Circulation Retrieval of Simulated Wake Vortices Under Rainy Condition With a Side-Looking Scanning Radar

Abstract

The strength of a wake vortex can be well described by vortex circulation. In the area of aviation safety, it serves as a crucial parameter for assessing hazards caused by wake vortices, and its retrieval has attracted much attention in the past decades. Generally, radar is a very promising detection sensor for wake vortices generated under rainy condition where the scattering is mainly caused by the raindrops driven by wake vortices. This makes it possible to retrieve the circulation of wake vortices by sensing and quantifying the motion of these raindrops. This paper proposes the use of a side-looking radar, whose beam scans up and down alternatingly, for detecting wake vortices. In this method, raindrops that make major contribution to the total scattering are identified as characteristic-size raindrops, and their motion equation is established to connect their motion to the dynamics of wake vortices. When the velocity and acceleration of characteristic-size raindrops are well estimated from the Doppler spectra, the motion equation can be well solved by the nonlinear least squares method to yield the target parameter, circulation $\Gamma$ . At the same time, two other important parameters (vortex spacing $b_0$ and vortex-core height $y_0$ ) can be retrieved as well. Numerical simulation results verify good performance of the retrieval method.