In-flight simulation experiments on turbulent jet mixing noise

The effects of aircraft forward motion on pure turbulent mixing noise from unheated jets have been examined experimentally in the in-flight simulation mode. Both acoustic and flow characteristics were determined by testing model-scale nozzles in an anechoic free jet facility and a wind tunnel, respectively. Scaling laws were derived from each set of experiments and found to be complementary. The implications are discussed in detail. In particular, it is shown that the measured reduction in noise at 90° to the jet axis is a pure source alteration effect.