Predictions of Rotor and Rotor/Airframe Configurational Effects on Brownout Dust Clouds

Abstract

Brownout dust cloud simulations were conducted for rotorcraft undergoing representative landing maneuvers, primarily to better understand the effects of different rotor placement and rotor/airframe configurations. A time-dependent free-vortex wake for the rotors and surface singularity method for the airframe were employed to represent the carrier phase of the flow. A coupling strategy for the free-vortex method was developed to include the effects of rotors operating at different rotational speeds, such as a tail rotor. For the dispersed phase of the flow, particle tracking was used to model the dust cloud based on solutions to a decoupled form of Basset–Boussinesq–Oseen equations appropriate to dilute gas/particle suspensions of low Reynolds number Stokes flow. The predicted flow fields near the ground and resulting dust clouds during the landing maneuvers were analyzed to better understand the nature and severity of their development and to examine differences produced by various rotor and airframe configurations. The formation of dust clouds was found to be partially sensitive to the transitional phase of the landing maneuver, when there were more significant aerodynamic interactions between the rotor wake and the fuselage.