CFD在螺旋桨飞机滑流影响研究中的应用

通过求解绝对坐标系下的非定常雷诺平均Navier-Stokes方程，计算了非定常滑流对某飞机巡航构型低速状态的气动特性影响。为描述螺旋桨桨叶的相对运动，采用了动态重叠网格技术，并在并行环境下采用全隐式双时间步方法和多重网格技术来保证时间精度和提高计算效率。将计算结果与试验结果相比较，在线性段，计算得到的升力系数与试验值总体偏差不超过2%，阻力系数相对试验值而言整体偏大，基本控制在8%左右，俯仰力矩系数的计算结果与试验值趋势一致。总结了滑流对螺旋桨飞机宏观气动特性的影响规律，由于滑流在空间发展过程中不断与周围空气相混合，使得滑流边界逐渐"模糊"，因此滑流流管在空间发展过程中的巨大畸变对滑流影响的分析工作带来了难度。针对这种现象，本文将有/无滑流的流场进行对比，通过当地动压增量来定义滑流的加速效应边界，以及通过当地气流角增量来定义滑流的洗流效应边界。该方法能较好地捕捉和解释由于滑流对飞机部件干扰而使得飞机方向安定性呈现的非线性现象，初步揭示了螺旋桨滑流复杂尾迹流动的特点，在螺旋桨飞机非定常滑流影响机理研究方面具有一定的参考价值。

Application of CFD in slipstream effect on propeller aircraft research

By solving unsteady Reynolds-averaged Navier-Stokes equations in absolute coordinate system, the effect of propeller slipstream on aerodynamics characteristics of a cruise configuration is studied. Moving overlapping grid technology is adopted to simulate the movement of blades. The fully implicit dual-time method and the multi-grid scheme are used in parallel environment to enhance the calculation efficiency. Comparing with the experimental values in linear region, the lift coefficients of the numerical simulation deviate from the experimental values around 2%; the calculated drag coefficients are relatively large at around 8%; and the pitching moment coefficients are in accordance with the trend of the experiments. The law of influence of slipstream on propeller aircraft is summed up. As the slipstream keeps mixing with the surrounding air during the spatial development, the boundary becomes smeared. As a result, the malformation of the developing slipstream tube affects the analysis of the effect of aircraft. To fix the above problems, flow-fields with and without slipstream are compared. The acceleration effect boundary of the slipstream is acquired by measuring the increments of local dynamic pressure and the wash effect boundary of the slipstream is obtained by measuring the local airflow angle increments. This method can better capture and explain the nonlinear phenomenon of the stability of the propeller aircraft caused by the interference of slipstream on aircraft components. Also, the wake convection and evolution of the slipstream can be revealed by the method. The present work provides certain reference for both the design of propeller aircraft and the research on slipstream effect.