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Activity title

Unsteady Aerodynamic Response of Rigid Wings in Gust Encounters

Activity Reference

AVT-282

Panel

Applied Vehicle Technology

Security Classification

NATO UNCLASSIFIED

Status

Active

Activity type

RTG

Start date

2017

End date

2019

Keywords

dynamic stall, flow control, gusts, indicial flows, unsteady aerodynamics, Urban winds

Background

NATO-wide, there is a critical need to evolve tactical intelligence/reconnaissance/surveillance airborne platform capabilities, especially at the level of Micro Air Vehicles (MAVs) across a broad range of vehicle sizes, flight speeds and operational altitudes. This includes both maneuverability and flight agility improvement for small aircraft operating in urban environments, and at the opposite extreme, the robustness of high aspect ratio aircraft to high-altitude atmospheric disturbances. For smaller aircraft, the problem becomes one of how to robustly place sensors on target. AVT-101, 149, 182, 184, 202, and 239 have been pursuing flight-sciences for small and micro unmanned air vehicles, in the study of steady and unsteady aerodynamics, technology state of the art identification, and flight-characterization methods. Results of these groups have contributed significantly to our understanding of the relevant aerodynamics and flight dynamics. Nevertheless, current vehicle designs emphasize cruise and loiter efficiency, not maneuvering or robust unsteady response. While any solution to improve maneuverability must not be detrimental to cruise performance, better vehicle handling in a gusty environment will greatly enhance the operational envelope of these vehicles. We are now ready to extend the current state-of-the-art to unsteady flight environments to support the goal of robust flight article performance where wind gusts are of the same order of magnitude as the vehicle’s flight speed, and where disturbance-rejection may be achieved via closed-loop flow control.

Objectives

Building on AVT-149 and AVT-202, the group will experimentally, computationally and analytically study canonical problems in flow separation and aerodynamic force/moment history, now with a focus on predicting aerodynamic response and recovery via reduced-order models, with the goal of mitigating disturbance-effects in highly unsteady transient flows (e.g., gust encounters) at the relevant flow time scales.

Topics

The group will study the fluid mechanics and fluid-structure interaction of canonical and flight-relevant wing shapes executing various motions in 3 degrees of freedom in both quiescent flows and gusty/unsteady environments. Special cases include extreme maneuvers (e.g., steep climbs, dives, turns, perching, flapping) and gust encounters relevant to urban wind fields and air wakes.

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