PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Figuring out flow dynamics

Engineers gain insight into turbulence formation and evolution in fluids

2013-08-01
(Press-News.org) Turbulence is all around us—in the patterns that natural gas makes as it swirls through a transcontinental pipeline or in the drag that occurs as a plane soars through the sky. Reducing such turbulence on say, an airplane wing, would cut down on the amount of power the plane has to put out just to get through the air, thereby saving fuel. But in order to reduce turbulence—a very complicated phenomenon—you need to understand it, a task that has proven to be quite a challenge.

Since 2006, Beverley McKeon, professor of aeronautics and associate director of the Graduate Aerospace Laboratories at the California Institute of Technology (Caltech) and collaborator Ati Sharma, a senior lecturer in aerodynamics and flight mechanics at the University of Southampton in the U.K., have been working together to build models of turbulent flow. Recently, they developed a new and improved way of looking at the composition of turbulence near walls, the type of flow that dominates our everyday life.

Their research could lead to significant fuel savings, as a large amount of energy is consumed by ships and planes, for example, to counteract turbulence-induced drag. Finding a way to reduce that turbulence by 30 percent would save the global economy billions of dollars in fuel costs and associated emissions annually, says McKeon, a coauthor of a study describing the new method published online in the Journal of Fluid Mechanics on July 8.

"This kind of turbulence is responsible for a large amount of the fuel that is burned to move humans, freight, and fluids such as water, oil, and natural gas, around the world," she says. "[Caltech physicist Richard] Feynman described turbulence as 'one of the last unsolved problems of classical physics,' so it is also a major academic challenge."

Wall turbulence develops when fluids—liquid or gas—flow past solid surfaces at anything but the slowest flow rates. Progress in understanding and controlling wall turbulence has been somewhat incremental because of the massive range of scales of motion involved—from the width of a human hair to the height of a multi-floor building in relative terms—says McKeon, who has been studying turbulence for 16 years. Her latest work, however, now provides a way of analyzing a large-scale flow by breaking it down into discrete, more easily analyzed bits.

McKeon and Sharma devised a new method of looking at wall turbulence by reformulating the equations that govern the motion of fluids—called the Navier-Stokes equations—into an infinite set of smaller, simpler subequations, or "blocks," with the characteristic that they can be simply added together to introduce more complexity and eventually get back to the full equations. But the benefit comes in what can be learned without needing the complexity of the full equations. Calling the results from analysis of each one of those blocks a "response mode," the researchers have shown that commonly observed features of wall turbulence can be explained by superposing, or adding together, a very small number of these response modes, even as few as three.

In 2010, McKeon and Sharma showed that analysis of these blocks can be used to reproduce some of the characteristics of the velocity field, like the tendency of wall turbulence to favor eddies of certain sizes and distributions. Now, the researchers also are using the method to capture coherent vortical structure, caused by the interaction of distinct, horseshoe-shaped spinning motions that occur in turbulent flow. Increasing the number of blocks included in an analysis increases the complexity with which the vortices are woven together, McKeon says. With very few blocks, things look a lot like the results of an extremely expensive, real-flow simulation or a full laboratory experiment, she says, but the mathematics are simple enough to be performed, mode-by-mode, on a laptop computer.

"We now have a low-cost way of looking at the 'skeleton' of wall turbulence," says McKeon, explaining that similar previous experiments required the use of a supercomputer. "It was surprising to find that turbulence condenses to these essential building blocks so easily. It's almost like discovering a lens that you can use to focus in on particular patterns in turbulence."

Using this lens helps to reduce the complexity of what the engineers are trying to understand, giving them a template that can be used to try to visually—and mathematically—identify order from flows that may appear to be chaotic, she says. Scientists had proposed the existence of some of the patterns based on observations of real flows; using the new technique, these patterns now can be derived mathematically from the governing equations, allowing researchers to verify previous models of how turbulence works and improve upon those ideas.

Understanding how the formulation can capture the skeleton of turbulence, McKeon says, will allow the researchers to modify turbulence in order to control flow and, for example, reduce drag or noise.

