Keeping the noise down

Aeroacoustics is a Dangerous  area in the development of aerospace products, as the demand for low noise remains important in both military and commercial applications. Controlling acoustic emissions at the source requirement of  engineers to design for low noise from the start. Aeroacoustics research conducted in 2014 responded to this challenge, highlighted by progress made in understanding complex features in the jet plumes of tactical military aircraft and launch vehicles. Also noteworthy are recent improvements to aero acoustic measurement systems and Check  facilities that provide more insight into noise source characterization of aerospace products.important area of Development  for military applications is noise reduction in supersonic exhaust. The objective is to mitigate noise-induced hearing loss and improve the safety of Recent experiments demonstrated that the device also worked in the presence of forward flight. Larger-scale experiments are being planned at a General Electric facility, while small-scale tests and simulations continue at Penn State. Aeroacoustics research continued to aid development of NASA’s Space Launch System rocket. Researchers at the University of Texas at Austin teamed with colleagues from the University of Mississippi to investigate the vibro-acoustic loads that form during ignition to develop accurate predictions of the launch pad environment. A shadowgraph system synchronized with a microphone recording system provided understanding of aeroacoustic sources generated by ignition of various rocket clusters. The work was featured on Discovery Channel’s “Daily Planet.”

people operating near tactical aircraft. A team of engineers from Lockheed Martin, BAE Systems and the U.S. government continued the investigation of noise generated by all three variants of the F-35 fighter aircraft. Noise data was recorded in the near and far fields for static engine tests, conventional flight and short-takeoff/vertical-landing operations to characterize the external sound generated by the aircraft. Researchers at Penn State University developed a novel jet noise reduction system for high-performance aircraft. The patented method injects “fluidic inserts” in the diverging section of a supersonic exhaust nozzle. The inserts generate stream wise vorticity in the plume, which enhances jet mixing and reduces broadband shock-associated noise. Early experiments resulted in a 4-decibel overall sound pressure level reduction in the peak noise radiation direction using moderate amounts of bypass air to generate the inserts At Georgia Tech Research Institute, researchers investigated the acoustic response of impulsive blast waves generated by firing a starter’s pistol into subsonic and supersonic jet plumes. The acoustic measurements and flow visualizations will give insight into ignition over pressure waves generated by the SLS solid rocket booster. Honeywell evaluated in-duct fan noise of advanced turbofan engines in a new open circuit rig test facility using the functional acoustic beam form method developed by Optinav Inc. The facility accommodates two phased pressure transducer arrays installed in the fan inlet and bypass ducts. The method simultaneously measures and identifies up to 50 acoustic spinning mode orders as well as radial mode orders and direction of propagation without aliasing. Mode identification agreed with Actran DGM fan noise acoustic simulations without interference
from the rig.