NONLINEAR BEHAVIOR OF A TYPICAL AIRFOIL SECTION WITH CONTROL SURFACE FREEPLAY - A NUMERICAL AND EXPERIMENTAL-STUDY

A three degree-of-freedom aeroelastic typical section with control sur face freeplay is modeled theoretically as a system of piecewise linear state-space models. The system response is determined by time marchin g of the governing equations using a standard Runge-Kutta algorithm in conjunction with Henon's method for integrating a system of equations to a prescribed surface of phase space section. Henon's method is use d to locate the ''switching points'' accurately and efficiently as the system moves from one linear region into another. An experimental mod el which closely approximates the three degree-of-freedom typical sect ion in two-dimensional, incompressible flow has been created to valida te the theoretical model. Consideration is given to modeling realistic ally the structural damping present in the experimental system. The ef fect of the freeplay on the system response is examined numerically an d experimentally. The development of the state-space model offers a lo w-order, computationally efficient means of modeling fully the freepla y nonlinearity and may offer advantages in future research which will investigate the effects of freeplay on the control of flutter in the t ypical section. (C) 1997 Academic Press Limited.