基于CFD和混合配平算法的直升机旋翼地面效应模拟

发布时间：2018-04-25 21:43

本文选题：旋翼 + 地面效应　；参考：《航空学报》2016年08期

【摘要】：建立了一套基于非结构网格技术和动量源模型的直升机旋翼计算流体力学(CFD)方法,用来模拟贴地飞行时直升机旋翼非定常气动特性。其中,控制方程采用三维Navier-Stokes方程,空间方向上采用Jameson格式,时间方向上采用五步Runge-Kutta迭代法,选用Spalart-Allmaras湍流模型。旋翼对流场的作用采用动量源项模拟,为更真实地模拟地面效应(IGE)的作用,采用了"移动地面"的物面边界来代替常规的"固定地面"边界,并对旋翼附近及旋翼与地面之间的网格进行加密处理,以提高地面涡的捕捉精度。考虑实际飞行环境下旋翼的运动和操纵,在流场计算时考虑旋翼配平特性。其中,配平方程的旋翼气动力通过CFD方法和动量-叶素组合理论模型的耦合计算给出,为了提高配平方法的鲁棒性和效率,提出并建立了基于遗传算法/拟牛顿法的高效混合迭代算法。运用所建立的方法,首先,选用有试验结果可供对比的算例计算了地面效应作用下的旋翼拉力增益、功率变化,验证了计算方法的有效性,解决了涡流理论方法较难模拟的"小速度前飞旋翼需用功率突增"问题。然后,着重研究了UH-60A直升机旋翼在不同离地高度、不同前进比状态,旋翼需用功率、诱导速度、地面涡及旋翼操纵的变化规律。计算结果表明:地面涡出现在较小的前进比范围内,随前进比的增大,地面涡在纵向平面将顺来流方向移动,在轴向方位靠近地面方向移动,直至最后不断减弱消失。
[Abstract]:Based on unstructured grid technology and momentum source model, a computational fluid dynamics (CFD) method for helicopter rotor was developed to simulate the unsteady aerodynamic characteristics of helicopter rotor during landing flight. Among them, the governing equation adopts three-dimensional Navier-Stokes equation, Jameson scheme is used in spatial direction, five-step Runge-Kutta iteration method is used in time direction, and Spalart-Allmaras turbulence model is selected. Momentum source term is used to simulate the effect of rotor flow field. In order to simulate the effect of ground effect more realistically, the surface boundary of "moving ground" is used to replace the conventional "fixed ground" boundary. The meshes near the rotor and between the rotor and the ground are encrypted to improve the accuracy of the surface vortex capture. Considering the motion and control of the rotor in the actual flight environment, the flattening characteristic of the rotor is taken into account in the calculation of the flow field. In order to improve the robustness and efficiency of the balancing method, the rotor aerodynamic force of the balancing equation is obtained by the coupling calculation of the CFD method and the combination of momentum and leaf element model. An efficient hybrid iterative algorithm based on genetic algorithm / quasi-Newton method is proposed and established. Using the established method, first of all, the rotor tension gain and power change under ground effect are calculated by using an example with experimental results to compare the results, and the validity of the calculation method is verified. In this paper, the problem of "small speed forward rotor needs sudden increase", which is difficult to simulate by eddy current theory method, is solved. Then, the variation of rotor power, induction speed, ground vorticity and rotor control of UH-60A helicopter at different ground height and forward ratio are studied. The results show that the surface vortices appear in a small forward ratio range, and with the increase of the forward ratio, the surface vortices will move in the longitudinal plane in the direction of downstream flow, and move in the axial direction near the ground direction, until finally the surface vortices will continue to weaken and disappear.
【作者单位】：南京航空航天大学直升机旋翼动力学国家级重点实验室;
【基金】：国家自然科学基金(11272150)~~
【分类号】：V275.1

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