Modification to the NASA Langley 4- by 7-meter tunnel for improved rotorcraft aerodynamics and acoustics

Investigations have been conducted with the aim of improving circuit mean flow characteristics and test section turbulence intensity in the NASA Langley 4 x 7-m wind tunnel. Flow deflectors were instaled to displace the airstream and provide more symmetrical velocity distributions. The periodic flow pulsations of the open test section configuration were addressed by modifications of either the test section entrance, using triangular vanes, or the test section exit, using an alternative flow collector geometry; the latter proved more effective.