of structure-actuator frequency ratio,...
Development of an aeroelastic model based on system identification using boundary elements method, Article Aircraft Engineering and Aerospace Technology ; 2021 ; 17488842 (ISSN) ; Borhan Panah, M. R ; Sharif University of Technology
Emerald Group Holdings Ltd 2021
Purpose: The purpose of this paper is to analyze the stability of aeroelastic systems using a novel reduced order aeroelastic model. Design/methodology/approach: The proposed aeroelastic model is a reduced-order model constructed based on the aerodynamic model identification using the generalized aerodynamic force response and the unsteady boundary element method in various excitation frequency values. Due to the low computational cost and acceptable accuracy of the boundary element method, this method is selected to determine the unsteady time response of the aerodynamic model. Regarding the structural model, the elastic mode shapes of the shell are used. Findings: Three case studies are...
Chaotic analysis of nonlinear viscoelastic panel flutter in supersonic flow, Article Nonlinear Dynamics ; Volume 32, Issue 4 , 2003 , Pages 387-404 ; 0924090X (ISSN) ; Fazelzadeh, S. A ; Sharif University of Technology
In this paper chaotic behavior of nonlinear viscoelastic panels in a supersonic flow is investigated. The governing equations, based on von Kàrmàn's large deflection theory of isotropic flat plates, are considered with viscoelastic structural damping of Kelvin's model included. Quasi-steady aerodynamic panel loadings are determined using piston theory. The effect of constant axial loading in the panel middle surface and static pressure differential have also been included in the governing equation. The panel nonlinear partial differential equation is transformed into a set of nonlinear ordinary differential equations through a Galerkin approach. The resulting system of equations is solved...
Curvilinear fiber optimization tools for aeroelastic design of composite wings, Article Journal of Fluids and Structures ; Volume 33 , 2012 , Pages 180-190 ; 08899746 (ISSN) ; Zamani, Z ; Sharif University of Technology
The aeroelastic design of composite wings modeled as thin-walled beams is investigated through the use of curvilinear fiber. The structural model considers non-classical effects such as transverse shear, warping restraint, rotary inertia, nonuniform torsional model and also aerodynamic loads based on Wagner's function. In this paper, a linear spanwise variation of the fiber orientation resulting in a variable-stiffness structure is used to optimize the wing for maximum aeroelastic instability speed purpose, while manufacturing constraints are incorporated. Numerical results indicate improvements of aeroelastic stability of variable-stiffness wings over conventional, constant-stiffness ones
Effect of thrust on the aeroelastic instability of a composite swept wing with two engines in subsonic compressible flow, Article Journal of Fluids and Structures ; Volume 36 , 2013 , Pages 18-31 ; 08899746 (ISSN) ; Askarian, A. R ; Zarifian, P ; Sharif University of Technology
This paper aims to investigate aeroelastic stability boundary of subsonic wings under the effect of thrust of two engines. The wing structure is modeled as a tapered composite box-beam. Moreover, an indicial function based model is used to calculate the unsteady lift and moment distribution along the wing span in subsonic compressible flow. The two jet engines mounted on the wing are modeled as concentrated masses and the effect of thrust of each engine is applied as a follower force. Using Hamilton's principle along with Galerkin's method, the governing equations of motion are derived, then the obtained equations are solved in frequency domain using the K-method and the aeroelastic...
Evaluation of flapping wing propulsion based on a new experimentally validated aeroelastic model, Article Scientia Iranica ; Volume 19, Issue 3 , 2012 , Pages 472-482 ; 10263098 (ISSN) ; Aliabadi, S. K ; Sharif University of Technology
To evaluate the propulsion system capabilities of a Flapping Micro Air Vehicle (FMAV), a new aeroelastic model of a typical flexible FMAV is developed, utilizing the Euler-Bernoulli torsion beam and quasi steady aerodynamic model. The new model accounts for all existing complex interactions between the mass, inertia, elastic properties, aerodynamic loading, flapping amplitude and frequency of the FMAV, as well as the effects of several geometric and design parameters. To validate the proposed theoretical model, a typical FMAV, as well as an instrumented test stand for the online measurement of forces, flapping angle and power consumption, has been constructed. The experimental results are...
