New subsurface material calms jet turbulence with microscopic vibrations at 640 mph

A new study proposes a material-based approach to reduce aerodynamic drag and turbulence on air vehicles. Researchers behind the study from the University of Colorado Boulder state that the findings could help in major fuel savings for commercial airlines and high-speed aircraft. With a 2023 study showing severe turbulence has jumped up to 55% since 1979 due to climate change, this technology arrives at a crucial moment. Cutting down the fuel usage Ever since the dawn of flight, making a plane faster and cleaner meant reinventing its silhouette or changing its shape. But the new study suggests that it is not entirely the case, and there are other new ways also. In this work, aerospace engineers are instead modifying the material under the aircraft’s skin to neutralize turbulence at the source before it ever rattles the wing. The key is using synthetic, subsurface materials to generate microscopic vibrations that stop turbulence in its tracks and slash aerodynamic drag. Visualization of super resonance on a coiled phononic structure. Credit: Hussein et al./ CU Boulder At 640 mph, air pummels an aircraft’s surface to create a turbulent boundary layer that acts like an invisible anchor, forcing engines to burn more fuel. This new technology could dampen chaotic friction to cut carbon emissions and save commercial airlines billions of dollars on flights that consume over 10,000 gallons of fuel per cross-country trip. “The prevailing paradigm since the beginning of aviation is to control drag by only shaping the vehicle,” said Mahmoud I. Hussein, professor of aerospace engineering at CU Boulder. “Now we have a new concept to influence surface drag using materials that can dynamically interact with the airflow, enhancing the vehicle performance in an unprecedented manner,” the lead researcher added. Decade-long work Basically, researchers are looking to phonons, which are tiny, subatomic-scale vibrations trapped inside the physical structure of a material. Hussein started working on the concept of “phononic subsurfaces” (PSubs) a decade ago. These tiny subsurface structures absorb energy from passing wind and flex ever so slightly, sending out-of-phase vibrations back to the surface. The resulting microscopic ripple smooths the flow passively without heavy motors or complex moving parts. Early phononic subsurface prototypes were limited to targeting a single, precise vibration frequency, making them ineffective against the chaotic spectrum of real-world turbulence. In two papers published in Physical Review X and Proceedings of the Royal Society A, the team resolved these legacy issues by introducing super-resonance and scatterless interference. Super-resonance is achieved by coiling subsurface structures to absorb vibrations across a broad frequency band. Scatterless interference uses strategic grid arrangements to suppress turbulence across large downstream surfaces like wings and fuselages. “Scatterless interference gives us a way to attenuate the spatial behavior of the instability field downstream of the PSub, while super-resonance gives us a way to broaden the range of frequencies over which the control can operate,” explained PhD student Adam Harris. “Together, they bring the original PSub concept closer to the level of versatility needed for real-world flow environments,” the co-author noted. Concept-level only Although the research is currently focused on computer simulations, phononic subsurfaces are rapidly moving beyond theory. Global research groups have already constructed physical prototypes and are preparing wind-tunnel experiments to demonstrate their real-world effectiveness. The super-resonance and scatterless interference concepts could have far broader reach apart from aviation. According to researchers, the tech can optimize efficiency across marine hulls, commercial pipelines, and turbomachinery. Get the latest in engineering, tech, space & science - delivered daily to your inbox.Mrigakshi is a science journalist who enjoys writing about space exploration, biology, and technological innovations. Her work has been featured in well-known publications including Nature India, Supercluster, The Weather Channel and Astronomy magazine. If you have pitches in mind, please do not hesitate to email her.