Results from a Lagrangian-Lagrangian-based brownout simulation were compared to photogrammetric measurements of the evolving dust clouds generated by a helicopter during low altitude taxi-pass and approach-to-touchdown maneuvers. An inviscid-viscous method was used to represent the carrier phase from a combination of the rotor flow field (modeled as an inviscid flow using a free-vortex wake) and a semiempirical boundary layer flow model at the ground. The mobilization and initial uplift of dust particles were represented using semiempirical models for the effects of shear, unsteady pressures, and bombardment mechanisms, the subsequent particle motion being solved for by using a subset of the Basset-Boussinesq-Oseen equations. Although not all the measurements required for validation were available, the results showed good agreement to the measured evolution of the dust clouds. The results showed a significant sensitivity to the weight of the helicopter, as well as the initial flight path that it followed toward the ground. Small ambient winds were also found to affect both the initial development and the subsequent movement of the dust clouds. A particle quantity analysis showed that the majority of the smaller sized particles were uplifted by direct entrainment and bombardment ejection mechanisms, which when acting together rapidly increased the net quantity of suspended dust.
Predictions of brownout dust clouds compared to photogrammetry measurements
Journal of the American Helicopter Society ; 58 , 2 ; 022001/1-022001/18
2013
18 Seiten, 21 Bilder, 46 Quellen
Article (Journal)
English
Predictions of Brownout Dust Clouds Compared to Photogrammetry Measurements 022001
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