Band gap and dispersion characteristics of phononic crystal microchannels under fluid solid coupling.

The fluid solid coupling effect in the flow microchannel system can easily induce severe vibration and noise, which seriously affects the performance and safety of the equipment. By its bandgap characteristics, the phononic crystal provides a new way to suppress the propagation of elastic waves in specific frequency bands. In this study, the vibration suppression of fluid-solid coupled phononic crystal microchannels under shock excitation is addressed. Compared with the inadequacy of the existing bandgap calculation methods in fluid computation, this study innovatively combines the transfer matrix method with the wave-finite element method to establish a fluid-solid coupled dynamics model and perform a systematic analysis. The significant effects of fluid filling on the bandgap characteristics are revealed: the unfilled microchannels show two bandgaps (70-90 Hz, 280-690 Hz) in 0-800 Hz; the bandgaps evolve to three (40-65 Hz, 180-340 Hz, 485-735 Hz) after fluid filling. At the same time, the transient vibration propagation and attenuation mechanisms of the system under different fluid shock excitations are deeply investigated. It is shown that the flow velocity is the key parameter affecting the shock vibration suppression effect: at 0 m/s flow velocity, the phonon crystal bandgap can effectively attenuate the shock response; as the flow velocity increases to 10 m/s, the fluid-solid coupling effect is enhanced, and the attenuation intensity is weakened. This study elucidates the quantitative relationship between key parameters such as flow velocity, structural periodicity, and resonant unit characteristics and shock vibration attenuation performance. It is expected to provide an important theoretical foundation and design basis for the design of flow microchannel systems with excellent shock resistance.