Aircraft Wake-Vortex Evolution in Ground Proximity: Analysis and Parameterization

Abstract

Field measurement data of 282 wake vortex pairs and respective environmental conditions acquired at Frankfurt Airport by means of lidar, Sodar/RASS, and ultrasonic anemometer are used to analyze wake vortex behavior in ground proximity. Exceptional cases with strong rebounds caused by detached shear layers and obstacles are introduced and estimates of the time needed to clear the runway from wake vortices by advection are provided. The impact of turbulence and crosswind on wake vortex decay proves to be weak, whereas already light crosswind turns out to be sufficient to cause pronounced asymmetric rebound characteristics. Based on the analyses vortex decay and rebound characteristics are parameterized and implemented into the probabilistic two-phase aircraft wake-vortex model. Deterministic and probabilistic prediction skill of the enhanced vortex model are assessed. Comparison to wake predictions out of ground effect indicates that in ground effect (i) the rapid-decay phase progresses slower, (ii) wake vortex evolution can be predicted with improved accuracy, and (iii) fair prediction skill requires only limited environmental data.