Effects of Rotor Wheelbase on Downwash Flow Aggregation and Wind-resistance
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摘要: 旋翼轴距对下洗气流的聚合流动有重要影响。依据下洗气流形成过程，研究下洗气流与涡团挤压效果和涡干涉下洗气流低压聚合效应，并定义了旋翼下洗气流聚合度。采用Realizable k-ε湍流模型与滑移网格计算方法，并进行风速试验验证，探究多旋翼下洗气流间的聚合流动特性并分析下洗气流在不同聚合程度下的抗风扰能力。结果表明：多旋翼间隙内近地涡团的压缩是下洗气流间发生聚合现象的关键特征，下洗气流聚合现象使下游气流速度分布更加均匀，提高气流流动的稳定性。悬停状态下，旋翼距径比为1.1至1.4范围时，旋翼距径比越高，聚合程度越低。气流聚合现象有利于抵抗前飞来流的干扰，但前飞速度超出某一临界值时，下洗气流向下的流动形态被破坏，聚合现象对来流风扰的抵抗作用被削弱。Abstract: A rotor wheelbase has an important influence on the downwash flow aggregation. According to the downwash flow formation, the effects of downwash flow and vortex compression and downwash aggregation were analyzed. The realizable k-ε turbulence model and sliding mesh were used, and the simulation model was verified. The rotor wheelbase's downwash flow aggregation characteristics and wind resistance ability below different aggregation degrees were analyzed. The simulation results show that the near-ground vortex compression between rotor gaps is crucial to the downwash flow aggregation phenomenon, which makes the downwash flow velocity distribution more uniform and increases the flow stability. When the rotor wheelbase is hovering and the wheelbase-to-diameter ratio is 1.1 to 1.4, the higher the wheelbase-to-diameter ratio, the lower the flow aggregation degree. The downwash flow aggregation phenomenon is useful for resisting the interference of pre-flight flow, however, when the forward flight speed exceeds a certain critical value, the downward flow pattern is destroyed, and the resistance of the downward flow aggregation phenomenon to wind is weakened.
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表 2 测试点z向速度计算值与试验值比对
高度/m 旋翼1速度 旋翼2速度 旋翼3速度 旋翼4速度 计算值/
(m·s-1)试验值/
(m·s-1)误差/
%计算值/
(m·s-1)试验值/
(m·s-1)误差/
%计算值/
(m·s-1)试验值/
(m·s-1)误差/
%计算值/
(m·s-1)试验值/
(m·s-1)误差/
%0.8 6.831 7.414 7.9 6.774 7.248 6.5 7.132 7.692 7.3 7.280 7.573 3.9 0.5 5.668 6.191 8.4 6.283 6.561 4.2 6.467 6.763 4.4 6.625 6.224 6.4 
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