Control methods for supersonic jet screech tones

Several methods on controlling supersonic jet screech tones are experimentally compard. The tested nozzle configuration consists of Delta-Tabs and chevrons. The experimental results show that the nozzles, with Delta-Tabs or Chevrons, distinctly decrease the amplitude of screech tones. The Delta-Tab nozzle also influences the modes of screech tones. However, screech tones still exist and dominate in the upstream direction. Based upon the experimental investigation, the compound nozzle, Delta-Tab plus chevron, is proposed. It is demonstrated that the compound nozzle totally eliminates screech tones. Furthermore, the compound nozzle can also reduce, to some extent, the intensities of other components of supersonic jet noise. In addition, thrust losses of nozzles in the paper have been evaluated. The results show that the thrust loss of compound is about 3% between the chevron and Delta-Tabs.