Illinois scientists reduce jet noise by controlling turbulence

Washington, Sept 4 (ANI): Airlines and aircraft manufacturers are under increasing pressure to keep noise levels low for airport personnel and for people in surrounding neighbourhoods, but they are barely able to find any solution.

Now, scientists at the University of Illinois under a NASA-funded project are trying to reduce jet engine noise by controlling the unsteady movement of air, also known as turbulence, and they have developed a novel technique for the purpose.

Instead of working in a wind tunnel or laboratory, the team uses the Ranger supercomputer at the Texas Advanced Computing Centre to simulate the evolution of turbulence-generated sound waves from jet engine exhaust.

The simulations help explain how sound is generated on the most basic level, and also how it can be controlled using a new device.

"We're studying the controlled jet and the uncontrolled jet to understand what changes between them," Live science quoted Daniel Bodony, an assistant professor of aerospace engineering at The University of Illinois at Urbana-Champaign, as saying.

"That's what experiments can't currently do and what is missing from our understanding of the science," he stated.

After conducting four years of research, Bodony and his collaborators have developed a novel technique to determine the optimal controller required to reduce jet noise.

The controller is a plasma actuator based on those developed by colleagues at Ohio State - something like a giant spark plug - that alters the sound field by injecting heat.

The simulations on Ranger determined the ideal timing and strength of the perturbations to reduce the engine's radiated sound without significantly altering its thrust.

The first round of improvements showed the potential to reduce jet noise by three decibels, or the equivalent of 30 percent.

However, Bodony is confident that with further refinements, his group will be able to reduce the noise level even further.

Results of the group's theoretical and simulation work were published online in the Journal of Sound and Vibration in Feb. 2011. (ANI)