Effects of sound field on thin-wall cylindrical structure dynamic characteristics

The acoustic-structure coupling problem is much concerned in the running process of the aerospace vehicle. Aiming at a representative thin wall cylindrical structure, a 3-D dynamic model of acoustic-structure direct coupling is built. The modeling involves solid finite elements for the structure and 3-D acoustic elements for the sound field, and the infinite elements are employed in describing the free boundary conditions. The vibration characteristics of the light fluid-thin wall cylindrical structure, such as modal, amplitude and phase frequency response, are investigated through theoretical and numerical analyses. The effects of acoustic vibration on the structural dynamic characteristics and the corresponding mechanism are discussed. It is found that the natural frequencies of the structure are decreased in most cases due to the effects of sound field. In low frequency stage, the structure is added with some mass due to the acoustic vibration. But, the effects of acoustic vibration are similar to the effects of damping in high frequency stage. With the rise of fluid density, most natural frequencies decrease remarkably. The amplitudes of structural response increase in low frequency stage and decrease in high frequency stage. The sound velocity has remarkable influence on sound field mode, but has little influence on structural mode frequencies.