Aeroelastic Analysis of Sandwich wing With Fractional Viscoelastic Core, M.Sc. Thesis Sharif University of Technology ; Haddadpour, Hassan
In this research, the effect of application of viscoelastic material with fractional derivatives pattern in aeroelastic stability analysis for a sandwich wing, has been examined. In order to study the wing’s aeroelastic behavior and the effect of inner layer on aeroelastic instability boundaries (fluttering), the wing is modeled as a cantilever sandwich beam with a fractional viscoelastic core. The Wagner approximation is used for applying the unstable aeroelastic loads. To obtain the characteristics and behaviors of the structure some assumptions including non-classical effects, are considered. These non-classical effects are the inner layer shear stress, the axial movements, the wing’s...
Viscous damping effect on the aeroelastic stability of subsonic wings: Introduction of the U–K method, Article Journal of Fluids and Structures ; Volume 73 , 2017 , Pages 1-15 ; 08899746 (ISSN) ; Dehghani Firouz Abadi, R ; Rahmanian, M ; Sharif University of Technology
This study aims at introduction of a novel method for evaluating the effect of viscous damping on the aeroelastic stability boundaries. The K-method is well-known for being one of the fastest methods in determining the instability conditions (i.e. critical speed and its corresponding frequency). However, formulation of the K-method is developed for aeroelastic systems without viscous damping and solution is valid where the introduced artificial damping is zero. Taking into account the framework of the K-method in general, this study has tried to remove the major shortcoming of the K-method, i.e. investigation of the effect of viscous damping on the aeroelastic stability boundaries. The...
Aeroelastic stability and response of composite swept wings in subsonic flow using indicial aerodynamics, Article Journal of Vibration and Acoustics, Transactions of the ASME ; Volume 135, Issue 5 , 2013 ; 10489002 (ISSN) ; Farsadi, T ; Haddadpour, H ; Sharif University of Technology
In this study, the aeroelastic stability and response of an aircraft swept composite wing in subsonic compressible flow are investigated. The composite wing was modeled as an anisotropic thin-walled composite beam with the circumferentially asymmetric stiffness structural configuration to establish proper coupling between bending and torsion. Also, the structural model consists of a number of nonclassical effects, such as transverse shear, material anisotropy, warping inhibition, nonuniform torsional model, and rotary inertia. The finite state form of the unsteady aerodynamic loads have been modeled based on the indicial aerodynamic theory and strip theory in the subsonic compressible flow....
Stability analysis of elastic launch vehicles with fuel sloshing in planar flight using a BEM-FEM model, Article Aerospace Science and Technology ; Volume 53 , 2016 , Pages 74-84 ; 12709638 (ISSN) ; Haddadpour, H ; Ebrahimian, M ; Sharif University of Technology
Elsevier Masson SAS 2016
A numerical model is developed for investigation of coupled dynamics of fuel contained elastic launch vehicles in planar atmospheric flight. Finite element method along with the linear quasi-steady piston aerodynamic theory is used for developing an aeroelastic model. A reduced order boundary element model is used for modeling the liquid sloshing in tanks. The interaction of sloshing and aeroelasticity is studied using stability analysis of the coupled system. Results show that the slosh-aeroelastic coupling in an elastic launch vehicle occurs for low tank filling ratios and may lead to decreasing the system damping. Due to more interactions between the slosh and rigid body modes, larger...
True damping and frequency prediction for aeroelastic systems: The PP method, Article Journal of Fluids and Structures ; Volume 25, Issue 7 , 2009 , Pages 1177-1188 ; 08899746 (ISSN) ; Firouz Abadi, R. D ; Sharif University of Technology
This paper presents a numerical scheme for stability analysis of the aeroelastic systems in the Laplace domain. The proposed technique, which is called the PP method, is proposed for when the aerodynamic model is represented in the Laplace domain and includes complicated transcendental expressions in terms of the Laplace variable. This method utilizes a matrix iterative procedure to find the eigenvalues of the system and generalizes the other methods such as the P and PK methods for prediction of the flutter conditions. The major advantage of this technique over the other approximate methods is true prediction of subcritical damping and frequency values of the aeroelastic modes. To examine...
