SOME ACOUSTIC FEATURES OF PERFORATED TEST SECTION WALLS WITH SPLITTER PLATES

Transonic wind tunnels with perforated test section walls are generally known to have high noise levels. Calibration results of two large transonic wind tunnels [the Institute for Aeronautical Research (IAR) 1.5-m and T-38 1.5-m transonic wind tunnels] with walls that have slanted perforations with integral splitter plates have confirmed the effectiveness of splitter plates in suppressing edge-tone noise. However, as discovered in the T-38 wind tunnel, there are other wind tunnel components that generate flow disturbances. An experimental program, with the objective of identifying the sources of flow unsteadiness, has been performed in the T-38 wind tunnel. A comparison of the sources of flow unsteadiness between the IAR and the T-38 wind tunnels has been attempted.