Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Understanding Turbulence In The Fast Lane at Mach 10 And Beyond

17.03.2005


Although NASA’s X-43A and other hypersonic airplanes use air-breathing engines and fly much like 747s, there’s a big difference between ripping air at Mach 10 (around 7,000 mph) and cruising through it at 350 mph.

These differences are even more pronounced when hypersonic aircraft sip rarified air at 100,000 feet, while commercial airliners gulp the much thicker stuff at 30,000. Aero-thermodynamic heating is a very big deal at Mach 10. The critical point comes where air changes from flowing smoothly across a surface < laminar flow < to when it becomes chaotic < turbulent flow.

Aero-thermodynamic heating largely determines the engine size, weight, choice of materials and overall size in hypersonic airplanes. So engineers would like to have a much better understanding of what triggers turbulence and how they can control it at hypersonic speeds. Air goes from laminar to turbulent at what engineers call the "boundary layer." They understand how this happens at slower speeds, but they’re still grappling with which factors influence it at hypersonic speeds.



University of Arizona Associate Professor Anatoli Tumin, of Aerospace and Mechanical Engineering (AME), is among those studying the problem and has developed a model that predicts the surface roughness effects on the transition from laminar to turbulent flow at hypersonic speeds. His theory has a lot to do with partial differential equations, Navier-Stokes equations and other brain-taxing mathematics that Tumin and Applied Math Ph.D. student Eric Forgoston have grappled with during the past couple of years. "In principle, the theory tells us what the optimal perturbations are that will lead to turbulent flow," Tumin said. "Now we can explore different geometries for roughness elements to see which are best. We can explore how to space them and where we should position them."

The researchers will soon run a supercomputer simulation to compare their theory with what actually happens when air flows across a roughened surface at hypersonic speeds. Currently, these simulations guzzle tens of hours of supercomputing time. But if Tumin’s theory is correct, engineers will soon get the same results from their office laptops. Tumin is working with Research Assistant Professor Simone Zuccher, of UA AME, to develop a software package that will allow designers to do this laptop-style analysis. The software will help them predict when and where the transitions from laminar to turbulent flow occur in engines and on surfaces operating at hypersonic speeds. "We developed our theory and arrived at what is called the ’transient growth mechanism,’" Tumin said. "The airflow is stable, but there are some tiny disturbances within it that can grow downstream. We can generate these downstream, streamwise vortices (spiraling flows) by using the correct amount of roughness in the right places. We can do this at an engine inlet, for instance, in order to trip the boundary layer and to have stable engine performance." "If we can understand the laminar-turbulent transition mechanism, we can predict the transition point accurately," Tumin said. "This is important for heat protection, where you want laminar flow. Otherwise, you need to add a lot of weight for thermal insulation because you have to assume turbulent flow at the surface when you do your design calculations. Similarly, engine designers would like to have a quick transition to turbulence to have a turbulent flow at an engine inlet."

Ultimately, better understanding the transition to turbulence at hypersonic speeds will allow designers to build lighter, faster, more efficient airplanes capable of traveling at even higher speeds of Mach 15 or more.

Contact Information:

Anatoli Tumin
Associate Professor
Aerospace and Mechanical Engineering
tumin@email.arizona.edu

Ed Stiles | UA College of Engineering
Further information:
http://uanews.org/engineering
http://www.nasa.gov/missions/research/x43-main.html
http://www.arizona.edu

More articles from Power and Electrical Engineering:

nachricht Multicrystalline Silicon Solar Cell with 21.9 % Efficiency: Fraunhofer ISE Again Holds World Record
20.02.2017 | Fraunhofer-Institut für Solare Energiesysteme ISE

nachricht Six-legged robots faster than nature-inspired gait
17.02.2017 | Ecole Polytechnique Fédérale de Lausanne

All articles from Power and Electrical Engineering >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Start codons in DNA may be more numerous than previously thought

21.02.2017 | Life Sciences

An alternative to opioids? Compound from marine snail is potent pain reliever

21.02.2017 | Life Sciences

Warming ponds could accelerate climate change

21.02.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>