Introduction to Aircraft Aeroelasticity and Loads

H

MATLAB/SIMULINK Programs for Flutter

In this appendix, some sample MATLAB programs are given for the calculation of the aeroelastic behaviour of a binary flutter system and also its response to control surface and gust/turbulence inputs.

H.1 DYNAMIC AEROELASTIC CALCULATIONS

In Chapter 11 the characteristics of the flutter phenomenon were described using a binary aeroelastic system. The following code sets up the system equations, including structural damping if required, and then solves the eigenvalue problem for a range of speeds and plots the V_ω and V_g trends.

% Flutter Chapter B04 Appendix
% Sets up the aeroelastic matrices for binary aeroelastic model, 
% performs eigenvalue solution at desired speeds and determines the frequencies
% and damping ratios
% plots V_omega and V_g trends
% and plots flutter conic solution
% Initialize variables
clear; clf
% System parameters
s = 7.5;          % semi span
c = 2;            % chord
m = 100;          % unit mass / area of wing
kappa_freq = 5;   % flapping freq in Hz
theta_freq = 10;  % pitch freq in Hz
xcm = 0.5*c;      % position of centre of mass from nose
xf = 0.48*c;      % position of flexural axis from nose
e = xf/c - 0.25;  % eccentricity between flexural axis and aero centre (1/4 chord)
velstart = 1;     % lowest velocity
velend = 180;     % maximum velocity
velinc =0.1;      % velocity increment
a = 2*pi; % 2D lift curve slope rho = 1.225; % air density Mthetadot = -1.2; % unsteady aero damping term M = (m*c^2 - 2*m*c*xcm)/(2*xcm); % leading edge mass term damping_Y_N = 1; % ...