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 Researchers use light to remotely control curvature of plastics
23.03.2017 | North Carolina State University

nachricht TU Graz researchers show that enzyme function inhibits battery ageing
21.03.2017 | Technische Universität Graz

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: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>