关键词: 双射流+;声屏蔽;啸声;纹影摄影

Abstract: The effects of arrangements of twin jets on the acoustical characteristics were investigated by the schlieren visualization, noise measurement and theoretical analysis. For under-expanded supersonic twin jets, the fundamental frequencies and modes were similar to those for a single jet; The pressure ratios corresponding to switching from one mode to another mode were different compared with the single jet. Due to three-dimensional flow characteristics, acoustical properties were different in different azimuthal measurement planes. Shielding occurred for under-expanded supersonic twin jets, especially for the helical screech mode C. The shielding reduced the screech intensities most effectively in the upstream and downstream directions near the jet axis. The noise attenuation can be achieved by acoustical shielding.

Key words: Twin jets~+;Acoustic screening;Whistler;Schlieren photography