Keywords: aeroelasticite ; structure : dynamique Reference Record created on 2005-11-18, modified on 2016-08-08

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Introduction to Structural Dynamics and Aeroelasticity

A new finite state aerodynamic theory is presented for incompressible, two-dimensional flow around thin airfoils. The theory is derived directly from potential flow theory with no assumptions on the time history of airfoil motions. The aerodynamic states are the coefficients of a set of induced-flow expansions. As a result, the finite state equations are hierarchical in nature and have closed-form coefficients. Therefore, the model can be taken to as many states as are dictated by the spatial texture and frequency range of interest with no intermediate numerical analysis. The set of first-order state equations is easily coupled with structure and control equations and can be exercised in the frequency or Laplace domain as well as in the time domain. Comparisons are given with Theodorsen theory, Wagner theory, and other methods. Excellent results are found with only a few states.

Finite state induced flow models. I - Two-dimensional thin airfoil

Application of a three-field nonlinear fluid–structure formulation to the prediction of the aeroelastic parameters of an F-16 fighter

An integrated computational fluid dynamics (CFD) and computational structural dynamics (CSD) method is developed for the simulation and prediction of flutter. The CFD solver is based on an unsteady, parallel, multiblock, multigrid finite volume algorithm for the Euler/Navier-Stokes equations. The CSD solver is based on the time integration of modal dynamic equations extracted from full finite element analysis. A general multiblock deformation grid method is used to generate dynamically moving grids for the unsteady flow solver. The solutions of the flowfield and the structural dynamics are coupled strongly in time by a fully implicit method. The coupled CFD-CSD method simulates the aeroelastic system directly on the time domain to determine the stability of the aeroelastic system. The unsteady solver with the moving grid algorithm is also used to calculate the harmonic and/or indicial responses of an aeroelastic system, in an uncoupled manner, without solving the structural equations. Flutter boundary is then determined by solving the flutter equation on the frequency domain with the indicial responses as input. Computations are performed for a two-dimensional wing aeroelastic model and the three-dimensional AGARD 445.6 wing. Flutter boundary predictions by both the coupled CFD-CSD method and the indicial method are presented and compared with experimental data for the AGARD 445.6 wing.

Calculation of Wing Flutter by a Coupled Fluid-Structure Method

An overview is given of recent advances in a three-field methodology for modeling and solving nonlinear fluid-structure interaction problems, and its application to the prediction of the aeroelastic frequencies and damping coefficients of a full F-16 configuration in various subsonic, transonic, and supersonic airstreams is reported. In this three-field methodology the flow is described by the arbitrary Lagrangian-Eulerian form of the Euler equations, the structure is represented by a detailed finite element model, and the fluid mesh is unstructured, dynamic, and updated by a robust torsional spring analogy method. Simulation results are presented for stabilized, accelerated, low-g, and high-g flight conditions, and correlated with flight-test data. Consequently, the practical feasibility and potential of the described computational-fluid-dynamics-based computational method for the flutter analysis of high-performance aircraft, particularly in the transonic regime, are discussed.

Aeroelastic Dynamic Analysis of a Full F-16 Configuration for Various Flight Conditions

The difference between a true damping, or rate-of-decay, solution of the flutter equation and the structural-damping-type of solution is highlighted. True damping solutions are possible if unsteady aerodynamics can be expressed in terms of the complex variable p. If the aerodynamics are given at discrete values of the reduced frequency fc, an approximate determination of the true damping is possible by assuming that the aerodynamic forces for harmonic motion are a good approximation for the cases of slowly increasing or decreasing amplitude. A determinant iteration method for obtaining the solution is presented. Results obtained by different methods of solving the flutter equation are compared.

Hermann J. Hassig

Papers

An Approximate True Damping Solution of the Flutter Equation by Determinant Iteration