Dynamic Flutter Research Articles

Location Based Waste Management System Application Using Flutter

This project introduces a dynamic Flutter mobile application aimed at revolutionizing waste management in urban environments. The application leverages location-based services to provide users with real-time alerts regarding the arrival of garbage collectors, ensuring timely and efficient waste disposal. Additionally, it offers a feature to locate the nearest disposal facilities, catering to users who may be unfamiliar with proper waste management practices. The application's user-friendly interface and intuitive design aim to bridge the gap between residents and waste management authorities, ultimately fostering a more sustainable and organized waste management ecosystem in urban communities. This innovative solution exemplifies the potential of technology in addressing critical environmental challenges. Location-based waste management systems use GPS and other technologies to track waste collection and disposal activities. Location-based waste management systems can also help to educate the public about waste disposal practices and encourage recycling and composting

Stability of cantilever on elastic foundation under a subtangential follower force via shear deformation beam theories

Abstract The static stability of clamped-free columns resting on elastic foundation is investigated under a nonconservative subtangential follower force. The higher-order shear deformation beam theories are applied to treat structural instability of a clamped-free rectangular and circular beam resting on Winkler foundation. Based on Engesser's assumption, a single governing equation is derived for divergence instability of Beck cantilever under a subtangential follower force. For different warping shapes of rectangular and circular cross-sections, the critical divergence buckling loads are determined. Static buckling still occurs for a cantilever column subjected to a subtangential follower force with small nonconservativeness parameter and dynamic flutter instability occurs for large nonconservativeness parameter. In a free space, a unified relationship with the Euler buckling loads is given explicitly for the case of a dead load, and the buckling load has an apparent reduction due to shear deformation with different warping of the cross-section. The obtained results further modify the Euler buckling formula to suit for the columns with a broad range of slenderness. Elastic foundation nearly linearly increases the buckling load and a nonconservativeness parameter also raises the divergence buckling load. For shorter columns, the classical buckling loads are significantly overestimated. The effects of slenderness, warping shapes, nonconservativeness parameter, and spring stiffness coefficient are analyzed.

Analysis of dynamic response and flutter suppression system effectiveness of a long-haul aircraft in transonic flight mode

Analysis of dynamic response and flutter suppression system effectiveness of a long-haul aircraft in transonic flight mode

Rapid Method of Predicting the Subsonic Flutter Stability of AGTE Axial-Flow Compressor Blade Cascades. Part 1. Physical Backgrounds of the Method

Generalization of experimental investigation results for direct compressor cascades of blade profiles at a subsonic (continuous and separated) gas flow with bending, torsional, and bending-torsional vibrations created the basis for defining the physical mechanisms of subsonic flutter initiation in AGTE axial-flow compressor blade cascades. Such a combination of reduced frequencies and angles of attack is possible when the aerodynamic blade vibration decrement equals zero. It corresponds to the critical reduced vibration frequency value below which the aeroexcitation of blade vibrations and an increase in its level are observed, i.e., the dynamic subsonic cascade flutter loss is taking place. Known methods of evaluating these critical loss conditions are analyzed. The rapid method of predicting the dynamic subsonic flutter stability for compressor blade cascades is described. The scheme of critical reduced blade vibration frequency data base generation is tabulated as the critical values at fixed geometric cascade parameters (pitch-chord ratio and deflection angle), angles of attack, and coefficients of bending-torsional coupling. An example of such a data base for specific compressor blade cascades is given.

Dynamic modeling and flutter analysis of a fin-actuator system

Dynamic modeling and flutter analysis of a fin-actuator system

Stability of Differently Fixed Composite Cylindrical Shells Interacting with Fluid Flow

The problem of the stability of a fluid-conveying pipeline modeled by a composite orthotropic cylindrical shell of finite length with different boundary conditions at the ends is solved. The shell is subject to hydrodynamic pressure and uniform external static load. The effect of boundary conditions of the shell under external loading on the qualitatively different types of instability, quasistatic (divergence) and dynamic (flutter), that occur at certain “critical” velocities of the fluid is studied

Stability of Composite Cylindrical Shells with Added Mass Interacting with the Internal Fluid Flow

The effect of added masses on the quasistatic (divergence) and dynamic (flutter) loss of stability of cylindrical shells interacting with the internal fluid flow is studied. The dependence of the critical velocity of the fluid on the type of attachment of the added masses is analyzed

Aeroelastic benefits of tow steering for composite plates

The use of tow steered composites, where fibers follow prescribed curvilinear paths within a laminate, can improve upon existing capabilities related to aeroelastic tailoring of wing structures, though this tailoring method has received relatively little attention in the literature. This paper demonstrates the technique for a cantilevered flat plate in low-speed flow. A genetic algorithm is used to locate the Pareto front between static aeroelastic stresses and dynamic flutter boundaries. The impact of various tailoring choices upon the aeroelastic performance is quantified: curvilinear fiber steering versus straight fiber steering and certifiable versus non-certifiable stacking sequences.

