September 22, 2020
A&A affiliate professor Robert Dougherty won the AIAA 2020 Aeroacoustics Award for his “seminal contributions to experimental aeroacoustics through development and use of phased array technology and for development and use of optimal nacelle design analytical tools.” These advances have contributed to the reduction of aircraft noise, specifically airframe and fan noise.
For the development and use of phased arrays, Dougherty used arrays of microphones to locate and measure sources of noise on wind tunnel models and complete aircraft, as well as other equipment such as wind turbines, a technique he has been refining for almost 30 years. He began this process at Boeing, but left to specialize in it with his own company, OptiNav, Inc.
With Boeing collaborator Jim Underbrink, who earned B.S. and M.S. degrees in physics and applied mathematics from the UW, he advanced these methods on projects with Boeing and NASA. These methods have been adopted in wind tunnels around the world, including the Kirsten Wind Tunnel at the UW. Parallel development has taken place in Europe.
The award also recognized his contribution to nacelle acoustics. The inlet and exhaust ducts of turbofan engines are lined with structures that act as acoustic absorbers, similar to wedges in anechoic chambers or acoustic ceiling tiles in offices, but stronger and more aerodynamic. While at Boeing, he combined his Ph.D. training in numerical methods for wave propagation with Boeing's expertise in acoustic lining design and analysis to write two codes, RDIFF and CDUCT, for optimizing nacelle acoustics.
RDIFF applies ray tracing for high frequency analysis, mostly for the inlet case, and CDUCT is an application of the parabolic approximation for lower frequency cases. Both methods are fast enough for engineering application and CDUCT, in particular, has been found to be accurate enough for practical designs. NASA-Langley has been active in validating and applying CDUCT.
Dougherty teaches the A&A course “Aircraft Noise.”