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摘要:
直升机旋翼与地面复杂干扰流场诱导沙床沙粒运动，形成沙盲现象，然而侧风改变旋翼与地面干扰流场，改变沙云形态和沙盲现象。因此，将侧风作用项嵌入基于黏性涡粒子的旋翼/地面气动干扰模型，体现侧风对旋翼与地面干扰流场的作用，并基于离散单元法的沙粒动力学模型，增加侧风引起的气动力，体现侧风对沙粒运动的作用。研究侧风对直升机前飞沙盲特性的影响，并分析侧风速度、风向对直升机沙盲特性的影响规律。结果表明：侧风对直升机沙盲沙云形态影响显著，且左侧风显著增强沙尘浓度，而迎风状态减小沙尘浓度；随着侧风速度的增加，左侧风状态下的沙尘浓度先增加后减小。
Abstract:The complex interaction flow between the helicopter rotor and ground induced the movement of sand particles in the sand bed and then yielded helicopter brownout. However, a crosswind will change the rotor-ground interaction flow field, and influence the brownout. Therefore, a crosswind is coupled into the helicopter rotor-ground aerodynamic model based on viscous vortex particles to consider the influence of the crosswind on the rotor-ground interaction flow field. In order to take into account how the crosswind affects sand movement, the air force caused by the crosswind is also incorporated to the sand particle dynamic model based on DEM. Then, the effect of the crosswind on the process of helicopter brownout at forward flight is analyzed, and the influences of velocity, and direction of the crosswind on the brownout are also investigated. Results show that the crosswind has a significant influence on the helicopter brownout, the density of dust cloud obviously increases with the crosswind at the port side, and it is restrained at forward flight. The density of the dust cloud firstly increases and then decreases with increasing the velocity of crosswind at the port side.
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Key words:
- crosswind /
- brownout /
- rotor-ground aerodynamic interaction /
- discrete element method /
- helicopter
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图 9 有无侧风直升机xz截面流场
Figure 9. Flow field of helicopter with and without crosswind (xz plane)
图 10 有无侧风直升机后方流场(x=2R)
Figure 10. Flow field behind of helicopter with and without crosswind (x=2R)
图 12 沙尘浓度随风向角的变化
Figure 12. Variations of density of dust cloud with crosswinds at different directions
图 13 不同风向角的直升机沙云俯视图
Figure 13. Dust cloud of helicopter with crosswinds at different directions at top view
图 14 不同风向角的直升机沙云正视图
Figure 14. Dust cloud of the helicopter with crosswinds at different directions at front view
图 15 沙尘浓度随风速的变化
Figure 15. Variations of density of dust cloud at different velocities
图 17 不同风速的直升机沙云俯视图(θ=−90º)
Figure 17. Dust cloud of helicopter with different velocities at top view (θ=−90º)
图 18 不同风速的直升机沙云正视图(θ=−90º)
Figure 18. Dust cloud of helicopter with different velocities at front view (θ=−90º)
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