云雾、雨中飞机尾流雷达特性研究和空气动力学特征反演技术

When flying in the air, the aircraft generates a pair of counter-rotating intensive vortices due to the pressure difference between the upper and lower surfaces of the wing. The aircraft wake vortex has impacts on the aircraft entering into it and the Earth's heat radiation balance. The wake vortex detection technology is one of the emerging research topics in the fields such as aviation safety and atmospheric science. Radar and Lidar are two effective wake detection sensors. In cloudy, rainy and snow conditions, the effective detection range of Lidar is significantly reduced, however, Radar has a better detection performance due to the enhanced backscattering from cloud droplets, raindrops and snowflakes. On the background of aviation safety, the wake vortices in cloud and rain are the research targets in this project. The roadmap of induction-inversion is adopted here. The wake vortex radar echo modeling will be achieved by the analysis of the velocity and spatial distribution of cloud droplets and raindrops in wake vortices. On this basis, the radar signal processing technology will be studied, in order to reveal the intrinsic relationships between wake vortex radar characteristics and the characteristics of wake vortex velocity distribution, vortex separation and descent velocity and achieve the retrieval of wake vortex aerodynamic characteristics based on the radar characteristics. The achievements in this project will be significantly important for the assessment of wake vortex hazards, improvement of aviation safety and reduction of the rate of flight delays.

飞机尾流是飞机飞行时因机翼上下表面压力差而在机翼后方产生的一对反向旋转的强烈涡旋。尾流是航空安全的重要影响因素，并会对地球热辐射平衡产生影响，其探测技术是航空安全、大气科学等领域的新兴研究方向。雷达和激光雷达是两种有效的尾流探测传感器。在云雾、降雨、降雪条件下，激光雷达的作用距离会显著降低，而雷达却会因云雾滴、雨滴、雪花的散射增强作用而具有更好的探测性能。 本项目以航空安全为背景，以云雾、降雨条件下的飞机尾流为研究对象，采取先归纳再反演的技术路线，分析尾流中云雾滴、雨滴的速度、空间分布等特性，实现云雾、降雨中尾流雷达回波特性建模。进而研究云雾、雨中尾流的雷达回波处理技术和雷达特性，揭示尾流雷达特性与尾流速度分布、涡间距、飘降速度等特征之间的内在关系，实现基于尾流雷达特性的空气动力学特征反演技术突破。研究成果对评估尾流危害程度、提高航空气象预警及安全性能、降低航班晚点率具有重要意义。

从大气科学的角度上看，与龙卷风、微暴、锋面等自然大气物理现象相比，飞机尾流是一类小尺度的大气物理现象。从雷达目标特性角度看，飞机尾流是一类特殊的电特大尺寸（尾流尺度远远大于雷达波长）目标，与常规的雷达目标相比，飞机尾流具有跨距离分辨单元、跨角度分辨单元和跨多普勒分辨单元等属性。本项目将飞机尾流作为研究对象，突破了云雾、降雨条件下飞机尾流雷达特性建模和雷达信号处理技术难题，在此基础上，提出了有效的基于雷达探测的尾流速度分布、环量、飘降速度、环量衰减速度等空气动力学特征反演方法，为云雾、降雨条件下飞机尾流监视提供有效的技术途径。