Flow quality improvements in a blowdown wind tunnel 13; 13;

Acoustic baffles installed in the extended settling chamber of the NAL 1.2-m tunnel have substantially reduced the noise levels in its settling chamber and the SW test section. The quieter test-section flow has led to (1) a substantial improvement in the measurement accuracy of pulsation level data in air-intake models at supersonic speeds and (2) an improvement in light buffet onset measurement capability at subsonic/transonic speeds in the tunnel. However, the noise level in the PW test section is still high. Acoustic treatment of the plenum chamber aimed at mitigating the low-frequency tone observed in the PW test section is planned as a follow-on action. (CSA)