Hypersonic flutter analysis based on three-dimensional local piston theory

ifasd2024 Tracking Number 92

Hypersonic vehicles have become a research hotspot these years. This kind of aircraft often has a slender body layout using a thin-walled structure and lightweight materials, which causes special and significant aeroelastic flutter problems. In this research, a hypersonic flutter analysis method based on three-dimensional local piston theory(3D-LPT) is developed and verified with wind tunnel test results. Using a local coordinate system of wall surface, local piston theory can be extended to 3D. Combined with Euler-CFD calculation, a high-precision three-dimensional discrete hypersonic unsteady aerodynamic force model is established in the body axis system Oxyz: where is the outward normal unit vector of a wall surface element and denotes the displacements of the element. , and are the projections of surface local flow velocity in the x, y, and z directions. and are the local density and sound speed, respectively. These local flow parameters are determined by CFD calculation. The generalized aerodynamic force can be expressed explicitly in the time domain as a combination of generalized aerodynamic influence coefficient (AIC) matrix A and generalized coordinate q in the small-disturbance range around a specific flow state. Therefore, an aerodynamic-structure tight coupling aeroelastic flutter equation can be established in the state-space form: where and are the generalized mass matrix and generalized stiffness matrix, respectively. Based on this state-space form flutter equation, Lyapunov's first method can be used to analyze the flutter stability of the aeroelastic system. As shown in the figure below, a supersonic fin model with wind tunnel test results is used to verify the accuracy of the proposed method. Comparing the numerical results calculated by the 3D-LPT-based method with wind tunnel test results, the numerical errors of flutter speeds at all AOA cases are less than 11%. This 3D-LPT-based hypersonic flutter analysis method can analyze 3D complex objects while suitable for conditions with high AOA or wide Mach number range. Combined with CFD calculation, aerodynamic nonlinear effects can be considered. Based on the aerodynamic-structure tight coupling model, the proposed method has high accuracy and efficiency. By comparing with wind tunnel data, the effectiveness of the proposed method is proved.