Study On The Radar Characteristics Of Aircraft Wake Vortices In Rainy Weather

The wake vortex is an inevitable phenomenon for an aircraft in flight. It has thecharacteristics of being very intense, stable, and large-scaled. Since the wake vortexmay pose serious impact to a following aircraft, the real-time detection of wake vortexhas become a key issue in the fields of aviation safety and so on. Radar is believed as amost potential approach for wake vortex detection in rainy weather condition, but thecorresponding radar scattering characteristics remain undiscovered. Under thisbackground, this thesis studies the radar characteristics of aircraft wake vortex in rainyweather, and the work can be classified into the following two aspects:The first aspect is about the dynamic characteristics of raindrops in wake vortices,which is the basis for the corresponding radar detection technology. Firstly, the RainDrop Size Distribution (DSD) and the terminal descend velocity models of rain dropsare briefly introduced, and some improvements are made on the existing models. Thenby combining the velocity model of wake vortex and the force analysis of raindrops, themotion equation of raindrops (a partial differential equation) is established, and then theRunge-Kutte method is adopted to solve this equation. Consequently, the velocity andspace distributions of raindrops in the wake vortex are obtained through numericalsimulations. Based on these distributions, the unique motion phenomena of raindropsinner and outer the vortex cores are abstracted, and the corresponding mechanisms areanalyzed. The research results will be useful to model radar characteristics of wakevortices in rainy weather as well as radar signal processing.The second aspect is about the Radar echo simulation of wake vertices in rainyweather. Based on the simplified models of raindrops, the scattering characteristics ofsingle raindrops at different sizes are analyzed, and the summation of them leads to theRCS of raindrops in a radar resolution cell. At the same time, the combination of thevelocities and scattering gives the reflectivity of the raindrops. Consequently, thecoherent video signal simulation is used to simulate Radar echo in different resolutioncell, and the Doppler spectrum of radar echo is obtained through signal processing. Thecomparison between the Doppler spectrum and radar reflection factor shows that theDoppler velocities extracted from the radar echoes fit well with the velocity spectrum ofraindrops. The research results could provide theoretical guidance to the wake detectionmethods of anti-stealth and aviation safety.The research on the unique motion of raindrops in wake vortices and the radarscattering characteristics in rainy weather could provide theoretical guidance to retrievethe circulation of wake vortex, and it is also very important to develop the detectiontechnology of aircraft wake vortex in humid atmosphere.