Abstract:
In the present investigation, sound-pressure levels radiated from the twin- and multijet with a square configuration were measured at various pressure ratios R from 2.00 to 6.33. The nozzle diameter was 5 mm and the center-to-center spacing of the nozzles was fixed to 1.4 times the nozzle diameter. From this experiment, it is found that the overall sound-pressure level (OASPL) radiated from the multijet with a square configuration becomes lower than that from the twin jet for the pressure ratio range R>4.0. In the near sound field upstream of the nozzle exit, the difference of the OASPL between the twin- and multijet with a square configuration reaches a maximum (about 7 dB) at the pressure ratio about R=5.0. This decreasing of the OASPL may be caused by the shielding of the sound waves radiated from the inner part of the multijet with a square configuration by the surrounding four jets, and by stabilizing the jet oscillation due to the appropriate coupling process among four jets. [Work supported by the Ministry of Education and Culture of Japan (Grant No. C2-08650201).]