Living in relatively close proximity to two major airports, I’m all too aware of the problem of jet noise. But if you’ve been to air show or live near an air force base, the problem worsens because now you’re dealing with sonic booms from planes flying at speeds exceeding the speed of sound.
University of Buffalo aerospace engineer James Chen is researching the noise issues arising from very high jet speeds. Chen, assistant professor in the Department of Mechanical and Aerospace Engineering at UB’s School of Engineering and Applied Sciences, helped author a study in the Journal of Engineering Mathematics that extends classic kinetic theory into high-speed aerodynamics, including hypersonic speed.
The research is being conducted as interest in high-speed passenger jets and unmanned aerial vehicles traveling at the speed of sound is again drawing interest. The idea is not new—for instance, the Concorde flew from 1976 through 2003 but was grounded due to high operating costs and noise complaints.
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, whose work is funded by the U.S. Air Force’s Young Investigator Program, which supports engineers and scientists who show exceptional ability and promise for conducting basic research.
One issue is airflow. “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,” says Chen.
To solve these complex problems, researchers have historically used wind tunnels, which 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).
“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.
His work in the Journal of Engineering Mathematics centers on morphing continuum theory (MCT), which is 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, everything from the vehicle’s shape to what materials it is made of. The goal, says Chen, is a new class of aircraft which are faster, quieter, less expensive to operate and safer.