The present research investigates the torsional Aeroelasticity of the blade of an H-type vertical axis wind turbine subject to stall and post-stall conditions in various Reynolds regimes, which is experienced by the blade in a full revolution. In order to simulate the aerodynamics, a new model based on a combination of the Double Multi Streamtubes (DMST) model and the nonlinear multi-criteria Cl- equations, which is depended on the local Reynolds number of the flow, has been proposed. The results indicate that using of multi-criteria function dependent on the Reynolds number for the Cl- curve has improved the prediction of the torsional behavior of the blade in azimuthal rotation of the blade compared to using single-criterion functions and linear aerodynamics. The blade’ s aeroelastic torsion has been studied for various TSR values.

Ground vibration test (GVT) is one of the standard structural tests required for designed passenger aircrafts. This test is performed to derive the experimental dynamical model of aircraft structure. The process of executing this test involves test planning, structural preparation, data gathering, and extraction of dynamic parameters from the test data. In the present study, the practical implementation process of each step is described. Given the size and complexity of this test, certain techniques, hardware, and software are to be investigated. The global experience of performing this test is briefly discussed. Finally, a typical setup for a ground vibration test of a large aircraft is introduced and described.

In this paper, supersonic flutter analysis of cantilevered trapezoidal plates composed of two functionally graded face sheets and an isotropic homogeneous core is presented. Using Hamilton’s principle, the set of governing equations and external boundary conditions are derived. A transformation of coordinates is used to convert the governing equations and boundary conditions from the original coordinates into the new dimensionless computational ones. Generalized differential quadrature method (GDQM) is employed as a numerical method and critical aerodynamic pressure and flutter frequencies are derived. Convergence, versatility, and accuracy of the presented solution are confirmed using numerical and experimental results presented by other authors. The effect of power- law index, thickness of the core, total thickness of the plate, aspect ratio and angles of the plate on the flutter boundaries are investigated. It is concluded that any attempt to increase the critical aerodynamic pressure leads to a decrease in lift force or rise in total weight of the plate.

A method is presented for the stress analysis of flight vehicles under different flight conditions including gust and control surface deflection (or maneuver) using the governing equations of rigid-body motions and elastic deformations. The Lagrangian approach is used to derive the governing equations of motions. For this purpose, the basic equations of motions are derived in terms of potential energy, kinetic energy and generalized forces, which are, in turn, computed in terms of rigid-body motion variables, elastic mode shapes and cla(x) distribution for aerodynamic forces. By replacing them into the relations obtained, the governing equations for aeroelastic behavior of the vehicle are derived. The system of aeroelastic equations of motions is solved in time domain using numerical methods. The stress distribution is determined using the relation between modal variables and strain at each point. Finally, the prepared code is verified through comparison of the results obtained from the proposed method for the stability of a rocket and the same results reported by other studies. Also additional information such as maximum stress in the body is presented for various flight conditions.

One of the special topics in the aeroelastic field is the flutter of the airplane wing at an index speed called the flutter speed, which, if this phenomenon is not controlled, there will be a possibility of destroying the structure (airplane wing). Various methods for wing control have been proposed in the last two decades. In the current research, two-way forced jet momentum embedded on the wing is used to control a pseudo three-dimensional wing with a simplified unsteady flow regime. The jet activation signal at the flutter speed is provided by the pulse width-pulse frequency modulator. The advantages of this modulator include its quasi-linear performance, high precision with the presence of fluctuations and flexibility. In this research, the double aeroelastic, non-reversible and rectangular (Hancock) wing model is considered, and the strip theory is used to develop the lift force during spinball. In the speed of the flutter ball, the swing of the wing is driven to damping by the jet activity, and according to the obtained aeroelastic graphs, satisfactory results have followed.

A combination of the control surface to the wing section is carried out by mechanisms which usually have free play. This leads to structural nonlinearity behavior and, as a result, nonlinear aeroelastic behavior. In this study, the aeroelastic behavior of an airfoil with a control surface, which, together, have three degrees of freedom; i.e.: heaving and pitching of the airfoil and pitching of the control surface, has been analyzed in a subsonic incompressible flow regime. A bilinear spring is employed to join the airfoil to the control surface and a quasi steady aerodynamic model is used for aerodynamic modeling. It is shown that the quasi steady aerodynamic model is not reliable for determination of the aeroelastic behavior and flutter boundary of the airfoil. However, the aeroelastic characteristics of the airfoil can be investigated using such a modeling approach. As another outstanding outline, it is concluded that. often, the instability is of a Limit Cycle Oscillation (LCO) type.

The aerodynamic of Vertical Axis Wind Turbine (VAWT) is more complex than a horizontal axis wind turbine. In the present research, the combination of the Wagner unsteady aerodynamic model, static stall and Double Multiple Stream Tube (DMST) aerodynamic model have been used to investigate the aeroelastic behavior of VAWT. For this purpose, the DMST aerodynamic model, which is related to the vertical axis wind turbine aerodynamics model, has been used to obtain two parameters of the angle of attack and relative velocity. Then these two parameters have been applied to the Wagner nonlinear aerodynamics, which considers the effect of the static stall. This flexible nonlinear presented model based on DMST is called NFDMST aerodynamic model. One-degree of freedom of typical section and two-degree of freedom model have been investigated for static Aeroelasticity and dynamic aeroelastic behavior, respectively. The VAWT blade experiences a variety of attack angles and relative velocity in a spin, so the goal is to obtain the instability velocity in a different position and consider the effect of aerodynamic and structure nonlinearity. The results show that the nonlinear aerodynamic model has accurate results and the aeroelastic design condition associated with-90degree azimuth angle, in which the minimum instability velocity is 45. 2m/s. In addition, the change of instability speed of rotating airfoil in a spin is about 6%.

The numerical simulation of near-stall condition in a passage of an isolated subsonic rotor is studied in detail. The requirements of numerical simulation in order to resolve turbulent spectra around the blade are studied. According to the fact that most of unsteady aerodynamic phenomena incept from blades leading edge, and the role of this part in types and intensity of instabilities, the goal of this paper is to investigate the effects of changes in radius of leading edge of airfoil on flow phenomena in different scales of wave numbers. The governing equations of flow-field are solved using different numerical approaches. Resolution characteristics of different modeling and simulation techniques are investigated. The primary geometry of blade uses a standard NACA-65 series airfoil, which has been tolerated by 50% variation in circular leading edge radius. Mesh requirements of flow simulation for intended purposes are studied in detail and some recommendations are proposed to be implemented in numerical aeroelastic simulations. Accuracy and fidelity of LES results are studied with extraction of power spectra around the blade and the portion of resolved energy is also estimated. Results suggest that the order of accuracy and grid density highly affect the small-scale flow phenomena. The variations in leading edge radius also have great effect on energy distribution among resolved scales.