Validation of Vortex Structures Detection Simplest Algorithms by the Induced Velocity Sensors in the Wind Tunnel Experiment

Аuthors

Krivoschapov A. A.

Central Aerohydrodynamic Institute named after N.E. Zhukovsky (TsAGI), 1, Zhukovsky str., Zhukovsky, Moscow Region, 140180, Russia

e-mail: alex5000.89@mail.ru

Abstract

The article addresses the task of vortex structures automatic detection in the airflow by the induced velocity sensors, which is of great importance for ensuring flight safety and developing warning systems for preventing an aircraft from entering wake vortices. The authors examined the simplest algorithms, based on determining the vortex center position through the analysis of induced flow velocity vectors at different spatial points. Validation was performed by the data from the wind tunnel experiment in the T-103 TsAGI facility, involving vortex wakes behind straight wings of various aspect ratios at an angle of attack of 10°. The testing relied on the measured velocity components obtained from the induced velocity sensors, as well as videogrammetry data for the actual vortex core positions determining. Analysis of the linear system of equations solution stability, which is fundamental for the search algorithms, through the condition number was performed, which allowed identifying the areas of higher sensitivity to the measurements errors. It was found that elimination of the points with small downwash values reduces the result dispersion and increases the search accuracy. In the case of the single vortex, localization error was not exceeding the value comparable with the span of the wing under study. In the case of the vortex wake, a systematic error caused by the vortex interaction in the cluster, was identified, which led to the result distortions particularly when the sensors were located farther from the core. The article demonstrates that application of the three sensors, which are not placed on the single straight line, allows the condition number reduction, and increase the algorithms stability. However, practical realization of this solution is limited by the structural specifics of the carrier. The cases, when the extra measurement cannot be ensured, require the data filtering by the condition number. The inference was drawn that the principle under consideration was effective only in the vicinity of the single vortex core, whereas its application for the complex wake structures is troublesome, and may lead tp the errors comparable to the inter-vortex distances. Elaboration of the algorithms based on the misclosure minimizing between the model and experimental downwash fields, which would allow correct account for the multi-vortex configurations, was denoted as a prospective trend. Such methods, including the gradient-based optimization approaches, show the potential for the onboard integration due to their computational efficiency and ability to operate with limited data. The obtained results confirm the meaningfulness of the optimal measurement configurations selection and detection algorithms adaptation to the real flight conditions.

Keywords:

vortex detection algorithms, induced velocity sensors, onboard vortex search system, validation based on a wind tunnel experiment

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