Investigating Errors of Wake Vortex Retrievals Using High Fidelity Lidar Simulations

Abstract

Wake vortex characterization algorithms for Light Detection and Ranging (lidar) measurements are vital for airport operation studies considering both efficiency of aircraft throughput and the related safety issue. To date the operational accuracy of algorithms such as the Radial Velocity (RV) method, particularly in turbulent atmosphere, has not been quantified thoroughly. In real lidar scans, the true flow field and the characteristics of the contained coherent structures, such as wake vortices, are unknown. Thus, the error of algorithms such as the RV method has not yet been considered beyond theoretical estimations. In this work we tackle the unavailability of a ground-truth by simulating virtual lidar instruments employing high fidelity Large Eddy Simulations (LES) of a landing aircraft. Within the numerical simulations the characteristics of the wake vortices are fully known, so that the accuracy of algorithms such as the RV method can be investigated and quantified. Virtual lidar scans generated by our proposed LES Lidar Simulator (LLS) focus on accurately representing the filtering effect of real lidar via a range gate weighing function. Comparisons to real lidar measurements and the simulated wake of the LES suggest that first accuracy estimations of the RV method can already be performed with the present LLS version. We observe that theoretical RV method characterization errors are significant underestimations, particularly the strength of vortices appears to be overestimated. These results manifest the necessity to investigate errors inherent to wake vortex characterization algorithms from lidar measurements also in further atmospheric conditions and aircraft landing scenarios.