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针对直升机旋翼三维黏性流场特有的复杂环境,建立了一种基于欧拉法的旋翼三维水滴撞击特性计算的新方法。首先,在旋翼桨叶嵌套网格的基础上,发展了一套用于预测旋翼绕流流场的计算流体力学(CFD)模拟方法。然后,为克服传统直升机旋翼二维水滴撞击特性计算方法的不足,充分考虑旋翼流场的三维效应,在嵌套网格中基于欧拉法求解旋翼三维水滴撞击流场。其中,为解决尾流等区域的密度脉冲现象所引起的稳定性和收敛性问题,提出并建立了遮蔽区扩散模型。该模型通过判断遮蔽区变量,在计算域中动态生成遮蔽区域,并随迭代步数逐渐扩散。最后,通过与NACA0012翼型及国外UH-1H桨叶的试验和计算结果的对比,验证了旋翼三维水滴撞击特性计算新方法的可靠性,并进行了温度和水滴当量直径(MVD)对旋翼三维水滴撞击特性的影响分析。结果表明:遮蔽区扩散模型的加入,使二维情况的计算时间减少了22%,并增加了三维情况的计算稳定性,显著提高了旋翼三维水滴撞击特性的计算效率;沿着旋翼桨叶展向位置增大的方向,旋翼桨叶剖面水滴撞击范围有所增大,最大水滴局部收集系数呈先增加后减少再增加的变化趋势,其变化幅度接近50%;旋翼桨叶表面的水滴撞击区域和水滴局部收集系数随水滴当量直径的增加而增加。
A new method based on Eulerian method for calculating the three-dimensional droplet impingement of helicopter rotors is developed to deal with the complex environment inherent in the three-dimensional viscous flow field of helicopter rotors. Firstly, based on the nested grid of rotor blades, a set of computational fluid dynamics (CFD) simulation methods for predicting rotor flow field are developed. Then, in order to overcome the deficiency of traditional two-dimensional droplet impact characteristics of helicopter rotors and to fully consider the three-dimensional effect of rotor flow field, a three-dimensional rotor impinging flow field was solved based on Eulerian method in nested grids. Among them, in order to solve the stability and convergence problems caused by the density pulse phenomenon in wake and other regions, a model of shadowing region diffusion is proposed and established. The model dynamically generates occlusion regions in the computational domain by determining the variables of the occluded regions and gradually diffuses with the iteration steps. Finally, the reliability of the new method for calculating the three-dimensional droplet impingement of a rotor is verified by comparison with the experimental and computational results of the NACA0012 airfoil and the foreign UH-1H blade. The temperature and droplet equivalent diameter (MVD) Impact Analysis of Drop Impact Properties. The results show that the inclusion of the diffusion model in the shadow zone reduces the calculation time of two-dimensional case by 22% and increases the computational stability of the three-dimensional case, which improves the computing efficiency of the three-dimensional droplet impingement remarkably. In the direction of increasing position, the impact range of droplet of rotor blade is increased, and the maximum collection coefficient of local droplet first increases, then decreases and then increases, and the variation range is nearly 50%. The droplet impact area And the local collection coefficient of water droplets increases with the increase of droplet equivalent diameter.