Scott E. Munro’s research while affiliated with Georgia Institute of Technology and other places

Circulation control technology uses tangential blowing around a rounded trailing edge or a leading edge to change the force and moment characteristics of an aerodynamic body. This technology has been applied to circular cylinders, wings, helicopter rotors, and even to automobiles for improved aerodynamic performance. Only limited research has been conducted on the acoustic of this technology. Since wing flaps contribute to the environmental noise of an aircraft, an alternate blown high lift system without complex mechanical flaps could prove beneficial in reducing the noise of an approaching aircraft. Thus, in this study, a direct comparison of the acoustic characteristics of high lift systems employing a circulation control wing configuration and a conventional wing flapped configuration has been made. These results indicate that acoustically, a circulation control wing high lift system could be considerably more acceptable than a wing with conventional mechanical flaps.

Circulation control wings are a type of pneumatic high-lift device that have been extensively researched as to their aerodynamic benefits. However, there has been little research into the possible airframe noise reduction benefits of a circulation control wing. The key element of noise is the jet noise associated with the jet sheet emitted from the blowing slot. This jet sheet is essentially a high aspect-ratio rectangular jet. A recent study on high aspect-ratio jet noise was performed on a nozzle with aspect-ratios ranging from 100 to 3,000. In addition to the acoustic data, fluid dynamic measurements were made as well. This paper uses the results of these two studies and attempts to develop a prediction scheme for high aspect-ratio jet noise

Circulation control wings are a type of pneumatic high-lift device that have been extensively researched as to their aerodynamic benefits. However, there has been little research into the possible airframe noise reduction benefits of a circulation control wing. The key element of noise is the jet noise associated with the jet sheet emitted from the blowing slot. This jet sheet is essentially a high aspect-ratio rectangular jet. Thus, to fully understand the noise of a circulation control wing, the noise of high aspect-ratio rectangular jets must also be understood. A high aspect-ratio nozzle was fabricated to study the general characteristics of high aspect-ratio jets with aspect ratios from 100 to 3000. The jet noise of this nozzle was proportional to the 8" power of the jet velocity. It was also found that the jet noise was proportional to the slot height to the 312 power and slot width to the 1/2 power.

The objective of this study was to acquire acoustic and flow data with hard and lined duct wall sections for % situation of a liner prediction code being developed at NASA LaRC. Both the mean and acoustic flowfields were determined in a cross-plane of the rectangular duct. The test liner was of the locally-reacting type and w as made from a ceramic material. The material, consisting of a tubular structure, was provided by NASA LaRC. Flow measurements included pressure, temperature, and velocity profiles upstream of the liner section. The inflow sound pressure levels and phases were obtained with a microphone probe equipped with a nose cone in two cross planes upstream of the liner and in two cross plane downstream of the liner. In addition to the acoustic measurements at the cross planes, axial centerline acoustic data was acquired using an axially traversing microphone probe that was traversed from a Location upstream of the liner to some distance downstream of the liner. Much of the data was acquired for frequencies of 500, 1000, 1500, 2000 and 2500 Hz and for duct mean flow Mach numbers of 0.0, 0.1, 0.2, and 0.3.

Issued as final report This item was temporarily removed from SMARTech at the request of the Georgia Tech Research Institute on May 8, 2009.