Aeroelastic Analysis Of High Aspect Ratio Wings

In this thesis,the static aeroelastic and flutter characteristics of high-aspect-ratio wings were analyzed considering the influences of large deformation.Firstly,torsion angles of two kinds of high-aspect-ratio wings with low sweep angles were calculated based on the classical lift-line theory by solving moment equilibrium equations.For the rectangular wing,which has constant spanwise structure parameters,the torsion angles under different flight conditions were obtained by solving the equilibrium equation directly.Otherwise,the torsion angles of trapezoidal wings with variable spanwise parameters were calculated by Galerkin method.The results can provide some suggestions for determining wing structure parameters.Secondly,the finite element model of a UAV wing in zero balance position was established according to the equivalence principle.The structure in non-zero balance position was obtained by loading ultimate flight load.The influences on structural dynamic characteristics due to large deformation were obtained through modal analyses in these two balance positions.The analysis results shed light on that the natural frequencies of the wing reduced and the coupling vibration mode appeared in advance.Finally,the flutter characteristics and divergence speed of the UAV wing were computed using MSC Nastran.The PK method was chosen to analyze the flutter characteristics of the wing in different sets of flight height and Mach.Ignoring the free-play in the aerodynamic model under zero balance position led the flutter velocity and frequency relatively small.By comparing the flutter analysis results in zero-balance and non-zero balance positions,it was found that the flutter velocities decreased due to structural deformation while the flutter modalities were almost constant.Moreover,the static aeroelastic divergence speed of the wing was calculated by flutter method based on the flutter analysis model.