"Imagine being able to shape not just an aircraft wing but the characteristics of the turbulence in the flow over it to optimize aircraft performance," she says. "It opens the doors for entirely new capabilities in vehicle performance that may reduce the consumption of even renewable or non-fossil fuels."

INFORMATION:

Funding for the research outlined in the Journal of Fluid Mechanics paper, titled "On coherent structure in wall turbulence," was provided by the Air Force Office of Scientific Research. The paper is the subject of a "Focus on Fluids" feature article that will appear in an upcoming print issue of the same journal and was written by Joseph Klewicki of the University of New Hampshire.

END



ELSE PRESS RELEASES FROM THIS DATE:

Understanding the effects of genes on human traits

2013-08-01
This news release is available in French. Recent technological developments in genomics have revealed a large number of genetic influences on common complex diseases, such as diabetes, asthma, cancer or schizophrenia. However, discovering a genetic variant predisposing to a disease is only a first step. To apply this knowledge towards prevention or cure, including tailoring treatment to the patient's genetic profile –also known as personalized medicine – we need to know how this genetic variant affects health. In a study published today in Nature Communications, ...

Chanel, UCSB's corpse flower, blooms and causes a big stink

2013-08-01
(Santa Barbara, Calif.) –– Chanel, UC Santa Barbara's corpse flower, has finally spread her odiferous wings, broadcasting a stench that smells like a cross between rotting flesh and Limburger cheese. "It's disgusting," said UCSB junior Connor Way, who visited Wednesday morning. "It's pretty nasty." Other visitors said Chanel smelled like "French cheese" or "a dead rat in a wall." Alex Feldwinn, a computer technician in the Life Science Computing Group at UCSB said, "It really smells like a dead animal –– not just a dead animal, but a rotting one." Edith Ogella, a longtime ...

Therapy for severe vasculitis shows long-term effectiveness

2013-08-01
Administering the drug rituximab once weekly for one month provides the same benefits as 18 months of daily immunosuppressive therapy in people with severe forms of vasculitis, or inflammation of the blood vessels, a study has found. Researchers from the Immune Tolerance Network (ITN), an international clinical trials group funded by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), found that rituximab is as effective as the standard therapy at inducing and maintaining disease remission. The findings appear ...

Fertility therapy not associated with long-term cardiovascular disease

2013-08-01
Women who gave birth following fertility treatment had no long-term increased risk of death or major cardiovascular events compared to women who gave birth without fertility therapy, according to new research by the Institute for Clinical Evaluative Sciences (ICES) and Women's College Hospital. The findings, published today in the Journal of the American College of Cardiology, are the first to show fertility medications, which can cause short-term pregnancy complications, are not associated with an increased risk of cardiovascular disease later in life. "The speculated ...

New Explorer mission chooses the 'just-right' orbit

2013-08-01
Principal Investigator George Ricker likes to call it the "Goldilocks orbit" — it's not too close to Earth and her Moon, and it's not too far. In fact, it's just right. And as a result of this never-before-used orbit — advanced and fine-tuned by NASA engineers and other members of the Transiting Exoplanet Survey Satellite (TESS) team — the Explorer mission led by Ricker will be perfectly positioned to map the locations of more than 500 transiting exoplanets, extrasolar planets that periodically eclipse each one's host star. When the two-year mission begins in the 2017-2018 ...

NASA technologist makes traveling to hard-to-reach destinations easier

2013-08-01
Traveling to remote locations sometimes involves navigating through stop-and-go traffic, traversing long stretches of highway and maneuvering sharp turns and steep hills. The same can be said for guiding spacecraft to far-flung destinations in space. It isn't always a straight shot. A NASA technologist has developed a fully automated tool that gives mission planners a preliminary set of detailed directions for efficiently steering a spacecraft to hard-to-reach interplanetary destinations, such as Mercury, Jupiter, Saturn, and most comets and asteroids. The tool, the ...

