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 A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes
20.07.2018 | Science China Press

nachricht Future electronic components to be printed like newspapers
20.07.2018 | Purdue University

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: Future electronic components to be printed like newspapers

A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.

The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...

Im Focus: First evidence on the source of extragalactic particles

For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.

To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...

Im Focus: Magnetic vortices: Two independent magnetic skyrmion phases discovered in a single material

For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.

Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...

Im Focus: Breaking the bond: To take part or not?

Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.

A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...

Im Focus: New 2D Spectroscopy Methods

Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.

"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Leading experts in Diabetes, Metabolism and Biomedical Engineering discuss Precision Medicine

13.07.2018 | Event News

Conference on Laser Polishing – LaP: Fine Tuning for Surfaces

12.07.2018 | Event News

11th European Wood-based Panel Symposium 2018: Meeting point for the wood-based materials industry

03.07.2018 | Event News

 
Latest News

A smart safe rechargeable zinc ion battery based on sol-gel transition electrolytes

20.07.2018 | Power and Electrical Engineering

Reversing cause and effect is no trouble for quantum computers

20.07.2018 | Information Technology

Princeton-UPenn research team finds physics treasure hidden in a wallpaper pattern

20.07.2018 | Materials Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>