Buzz Characteristics Under Fluid-Structure Interaction of Variable-Geometry Lip for Hypersonic Inlet

Variable-geometry lip structures can effectively broaden the operating range and improve the performance of hypersonic inlets. However, the presence of connection devices leads to a significant reduction in structural stiffness, which can easily trigger fluid-structure interaction (FSI) issues of the lip. In this study, an in-house FSI program is employed to investigate the buzz characteristics under FSI of the lip for a hypersonic inlet. The results indicate that FSI induces instability in the downstream shock train, resulting in the premature occurrence of inlet buzz. The buzz mode induced by FSI significantly differs from the rigid inlet buzz. During the buzz induced by FSI, both violent and mild buzz modes coexist, with these two modes irregularly alternating. During the violent buzz, the inlet achieves a brief start, leading to a fundamentally different evolution of the flowfield structure compared to the rigid model. During the mild buzz, the inlet remains unstart, so the evolution of the flowfield structure is similar to that of the rigid model. In comparison to the rigid inlet buzz, the amplitudes of pressure fluctuations significantly increase, and the dominant frequency decreases for the buzz induced by FSI. Simultaneously, different evolution characteristics of flow frequencies within various inlet regions are observed. Additionally, performance parameters no longer exhibit regular cyclic variations, with significant amplifications in their amplitudes. This study deepens the understanding of the buzz characteristics under FSI of lips for hypersonic inlets and provides a novel perspective on the mechanisms underlying buzz occurrence.