Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Fighting sound with sound, new modeling technique could quiet aircraft

24.02.2006


Newly published research by a Princeton engineer suggests that understanding how air travels across the sunroof of a car may one day make jet engines less noisy.



Clarence Rowley, an assistant professor of mechanical and aerospace engineering, did not actually conduct his experiments on a sunroof. Rather, he and collaborators used computer simulations and subsonic wind tunnels at Princeton and at the U.S. Air Force Academy in Colorado Springs, to experiment with models that resembled the open sunroof of a speeding car.

Rowley showed that his simulations could predict how sunroof air flow would behave under various conditions. Just as important, he figured out how to negate the noise that it produced. Rowley’s findings are published in the January issues of the Annual Reviews of Fluid Mechanics and the Journal of Fluid Mechanics.


This research may ultimately lead to modifications of jet engines to make them quieter as they fly over neighborhoods. The research also has important military applications. For example, it would enable stealth aircraft to fly faster because it would reduce buffeting when doors of a weapons bay are open. And Rowley is currently using insights garnered from this work to help develop ultrasmall, unmanned aircraft that would be useful for surveillance or search-and-rescue missions.

Rowley’s task was not an easy one. To precisely model the air current would have required solving more than 2 million equations. Solving these equations by themselves is not too great a challenge for today’s computers, but manipulating them to figure out how to make the air flow quieter would require far more calculation.

"Basically, it would have been computationally impossible," Rowley said.

So he took an unusual approach. He selectively picked mathematical tools from three different disciplines – dynamical systems, control theory and fluid mechanics – and yoked them together to come up with a computer simulation that, by solving only four equations, could approximate almost identically the answer to the problem that normally would have taken 2 million equations to figure out.

Once he figured out the model, Rowley fought sound with sound.

Rowley focused on the layer of air just above his simulated sunroof, where faster moving air "shears" away from slower moving air. "This shear layer flaps and up and down like a flag in the wind," Rowley said.

Each time this layer of air flaps down and hits the leading edge of the sunroof, it makes what scientists call an acoustic wave (most people just call this noise).

In his computer model and in wind-tunnel experiments with collaborator David Williams of the Illinois Institute of Technology, Rowley placed a speaker at the front end of his sunroof and a microphone at the rear of the roof. The microphone monitored the flapping and fed this information to a controller. The controller, relying on predictions from Rowley’s model, then sent an opposing signal to the speaker, which is not much different than one found on a typical stereo.

"The physical mechanism is actually very simple," Rowley said. "When the flag wants to push up we pull it down; when it wants to pull up we push it down. This is what makes it quiet."

The same principles can be applied to quiet down a jet engine or silence the open bays of a military craft. Rowley does not have immediate plans to promote the technique to the automotive industry to make quieter sunroofs, but he is is applying the knowledge to a new project involving tiny unmanned airplanes.

As part of a joint research project led by Caltech, Rowley is doing computational modeling, as well as building a controller, for aircraft that are the size of a typical model airplane. One day, the researchers hope, these aircraft will be able to fly with the speed of a bird and maneuver themselves with the three-dimensional agility of an insect.

Teresa Riordan | EurekAlert!
Further information:
http://www.princeton.edu

More articles from Process Engineering:

nachricht Quick, Precise, but not Cold
17.05.2017 | Fraunhofer-Institut für Lasertechnik ILT

nachricht A laser for divers
03.05.2017 | Laser Zentrum Hannover e.V.

All articles from Process Engineering >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can the immune system be boosted against Staphylococcus aureus by delivery of messenger RNA?

Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.

Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Marine Conservation: IASS Contributes to UN Ocean Conference in New York on 5-9 June

24.05.2017 | Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

 
Latest News

How herpesviruses win the footrace against the immune system

26.05.2017 | Life Sciences

Water forms 'spine of hydration' around DNA, group finds

26.05.2017 | Life Sciences

First Juno science results supported by University of Leicester's Jupiter 'forecast'

26.05.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>