Theoretical And Experimental Study On Aeroelastic Stability Of Subsonic Plates With Different Boundary Conditions

In this thesis,the aeroelastic stability of plate with two-dimensional panels in subsonic flow with different boundary conditions is theoretically and experimentally investigated.Plates with various types of boundary conditions are considered,and they are plates with fixed ends(simply supported or clamped at both ends),the conventional cantilever plates(with the plate leading edge fixed and free at another)and the inverted cantilever plates(with the plate trailing edge fixed and free at another).The main contents of this paper are as follows:1.The background and significance of the research in this paper is detailed presented.Based on summarizing the existing research results,the present theories of plate aeroelastic problems and the shortcomings are pointed out.In addition,it is shown that the related studies about the panels with different boundary conditions,in cavity effect,and in imperfect factors of fluid are still limited.2.The aeroelastic instability of plates with both ends fixed in cavity effect is analyzed by using potential flow theory.Firstly,considering the wall effect of the cavity,the aerodynamic pressure on the upper and lower surfaces of the plate are obtained by the thin airfoil theory and the method of images;secondly,the Galerkin method is used for the analysis of the instability boundary.It is founded that increasing of the axial force and the support stiffness of plates can effectively increase critical velocity;a fast method for the critical instability mode of the system under different axial force,support stiffness and bending stiffness is suggested.Based on the theoretical calculation of the simply supported plates,it is shown that the difference between single-mode calculation and the mode-coupling calculation for the instability is not obvious.3.In view of the influence of many imperfect factors in fluids,the influence of fluid viscosity and turbulence is considered in the modeling of plates in cavity effect.It is shown that the viscosity of the fluid is large at low Reynolds number(R_e),which has a strong stabilizing effect on the plate by increasing the critical dynamic pressure,and the viscosity effect can be ignored if R_e>>2000.The turbulence coefficient of an ideal laminar state is C_P=1,?=0,and the instability dynamic pressure increase with the increase of?when C_P is constant,but decrease with the increase of C_P when?is constant.4.The flutter boundary of a conventional cantilever plate by considering the viscous tension is obtained by using a traveling wave solution,and the flutter characteristics of the conventional cantilever plate are studied by wind tunnel experiment.It is found that the clamping,material characteristics(internal damping,etc.)and machining accuracy are the key factors for the experimental accuracy;the traveling wave solution of k=1.6?has a good accuracy compared with the experiment.The other existing theories of two-dimensional and three-dimensional are ideal for the cantilever plate with small size and small aspect ratio,but they have not good accuracy for plate with large three-dimensional deformation.The hysteretic phenomenon of flutter critical velocity in a cantilever plate is founded.5.Based on the lifting-line theory,the critical instability velocity of an inverted cantilever panel without wall is theoretical calculated.When the wall effect is considered,an equivalent test method is designed and the wind tunnel experiment is completed.The experimental results show good agreement with the theoretical results from lifting-line theory and other numerical solutions,which in turn show the accuracy of the present studies.The effect of the rigid wall rapidly decreases with the increase of the distance between the wall and the panel,when the distance is larger than the plate length,the effect of the wall can be reasonably ignored.