Unsteady supersonic aerodynamics based on BEM, including thickness effects in aeroelastic analysis, Article Journal of Fluids and Structures ; Volume 19, Issue 6 , 2004 , Pages 801-813 ; 08899746 (ISSN) ; Esfahanian, V ; Haddadpour, H ; Behbahani Nejad, M ; Sharif University of Technology
A general three-dimensional aeroelastic solver is developed based on coupled finite element and boundary element methods and applied to investigate the flutter boundaries in supersonic flows. The boundary element method is applied to three-dimensional unsteady supersonic potential flow as the aerodynamic model and coupled with the finite element method for structural modelling, in order to construct the system of aeroelastic equations. The aeroelastic equations are solved for the flutter prediction using the frequency domain approach. Flutter boundaries for two types of wing planforms at supersonic speeds are determined and compared with the existing experimental results and previous...
Aeroelastic Topology Optimization of a Supersonic Wing, M.Sc. Thesis Sharif University of Technology ; Hadadpour, Hassan ; Dehghani Firouzabadi, Rouhollah ; Noorian, Mohammad Ali
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...
Development of the Hale Aircraft's Aeroelastic Model with Very Flexible Wings, Ph.D. Dissertation Sharif University of Technology ; Dehghani Firouzabadi, Roohallah
In this study, a nonlinear aeroelastic model for an aircraft with fully flexible wings is obtained. This aeroelastic model is based on system identification and is created using the beam model for the structure and the three-dimensional panel method for aerodynamic analysis. The model intended for the structure is a nonlinear beam with exact geometry with initial deformation and rigid motion. The model intended for aerodynamics is an unsteady three-dimensional panel method for the airplane’s body, wings, and tail. The desired aeroelasticity model is a reduced-order model based on system identification using the time-domain/frequency-domain aerodynamic response under forced vibrations in the...
On dynamic instability of a pressurized functionally graded carbon nanotube reinforced truncated conical shell subjected to yawed supersonic airflow, Article Composite Structures ; Volume 153 , 2016 , Pages 938-951 ; 02638223 (ISSN) ; Asadi, H ; Wang, Q ; Sharif University of Technology
The aeroelastic flutter characteristics of a functionally graded carbon nanotube reinforced composite (FG-CNTRC) truncated conical shell under simultaneous actions of a hydrostatic pressure and yawed supersonic airflow are scrutinized. The nonlinearity in geometry of the conical shell is considered in Green–Lagrange sense and the model is derived according to the Novozhilov nonlinear shell theory. The aerodynamic pressure is modeled based on the quasi-steady Krumhaar's modified supersonic piston theory by considering the effect of the panel curvature and flow yaw angle. Parametric studies are conducted to investigate the effects of boundary conditions, semi-vertex angle, distribution and...
Aerodynamic Investigation of an Aeroelastic Flapping Wing and Optimum Design Method, Ph.D. Dissertation Sharif University of Technology ; Mazaheri, Karim
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...
Study of Aeroelastic Instability at a Panel Located in a Fully Filled Fuel Tank Wall, M.Sc. Thesis Sharif University of Technology ; Dehghani Firouz-Abadi, Rouhollah
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...
Sharp edge gust effects on aeroelastic behavior of a flexible wing with high aspect ratio, Article 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, NV, 10 January 2005 through 13 January 2005 ; 2005 , Pages 14279-14293 ; Shams, Sh ; Kheiri, M ; Sharif University of Technology
The subject of the present paper is the investigation of the sharp edged gust effects on the aeroelastic behavior of a flexible wing. It is important to determine the response of the wing to the atmospheric turbulences during normal flight. So, linear modal analysis technique and linear quasi-steady aerodynamic are used for structural modeling and aerodynamic loading, respectively. Also, Lagrange method is used to obtain the system of equations of motion. Using the normal modes of free vibration, structural and aerodynamic matrices can be constructed. Then the aeroelastic instability of the system is determined using p method. Kussner function is used to model the sharp gust effects on the...