地面效应中垂直起降状态旋翼的气动特性计算

Aerodynamics Characteristics Prediction for Axial Flying Rotor in Ground Effect

基于时间步进自由尾迹和地面面元模型,构建了一种新的非定常空气动力学模型,用于计算有地效垂直飞行状态下的旋翼气动性能。为提高瞬态尾迹结构的求解稳定性和计算速度,本文使用了精度阶数更高的显式CB3D格式。计算证实,该格式能有效控制地面干扰所产生的数值误差,得到的尾迹结构也更符合物理实际。同时引入一种适用于非定常状态的"等体积修正"方法,以对计算中容易出现的涡线落入地面下方的非物理现象进行修正。在有地效状态下,将新构建模型的计算结果同试验数据进行了对比,验证了模型的准确性。进而计算了平面与斜面上有地效垂直起降状态下旋翼气动特性的变化特点,分析了其影响因素。

A new transient aerodynamics model is founded based on time-stepping free-wake and ground panel models for rotor performance prediction in axial flying condition in ground effect. A 3rd-order CB3D scheme is used to improve the calculation stability and efficiency of wake geometry. The prediction reveals that CB3D scheme can inhibit the numerical errors caused by ground effectively and get a more truthful wake geometry. A ＂constant volume rectification＂ method is also incorporated into the model to rectify the wake vortices falling below the ground unphysically in transient state. The predicted result of the new model is compared with experimental data to validate its accuracy. Then the aerodynamics characteristics of rotor in axial flying near flat or inclined ground are analyzed.