Three-dimensional fluid-structure-acoustic method for aeroelastic flutter analysis of coupled composite panel and cavity system in supersonic flow

The paper develops a partitioned three-dimensional fluid-structure-acoustic method to predict the flutter behaviors of a composite panel with a cavity beneath it in supersonic airflow. A higher-order shear deformation theory is employed for laminated panel modeling, considering zigzag effect, and panel’s large deformation is accounted for by incorporating nonlinear von Kármán strains. The supersonic airflow is formulated by the unsteady Navier-Stokes equations within the arbitrary Lagrangian-Eulerian framework, which are solved by a finite volume method. Additionally, the sound waves considering finite-amplitude effects, are calculated using a nonlinear finite element method. An implicit partitioned coupling method is used to establish the strong coupling between the unsteady supersonic airflow, composite panel with large deformation, and nonlinear sound waves, which is confirmed through a monolithic fluid-structure-acoustic coupling method. It is revealed that the composite panel-cavity aeroelastic system exhibits a special flutter induced by acoustic resonance, underscoring the crucial role of acoustic-elastic coupling in nonlinear aeroelastic responses. The impact of instability coefficients on flutter dynamics, as derived from linear modal analysis, is discussed, emphasizing that long-time scales are required for the establishment of acoustic resonance within the cavity. The findings suggest that flutter induced by acoustic resonance leads to an acoustic environment with high sound pressure levels in the cavity, particularly in shallow cavities, which could potentially cause detrimental acoustic fatigue of the structure.