AUGUST 21, 2023 – The Office of Naval Research (ONR) sponsored a project at Virginia Tech University nearly 20 years ago that is now growing in influence across the world for measuring aerospace and aeronautical acoustics. Since noise reverberates against solid surfaces, such as the walls of a wind tunnel where acoustical testing takes place, collecting accurate sound data had been nearly impossible at the time. Researchers were also struggling to discern the sound of the wind tunnel’s air flow from the noise of the object traveling through it.
After learning about some experiments on Kevlar as a wind screen, William Devenport, an engineering professor and director of Virginia Tech’s Stability Wind Tunnel, said he and a colleague wrote a proposal to then-ONR program officer Ron Joslin to try adding Kevlar to their wind tunnel walls.
“The idea was that we would have the flow going on in the tunnel, the Kevlar would contain the flow and it would improve the aerodynamics. At the same time, the sound produced in the flow would be able to make its way out through the Kevlar, and we could hear it in the anechoic chamber,” said Devenport.
Devenport submitted the original grant proposal (N00014–04–1–04933) through the FY 2004 Defense University Research Instrumentation Program (DURIP) for alterations to Virginia Tech’s existing Stability Wind Tunnel that would allow it to measure flow-induced noise of relevance to Navy applications.
At the time, using Kevlar in a wind tunnel was such a novel idea that Joslin was warned by other Navy acoustic experts it would be a waste of resources. Now, as many as 20 major facilities around the world are using the technology to build a hybrid anechoic tunnel (HAWT) or upgrade their existing wind tunnels with Kevlar.
Dr. Julie Young, an ONR Sea Warfare and Weapons Department program officer for Power and Energy Research, National Naval Responsibility for Naval Engineering, gives credit to her predecessor, Joslin, for seeing the potential of this kind of research.
“It’s really nice to see a breakthrough idea that significantly advances the state of the art, the science in that area, and that’s why everybody else followed,” said Young.
Young oversees ONR’s propulsor hydrodynamics, hydroacoustics and structure dynamics portfolio, which includes the Kevlar wind tunnel program. In addition, Young said both she and Devenport are working with the North Atlantic Treaty Organization’s (NATO) advanced vehicle technology (AVT) program, which brings together experts related to air and water.
“I’m on three of the NATO AVT panels and one of them is led by William Devenport,” said Young. “In addition to lift, drag, thrust, stability – acoustics is also an important consideration.”
“This is relevant for aircraft and undersea craft, and by the way, it’s also relevant for a lot of energy harvesting devices like wind turbines because they also produce noise,” she continued. “We need to understand where the noise originates from and why and how it propagates.”
Devenport said acoustics are important for two reasons. “If we’re talking about aerospace or aeronautical applications – one is to control how loud things are inside the cabin. We’re working with Julie Young exactly on that subject – trying to measure the pressure fluctuations that cause vibrations in the aircraft that are heard inside.”
Devenport said the other reason to study acoustics is to learn how they affect the outside environment – the sound created by a hydroplane, for example, or the blades of a turbine.
In order to resolve an issue, Young said you have to understand the science behind it: “At ONR, the mission is foundational research that’s relevant to the Navy. We have to understand the science and by understanding, we develop technology.”
Although Devenport and his team at Virginia Tech have been working with Kevlar at their Stability Wind Tunnel for nearly two decades, he said they are still learning how well it works. But they are no longer flying solo. Wind tunnels adopting this technology include the Department of the Navy’s Anechoic Flow Facility at the Naval Surface Warfare Center Carderock Division, the JAXA 2M tunnel in Tokyo, the new Danish National Wind Tunnel, and the DSTG Low Speed Tunnel in Australia, as well as a number of universities in the U.S. and around the world.
Projects utilizing the technology have also spread to include the National Science Foundation, the National Renewable Energy Laboratory, National Aeronautics and Space Administration (NASA) and more than 70 commercially sponsored programs within large multinational companies.