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Hazardous noise of flight deck due to jet blast deflector impingement causes a serious damage to the health of crew members. An experiment of jet impinging on a blast deflector was carried out in a full anechoic chamber to study the acoustic characteristics. With a diameter (D) of 56.4 mm, a convergent nozzle was used to investigate a Mach number of 1.01 jet impingement. Flow visualization and far-field microphones were employed to observe the flow field and measure the far-field noise, respectively. The test was performed on a 600 mm×600 mm deflector and with three inclined angles (β) of 45°, 55°and 65°. The results show that the impact angle has a significant influence on the wall jet structure and overall sound pressure level (OASPL). With the increase of impact angle, the OASPL of upstream and downstream rise and fall respectively. It is found that the OASPL increases by 15 dB in the upstream direction and decreases by 7 dB in the downstream direction for β=65°. Flow visualization and spectra analysis indicate that downstream directions are radiated by low frequency noise originated from trailing edge of the deflector due to separation of the large scale vortex. Specifically, it can be illustrated by correlation analysis that the directivity of the trailing separation noise becomes more significant when the impact angle reduces. Upstream directions are dominated by impingement noise. Although impingement noise is significantly affected by impact angle, the radiation structure of impingement acoustic wave under different impact angles is similar to each other according to the correlation analysis. In addition, the deflector forms a low-pass filtering effect on the impingement noise, and the sideline spectra have steep peaks. The OASPL and spectra of sideline directions are less affected by the impact angle. The research results are expected to be helpful for noise pollution control on carrier deck.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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