Supersonic Jet Noise Reduction by Chevrons and Fluidic Injection

Abstract

This work focuses on the noise reduction capabilities of chevrons, fluidic injection, and a combination of both. The control mechanisms were experimentally investigated for over, under, and ideally expanded operating conditions. Acoustic far-field data was collected to quantify noise reductions and changes to the flow field through use of theoretical relations. Results show appreciable noise reduction by both fluidic injection and chevrons. Optimal performance of the two technologies occured at opposite ends of the operation envelope, with the chevrons performing better in the underexpanded regime and the fluidics in the overexpanded regime. The combination of the two technologies was also shown to achieve substantial noise reduction, but direct additive benefits were not always gained. This result is still important as it shows fluidic injection can be employed on complex geometry nozzles, such as that on the F-35, and still achieve noise reduction.

Aeroacoustic resonance and self-excitation in screeching and impinging supersonic jets – A review

“…This concept evolved into the modern chevron design, which has been the topic of many more recent studies. [130][131][132][133][134][135][136][137][138] While chevron technology has offered a sufficiently attractive trade-off between noise and thrust to justify their inclusion on a number of modern engines, a full phenomenological explanation of the mechanism by which they achieve this trade-off is yet lacking. From the perspective of screech, however, it seems likely that chevrons suppress resonance in much the same manner as tabs and notches: some combination of reduced hydrodynamic growth rates, reduced shock strength and reduced receptivity.…”

Simulations of rocket launch noise suppression with water injection from impingement pad

“…The injection of water at the inflow point does not directly produce sound at the input point since it is a steady injection. However, injection in general (gas or water) adds momentum that, in principle, can increase sound, but as in various gas injection cases such as that of Heeb et al 52 and Sinha et al, 53 it is believed that the momentum addition/exchange results in reducing the noise-producing large-scale structure in the jet. Similar effects of water injection are also pointed out by Kandula.…”

The suppression of hydrodynamic noise from underwater cavities by the change of back wall chamfer

“…Brenda Henderson shows that the water jet reduces the total sound pressure level by about 6 dB, and the gas jet can reduce the total sound pressure level by about 2 dB [4]. N. Heeb's experiments have shown that hydrodynamic noise can be reduced by both jet injection and serrated construction [5]. Yiping Wang found that the upstream concave surface can effectively suppress the cavity flow oscillation [6].…”