Hypersonic flight has transformative potential across commercial aviation, defense, and space exploration. However, extreme velocities, temperatures, and pressure loads pose significant technical challenges. One critical issue is the interaction of shock waves with boundary layers (SWBLIs), which exacerbate turbulence, increase heat transfer and drag, and destabilize vehicle structures. Traditional flow control methods—active, interactive, and passive—have shown limited effectiveness under the extreme conditions of hypersonic flight, necessitating novel approaches.
This study explores the use of phononic metamaterials (PMs) for passive flow control in hypersonic SWBLIs. We designed, analyzed, fabricated, and tested a PM targeting the low-frequency disturbances (<1 kHz) prevalent in SWBLIs. The test configuration involved a semi-infinite cylinder mounted on a rigid wall subjected to Mach 7.2 flow in a Ludwieg tube. The PM was constructed using aluminum and silicone layers and optimized for a bandgap between 364 Hz and 900 Hz, confirmed through finite element simulations and frequency response analysis.
Experimental tests compared two scenarios: a reference case with a rigid wall and a test case incorporating the PM as a subsurface. Schlieren imaging revealed that the PM reduced the strength of the shock waves, suggesting effective attenuation of upstream disturbances. The AM subsurface minimized impedance mismatch and was robustly integrated into the test setup.
Preliminary results demonstrate the PM’s potential in mitigating flow instabilities and turbulence in hypersonic conditions. These findings highlight the transformative role of phononic metamaterials in improving the safety, performance, and efficiency of hypersonic vehicles by reducing drag, heat transfer, and mechanical stresses.