Research on Transonic Wind Tunnel Flutter Test for a Wing Model

This paper adopts self-designed wing model to conduct flutter test on subsonic and transonic, and obtains flutter characteristic of the model, and the test results are used for calibration and verification of flutter procedures. The sub-critical extrapolation is used to obtain the flutter sub-critical parameters and the direct observation method is used to obtain comparison of results. Error of results obtained by the two approaches does not exceed 5%, and validates reliability of the sub-critical prediction approach in continuous adjusted dynamic pressure flutter test.

Research on Data Processing Method for Continuously-Varying Dynamic Pressure Flutter Test

For the continuously-varying dynamic pressure flutter test data in the high-speed wind tunnel; this paper analyzes the strengths and weaknesses of the data Processing Method in this field. The data selection and stacking mode is improved. A Butterworth IIR digital filter is used for digital filtering. The power spectral density function is computed by Fourier transform of the autocorrelation function. A pick-hold method is used to predict the flutter critical point. It is indicated that our method features high accuracy and efficiency by theoretical analysis and wind tunnel flutter test.

Aerothermoelastic topology optimization with flutter and buckling metrics

This work develops a framework for SIMP-based topology optimization of a metallic panel structure subjected to design-dependent aerodynamic, inertial, elastic, and thermal loads. Multi-physics eigenvalue-based design metrics such as thermal buckling and dynamic flutter are derived, along with their adjoint-based design derivatives. Locating the flutter point (Hopf-bifurcation) in a precise and efficient manner is a particular challenge, as is outfitting the optimization problem with sufficient constraints such that the critical flutter mode does not switch during the design process. Results are presented for flutter-optimal topologies of an unheated panel, thermal buckling-optimal topologies, and flutter-optimality of a heated panel (where the latter case presents a topological compromise between the former two). The effect of various constraint boundaries, temperature gradients, and (for the flutter of the heated panel) thermal load magnitude are assessed. Off-design flutter and thermal buckling boundaries are given as well.

Analysis of Dynamic Reliability on Large-Span Bridge

For the current study of large-span bridges are mostly in the component level, the real structural system reliability analysis is still relatively small, so based on the theory of dynamic reliability analysis of structure, the overall bridge structure system for the calculation model is established ,then reliability analysis under the multi-dimensional seismic load and the effect of dynamic flutter are performed, the results of sensitivity analysis with different parameters are obtained, so it is useful basis for the bridge design and evaluation.

MULTIBODY DYNAMIC MODELING AND FLUTTER ANALYSIS OF A FLEXIBLE SLENDER VEHICLE

In this paper, multibody dynamic modeling and flutter analysis of a flexible slender vehicle are investigated. The method is a comprehensive procedure based on the hybrid equations of motion in terms of quasi-coordinates. The equations consist of ordinary differential equations for the rigid body motions of the vehicle and partial differential equations for the elastic deformations of the flexible components of the vehicle. These equations are naturally nonlinear, but to avoid high nonlinearity of equations the elastic displacements are assumed to be small so that the equations of motion can be linearized. For the aeroelastic analysis a perturbation approach is used, by which the problem is divided into a nonlinear flight dynamics problem for quasi-rigid flight vehicle and a linear extended aeroelasticity problem for the elastic deformations and perturbations in the rigid body motions. In this manner, the trim values that are obtained from the first problem are used as an input to the second problem. The body of the vehicle is modeled with a uniform free–free beam and the aeroelastic forces are derived from the strip theory. The effect of some crucial geometric and physical parameters and the acting forces on the flutter speed and frequency of the vehicle are investigated.

STUDIES ON FLUTTER PREDICTION

The purpose of this paper is to study the instability of the dynamic flutter. The justification is expressed by the fact that the occurrence of flutter within the aircraft's flight envelope results in irreversible structural deformation which consequently leads to serious damage. Therefore the mathematical modeling of this phenomenon and its validation are very important. The instability of the dynamic flutter is characterized by critical speed and critical pulsation of oscillatory movements. In this paper, the quasi-stationary model and the Theodorsen model have been analyzed for calculating the aerodynamic forces and torques, and a comparison of them has been carried out. The fluid-structure coupling is done by rewriting the equations, considering that the forces are given by closed formulas. For the mathematical modeling of the flutter there have been used the p-k and V-g methods based on the Theodorsen model and the quasi-stationary model. In order to modeling the free vortices aerodynamic forces and moments, the equations which describe both the motion of the structure and the fluid flow had to be integrated simultaneously in time. The fluid-structure coupling is considered as a combination of two systems that describe the aeroelastic behavior of the structure.

