Engine treatment could reduce jet noise

There’s one song that anyone who lives near an airport or directly under the flight path of arriving and departing jets wishes they could play: Simon and Garfunkel’s “The Sound of Silence.”

How bad is airplane noise? In a 2022 report, scientists from New Jersey—which, as the most congested state in the U.S., know a thing or two about noise—said that residents living in noise-polluted areas, such as airports, have a higher risk of heart disease. The seizure rate is 72% higher. Quiet area. Abel Moreira, a professor at Rutgers Robert Wood Johnson Medical School, said noise pollution should be considered responsible for heart disease.

In London, the Aviation Environmental Federation recently declared, “Aircraft noise can affect memory and learning in children, disrupt sleep, and cause long-term health problems.”

A Belgian environmental group estimated that the total health costs for residents suffering from airport noise exceeded 1 billion euros (1.07 billion in US dollars). They calculated that 51,000 people are at increased risk of developing high blood pressure and 2,000 are at increased risk of heart disease due to sleep disruption and constant daytime noise from airports.

The European Union has issued a directive banning excessively noisy airlines from flying in European airspace.

Belgium began taking action to curb jet noise in April as it introduced a tax on short-haul flights and private jets.

And BWI Airport in Baltimore has begun a $35 million multi-year project to install soundproofing for more than 400 homes surrounding the busy—and notoriously noisy—terminal.

Now there is welcome news from the University of Shanghai amid growing concerns about the harmful effects of noise. A team of researchers has developed a model that Interesting Engineering has called “a groundbreaking” advance that will rapidly stop the ear-splitting noise of jet engines.

In their paper, “Noise Control for High Subsonic Jet Flow by Inner Wall Treatment,” published in May advances in aerodynamicsThe researchers detailed several simulations carried out in air turbulence, air acoustics and hydrodynamics.

They relied on classic works such as the Ffowcs Williams–Hawkings equation, which was widely used to assess sounds generated by aircraft propellers, helicopter rotors and turbo machinery. John F. Fox Williams is best known for his contributions to the design of the supersonic Concorde jet.

The Shanghai team investigated issues such as shear layer instability, flow fields and far-field noise.

They came up with a jet engine treatment called the Wavy Inner Wall (WIW), in which they replaced the smooth inner wall at the exit of the nozzle with wavy patterned walls. A nozzle is a specially shaped tube that contains hot gases that generate thrust.

The concept, first proposed by MIT researchers in 2019, “enables fine-scale turbulence to be controlled”, according to Huyu Mao, one of the Shanghai researchers.

The result is “a reduction in mid- to high-frequency noise,” Mao said.

The Shanghai WIW solution improves on earlier efforts by others that hindered engine thrust or required additional equipment to meet noise and thrust objectives.

The Shanghai treatment provides low thrust loss and does not depend on other structures to achieve significant noise reduction.

“The wavy wall control method induces very small geometric modifications, which introduce an insignificant sacrifice in thrust while enhancing shear layer mixing,” Mao said. “Consequently, the wavy wall is a promising method for flow and noise control for subsonic jets.”

Very soon, as the concept is further refined and eventually brought into production, we may be able to join Simon and Garfunkel, the pop duo who performed at one of the world’s busiest airports (in Queens, New York). JFK) to a refreshingly peaceful rendition of “The Sound of Silence” elevated in minutes.

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