关键词: 超声速进气道, 激波边界层干扰, 肩部分离泡, 三维效应, 流-声模态, 谱本征正交分解

Abstract: The separation bubble induced by shock wave/boundary layer interaction (SWBLI) near the shoulder of a supersonic inlet is a critical issue affecting inlet stability and aerodynamic performance. Wind tunnel experiments were conducted to systematically investigate the three-dimensional effects, unsteady loads, and dominant hydrodynamic-acoustic modal characteristics inside the shoulder separation bubble of a two-dimensional rectangular inlet at Mach numbers Ma=3.0~4.0. High-frequency fluctuating pressure sensors, high-speed schlieren imaging, and a hydrodynamic-acoustic separation technique based on micro-perforated panels were employed to synchronously acquire wall-pressure-field and flow-structure data. The results show that, with increasing Ma, the streamwise scale of the separation bubble increases while its three-dimensional effects weaken, and the reattachment point oscillation region moves downstream. At Ma=4.0, the oscillation range reaches 1.3H (x/H=11.3~12.6). The spatial power spectra and sound pressure level distributions indicate that the separation point and reattachment region of the separation bubble are the primary unsteady source regions in the flow field. The dominant hydrodynamic/acoustic modes in the pressure loads, namely turbulent convection and acoustic wave propagation, were effectively identified using acoustic measurement points, revealing different dominant physical mechanisms in the low- and high-frequency ranges. Spectral proper orthogonal decomposition (SPOD) based on high-speed schlieren sequences was used to extract coherent spatial modes at multiple frequencies, demonstrating that the flow is dominated by the superposition of multi-frequency coherent structures.

Key words: supersonic inlet, shock wave/boundary layer interaction, shoulder separation bubble, three-dimensional effect, hydrodynamic-acoustic mode, spectral proper orthogonal decomposition