Influence of initial deflections on the stability of composite cylindrical shells interacting with a fluid flow

Composite cylindrical shells interacting with an internal fluid flow are analyzed for stability. It is assumed that the shells have small initial geometrical imperfections. The effect of axisymmetric and nonaxisymmetric initial deflections on the critical speeds of the fluid, which cause static (divergent) or dynamic (flutter) loss of stability, is studied

Stability of cylindrical shells with added mass in fluid flow

The paper proposes a technique for the stability analysis of an elastic cylindrical shell with added mass interacting with a flowing fluid. Three cases of mass–shell contact are considered: the added mass (i) is attached to the shell at one point, (ii) has the form of a circular ring, and (iii) is distributed uniformly over the length. For each case, equations to determine the critical speeds of the fluid corresponding to the quasistatic (divergent) and dynamic (flutter) buckling of the shell are derived

Flutter and Thermal Deflection Suppression of Composite Plates Using Shape Memory Alloy

An efficient finite element method for predicting critical temperature, postbuckling deflection and flutter response is developed for composite plates embedded with prestrained shape memory alloy (SMA) fibers. The large panel deflection and the temperature-dependent material properties of SMA and composites are considered in the formulation. The finite element formulation and solution procedure of the incremental updated Lagrangian method for nonlinear temperature-dependent material properties are presented briefly. Flow yaw angle at supersonic speed is also considered. For the static solution, the system equations are solved by using the Newton-Raphson iteration method to determine aerothermal postbuckling deflection under the combined aerodynamic and thermal loads. For the dynamic flutter response, the modal method and time-domain numerical integration are employed. Results show that the critical buckling temperature can be raised high enough so that buckling deflection can be eliminated, and the desired flat and stable region in the temperature-dynamic pressure operating domain can be enlarged greatly for composite surface panels embedded with SMA for supersonic vehicle applications. Weight savings based on critical temperature when SMA is used are also presented.

Comparison of static and dynamic fluid-structure interaction solutions in the case of a highly flexible modern transport aircraft wing

This paper describes the computational work performed by five of the fifteen partners in the Brite-Euram project UNSI, for the prediction of static aeroelastic configurations and dynamic flutter response at transonic conditions, using advanced time-domain fluid-structure coupling methods. The aerodynamic models, mechanical models, and coupling strategies implemented in the different solvers are presented. A code to code validation of the fluid-structure coupled solvers has been achieved in the case of the highly flexible MDO wing. The coupled codes have each been used first for the computation of steady state flow and static deformations at different flight conditions. The investigation of flutter has been carried out for off-design, heavy-cruise flight conditions, using time-consistent numerical simulations. Dynamic responses have been recorded and compared for stable and flutter conditions.

Dynamic modeling of swept wing with PTFE method

A numerical approach for the solution of structural problems, based on the concept of parameter transfer finite elements, is here adopted to study the dynamic behaviour of composite wings. The purpose of this paper is to extend the methodology to a wing-like swept composite plate, which can be used, for example, for aeroelastic analysis, multidisciplinary optimization, structural control etc. The dynamics of composite swept wing is here analyzed and numerical results are compared with FEM solution. The effect of sweep angles and material anisotropicity on the aeroelastic behaviour of the wing is studied both from static divergency and dynamic flutter point of view. Several numerical results are presented.

DYNAMICS OF PRETWISTED ROTATING THIN-WALLED BEAMS OPERATING IN A TEMPERATURE ENVIRONMENT

The effects of a steady temperature gradient on eigenvibration characteristics of a rotating pretwisted thin-walled beam is addressed. The analysis is carried out in the framework of a refined theory of thin-walled anisotropic composite beams encompassing a number of nonclassical features. The displayed results reveal that the deterioration of material properties induced by the temperature rise yields a decay of eigenfrequencies and modification of natural modes, a fact that is likely to have detrimental repercussions upon their dynamic response and flutter instability characteristics. Moreover, as it was highlighted, the proper use of the tailoring technique can overcome the deleterious effect associated with the thermal degradation of material properties of blade structures.