New phononic subsurface designs could help control aircraft turbulence more broadly and predictably without reshaping the vehicle.
At cruising speed, a passenger jet can travel around 640 mph while its wings push through turbulent air along their surfaces. That boundary layer turbulence can increase drag, making flight less efficient and requiring more fuel.
Mahmoud I. Hussein is exploring a different way to control that airflow. Rather than changing the external shape of an aircraft, his research uses engineered microscopic vibrations generated by synthetic materials beneath the surface, with the goal of reducing turbulence and improving fuel efficiency.
That potential matters because a commercial aircraft can burn more than 10,000 gallons of jet fuel during a single cross-country flight. Even modest gains in efficiency could therefore translate into substantial savings for airlines.
In papers published in Physical Review X and Proceedings of the Royal Society A, Hussein and his colleagues describe two advances that move the concept closer to practical use: super resonance and scatterless interference.
“The prevailing paradigm since the beginning of aviation is to control drag by only shaping the vehicle. 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,” said Hussein, a professor in the Ann and H.J. Smead Department of Aerospace Engineering Sciences at the University of Colorado Boulder.
Hussein also holds a courtesy appointment in the Department of Physics and is affiliated with the Materials Science and Engineering Program.
Tiny vibrations could reshape airflow control
At the center of his work are phonons, tiny vibrations that occur within a material rather than through the motion of an entire structure. The movements themselves are extremely small, but controlling them can influence how a surface interacts with flowing air.
The study of these internal vibrations forms the basis of phononics, a field Hussein has helped develop for more than two decades. In 2011, he helped establish the Phononics 20xx conference series, which has become a major international meeting for researchers in the field.
In 2015, Hussein introduced phononic subsurfaces (PSubs), engineered materials placed below a surface that can passively control vibrations where that surface meets a flowing fluid. Designs created by his group and other researchers have traditionally operated at only one frequency.
Two advances address major limitations
Hussein has now shown that coiling PSubs can extend their effects across a range of frequencies. The resulting phenomenon, called super resonance, addresses one of the major limitations of earlier designs by allowing the structures to interact with the broader range of frequencies found in real turbulence.
“We started with one frequency and aspired to eventually cover a broad range of frequencies, which is the way turbulence is generated in the real world. Now we’re there. A coiled phononic structure overcomes a long-standing limitation in laminar flow control strategies,” Hussein said.
Scatterless interference tackles a different problem. Instead of placing one PSub at a single location, researchers can arrange multiple PSubs in a grid or lattice so their effects extend downstream across a larger surface, such as an aircraft wing or the body of a hypersonic vehicle.
“This allows effective downstream control,” Hussein said. “These two problems, downstream control and broadband control, have been the key limitations of the technology since its introduction over a decade ago. We’ve resolved both.”
Adam Harris, a materials science and engineering PhD student in Hussein’s lab and coauthor on both papers, said the two developments complement each other.
“These two new milestones provide complementary solutions toward the puzzle that is the effectiveness of PSubs for actual flight conditions,” Harris said. “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. Together, they bring the original PSub concept closer to the level of versatility needed for real-world flow environments.”
Real-world testing is the next step
The current results are computational, but PSubs are no longer purely theoretical. Research groups around the world have already constructed working physical prototypes and are moving toward tests in wind tunnels.
“Our goal is to move beyond the traditional paradigm that flow control must come from solely changing the shape of the exposed surface or, more recently, using active actuators,” Hussein said. “With phononic subsurfaces, a wing or a fuselage can retain its shape and smoothness and remain passive, while the material beneath it is engineered to allow interaction with the flow in a highly targeted way.”
Although the work currently centers on aerospace applications, super resonance and scatterless interference could have uses well beyond aircraft.
“In addition to aircraft, this could be important for marine vessels, pipelines, turbomachinery, anywhere turbulence is an issue. In fact, both ideas may have application beyond flow control altogether,” Hussein said.
Reference: “Super-resonance: Breaking the Bandwidth Limit of Resonant Modes and Its Application to Flow Control” by Adam R. Harris, Armin Kianfar, David Roca, Daniel Yago, Christoph Brehm and Mahmoud I. Hussein, 28 May 2026, Physical Review X.
DOI: 10.1103/766t-tqsy
The ongoing research also tackles hypersonic flows and is supported by a $7.5 million, five-year Department of Defense Office of Naval Research (ONR) Multidisciplinary University Research Initiative (MURI).
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.