Rotorcraft Brownout Advanced Understanding, Control, and Mitigation.

摘要

This MURI research concerns the problem of rotorcraft brownout, which is one of the military's most significant operational problems. Brownout occurs when loose, dusty material sitting on the ground is uplifted by the intense rotor wake as it interacts with the ground. The consequences of brownout is a degraded visual environment (DVE) for the pilot(s) as well as various motion cue anomalies, which poses a serious safety of flight issue. An interdisciplinary research program is being undertaken to advance the understanding of the fluid dynamic mechanisms responsible for brownout and DVE conditions, which is also leading toward a comprehensive predictive methodology for the problem. While classic mechanisms of sediment mobility under the action of near-wall flows have been documented in this research, several other unique mechanisms of sediment uplift arise because the unsteady, three-dimensional, and strongly vortical features of the rotor wake. The rotor blade tip vortices, in particular, are responsible for mobilizing and uplifting sediment particles from the ground. Several types of modeling approaches are being developed, ranging from those based on inviscid assumptions with semi-empirical models representing sediment mobility, to sophisticated two-phase computational fluid dynamic methods based more on first principles. Such computational approaches have also provided a rigorous basis to better understand the possibilities of developing brownout mitigation strategies from the perspective of both rotor design and flight path management. This final report summarizes the work done under this MURI research program, which has run from August 2008 to July 2014.