An experimental investigation of some effects of spanwise location of one, engine-pod like, concentrated mass on transonic flutter characteristics of thin cantilever wings having a sweptback angle of quarter chord line of 20° and panel aspect ratio and taper ratio of 4.0 and 0.4, respectively, has been conducted in the N.A.L. 60cm×60cm transonic blowdown wind tunnel for fiutter testing at Mach numbers between 0.759 and 0.963. The experimental results are presented in comparing the boundary of fiutter density and egperimental flutter-velocity coefficient of the respective wing-pod configuration experimented, as a function of Mach number, and also are compared with the calculated results by the matrix iteration method employing two-dimensional incompressible unsteady flow theory as required oscillatory aerodynamic forces.
The nonlinear theoretical analysis of supersonic panel flutter of circular cylindrical shells is performed in order to compare with the authors' experimental results, which could not be explained by the linear analysis. The nonlinear governing equation is solved approximately with the aid of the methods of averaging and numerical integration. The method of averaging is used in order to obtain the solutions of the steady-state vibration and examine its stability for small disturbances. The results of the numerical integratio n indicate that the calculated values of amplitudes, frequency and phase difference for the circumferential wave number which was observed in the experiment agree well with those obtained from the experiment. They also indicate that the flutter occurs for finite disturbances in a certain region below the minimum value of the critical dynamic pressure predicted by the linear theory. The nonlinear theoretical analysis provides a good explanation for the experimental results both qualitatively and quantitatively.
A method to calculate the supersonic bendingtorsion flutter speed of cantilever plate wings of low aspect ratio is presented. The deflection mode is assumed in a double power series expansion of spanwise and chordwise variables, and the flutter determinant is derived with the aid of the principle of minimum potential energy of the dynamic problem. The chordwise variable is measured from the midchord line along the stream direction for swept-back wings. For the aerodynamic force, the piston theory including the effect of wing thickness is used. Numerical computation is carried out for a cantilever trapezoid tested at the National Aerospace Laboratory. It has been observed that the ten terms approximation yields a good result in comparison with the twenty terms approximation. It has been clarified that the effect of aerodynamic damping on the flutter speed is very small. Reasonable results are obtained in comparison with the experimental results. Furthermore the present method is extended to cantilever plates partially clamped at the root.