Acoustic control of free jet mixing

The paper reports a detailed study on the acoustic control of free jet mixing at realistic Reynolds numbers. The experimental results were obtained at Mach numbers of 0.3 and 0.8 and flow total temperatures up to 800 K. The Reynolds numbers ranged from 350,000 to 1,300,000. Excitation Strouhal numbers were in the range of 0.2 to 0.6. The experimental results are compared with predictions, based on an extension of the analysis by Tam and Morris. The results showed that proper upstream tone excitation enhances mixing of unheated jets for both high-speed, high Reynolds number conditions and for low-speed conditions. The heated jet, however, shows a response to upstream excitation that depends on jet Mach number. The agreement between the predictions and the experiments is very good for unheated jet conditions. However, for jets heated to temperatures above 600 K, the theoretical predictions differ from the experimental results.