Researchers are working to solve the deafening noise problems associated with aircraft exceeding the speed of sound, roughly 767 mph.
“Imagine flying from New York City to Los Angeles in an hour. Imagine incredibly fast unmanned aerial vehicles providing more updated and nuanced information about Earth’s atmosphere, which could help us better predict deadly storms,” says James Chen, an assistant professor in the mechanical and aerospace department at the University at Buffalo’s School of Engineering and Applied Sciences.
The study pertains to Austrian physicist Ludwig Boltzmann’s classical kinetic theory, which uses the motion of gas molecules to explain everyday phenomena, such as temperature and pressure. Chen’s work extends classical kinetic theory into high-speed aerodynamics, including hypersonic speed, which begins at 3,836 mph or roughly five times the speed of sound.
The idea of supersonic passenger jets is not new. Perhaps the most famous is the Concorde, which flew from 1976-2003. While successful, noise complaints and expensive operating costs dogged the plane. More recently, Boeing announced plans for a hypersonic airliner and NASA is working on a supersonic project called QueSST, short for Quiet Supersonic Technology.
“Reduction of the notorious sonic boom is a just a start. In supersonic flight, we must now answer the last unresolved problem in classical physics: turbulence,” says Chen.
To create more efficient, less expensive and quieter aircraft that exceed the sound barrier, the research community needs to better understand what is happening with the air surrounding these vehicles.
“There is so much we don’t know about the airflow when you reach hypersonic speeds. For example, eddies form around the aircraft creating turbulence that affect how aircraft maneuver through the atmosphere,” he says.
To solve these complex problems, researchers have historically used wind tunnels, which are research laboratories that replicate the conditions vehicles encounter while in the air or space. While effective, these labs can be expensive to operate and maintain.
As a result, many researchers, including Chen, have pivoted toward direct numerical simulations.
“DNS with high-performance computing can help resolve turbulence problems. But the equations we have used, based upon the work of Navier and Stokes, are essentially invalid at supersonic and hypersonic speeds,” says Chen.
The new work centers on morphing continuum theory, based on the fields of mechanics and kinetic theory. MCT aims to provide researchers with computationally friendly equations and a theory to address problems with hypersonic turbulence.
Ultimately, the work could lead to advancements into how supersonic and hypersonic aircraft are designed, including the vehicle’s shape and what materials engineers use to make it. The goal, he says, is a new class of aircraft which are faster, quieter, less expensive to operate, and safer.
Funding for the work came from the US Air Force’s Young Investigator Program, which supports engineers and scientists who show exceptional ability and promise for conducting basic research.
The research appears in the Journal of Engineering Mathematics.
Source: University at Buffalo
