Broadband flow control through super resonance in a coiled phononic subsurface

Phonon motion beneath a surface interacting with a flow can be engineered to attenuate flow instabilities and delay laminar-to-turbulent transition. This principle underlies the concept of phononic subsurfaces (PSubs)—synthesized elastic structures embedded underneath a flow-facing surface and configured to extend upward such that their top face directly couples to the fluid. A PSub enables control through resonant or anti-resonant interferences, concepts rooted in crystal physics, by tuning subsurface phonon dynamics to modulate perturbation energy in the adjacent flow. Conventional PSubs, however, rely on conventional  resonant behavior and are therefore limited in bandwidth. We introduce super resonance, a new regime of resonant behavior that fundamentally extends the spectral reach of the PSub approach. In this regime, a mode’s out-of-phase response persists far beyond its natural bandwidth, enabling broadband dynamic interaction with the flow. This behavior is realized in a coiled PSub architecture—a locally resonant elastic metamaterial designed to admit multiple internal energy pathways that converge at a single structural location. The resulting response maintains an out-of-phase behavior across a frequency range far exceeding that of a conventional resonance. Direct numerical simulations confirm that a super-resonant PSub can passively suppress four unstable perturbation modes simultaneously in a channel flow, spanning a frequency band more than five times wider than that achievable with a corresponding uncoiled configuration. By enabling broadband flow stabilization, super resonance overcomes a fundamental limitation of existing passive control strategies and establishes a framework for tackling the more complex challenge of turbulent-flow control.