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In order to address the issue of sudden changes in pressure and flow on the stability of the tethered UAV during high-rise firefighting, the water hammer effect in the vertical pipe cable during the start pump and pump stop was simulated using Bentley Hammer software. The vertical height of the pipe cable was controlled from 160 to 220 m, and the transportation flow was set from 260 to 320 L/min. The variation laws of pressure, flow and water hammer force at the locations of the pump and tethered UAV were analyzed. The results show that the water hammer phenomenon during the start pump and pump stops can be divided into the static/steady state stage, the sudden rise/drop stage, and the steady state/oscillation weakening stage. When starting the pump, the water hammer force at the ground pump end is proportional to the pipe cable height, with the maximum water hammer force increasing from 7 176.502 N to 8 413.785 N, indicating a stronger impact and a delayed response. The water hammer force of the UAV end is minimally affected by the pipe cable height. When the pump is stopped, the maximum water hammer force at the ground pump end increases with the pipe cable height, from 4 316.401 N to 7 219.388 N, increasing the risk of pipeline rupture. The reverse water hammer force at the UAV end is inversely proportional to the pipe cable height, decreasing from 10 616 N to 8 158.870 N, indicating that a lower pipe cable height is more likely to induce the UAV attitude instability. Regarding the transport flow, during pump start-up, the transport flow has a small impact on the peak water hammer force. When the pump is stopped, the peak water hammer force at the ground pump end is proportional to flow, increasing from 6 693.8 N to 7 541.606 N, increasing the risk of damage. The peak reverse water hammer force at the UAV end decreases with the increase of flow, from 9 866.063 N to 8 471.582 N. The smaller the flow rate, the more likely it is to cause damage to the tethering system.
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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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