NASA finds powerful storms in quickly intensifying Tropical Storm Gil

2013-08-01
No sooner had Tropical Storm Flossie dissipated then another tropical cyclone called Tropical Depression 7E formed yesterday, July 30, in the eastern Pacific Ocean. NASA's TRMM satellite saw "hot towers" in the storm's center early on July 31, that indicated it would likely strengthen, and it became Tropical Storm Gil hours later. NASA and the Japan Space Agency's Tropical Rainfall Measuring Mission or TRMM satellite traveled above intensifying tropical storm Gil on July 31, 2013 at 0455 UTC or 12:55 a.m. EDT. The TRMM satellite pass showed that Gil was already very well ...

Satellite sees Flossie fizzle fast

2013-08-01
Tropical Depression Flossie fizzled fast on July 30 in the Central Pacific Ocean. Satellite imagery on July 31 showed remnant clouds northwest of the Hawaiian Island chain. NOAA's Central Pacific Hurricane Center issued the final advisory on the remnants of Tropical Depression Flossie on July 30 at 1500 UTC/11 a.m. EDT. At that time Flossie's remnant low pressure area was centered near 22.3 north latitude and 159.8 west longitude, about 140 miles west-northwest of Honolulu, Hawaii. The low pressure area was still moving to the west-northwest at 16 knots and the maximum ...

An interesting feature of the α-preformation probability was identified by Chinese researchers

2013-08-01
Probing the preformation of the α-particle in the α-decay process is a very attractive subject in studies of nuclear structure. Recently, this crucial α-preformation probability was empirically deduced and exhibits a new feature that had been inferred to some extent by Professor REN Zhongzhou and his group from Department of Physics, Nanjing University. This work, titled "Model-independent trend of α-preformation probability", was published in SCIENCE CHINA Physics, Mechanics & Astronomy 2013, Vol. 56(8). Dating back to the end of the 19th century, ...

Both parents experience highs and lows in sexuality after childbirth

2013-08-01
Partners of new mothers often experience shifts in sexuality, and these shifts are often unrelated to biological or medical factors pertaining to childbirth. The findings, which are published in a recent issue of The Journal of Sexual Medicine, expand current understanding of postpartum sexuality, and may help health professionals as they counsel new parents. Research on postpartum sexuality has typically focused on female reproductive biology in birth mothers—for example, how hormonal changes that accompany pregnancy, birth, and breastfeeding affect sexual desire, or ...

LAST 30 PRESS RELEASES:

Study tracks chromium chemistry in irradiated molten salts

Scientists: the beautiful game is a silver bullet for global health

Being physically active, even just a couple of days a week, may be key to better health

High-fat diet promote breast cancer metastasis in animal models

A router for photons

Nurses and AI collaborate to save lives, reduce hospital stays

Multi-resistance in bacteria predicted by AI model

Tinker Tots: A citizen science project to explore ethical dilemmas in embryo selection

Sensing sickness

Cost to build multifamily housing in California more than twice as high as in Texas

Program takes aim at drinking, unsafe sex, and sexual assault on college campuses

Inability to pay for healthcare reaches record high in U.S.

Science ‘storytelling’ urgently needed amid climate and biodiversity crisis

KAIST Develops Retinal Therapy to Restore Lost Vision​

Adipocyte-hepatocyte signaling mechanism uncovered in endoplasmic reticulum stress response

Mammals were adapting from life in the trees to living on the ground before dinosaur-killing asteroid

Low LDL cholesterol levels linked to reduced risk of dementia

Thickening of the eye’s retina associated with greater risk and severity of postoperative delirium in older patients

Almost one in ten people surveyed report having been harmed by the NHS in the last three years

Enhancing light control with complex frequency excitations

New research finds novel drug target for acute myeloid leukemia, bringing hope for cancer patients

New insight into factors associated with a common disease among dogs and humans

Illuminating single atoms for sustainable propylene production

New study finds Rocky Mountain snow contamination

Study examines lactation in critically ill patients

UVA Engineering Dean Jennifer West earns AIMBE’s 2025 Pierre Galletti Award

Doubling down on metasurfaces

New Cedars-Sinai study shows how specialized diet can improve gut disorders

Making moves and hitting the breaks: Owl journeys surprise researchers in western Montana

PKU Scientists simulate the origin and evolution of the North Atlantic Oscillation

[Press-News.org] Figuring out flow dynamics
Engineers gain insight into turbulence formation and evolution in fluids