PREDICTION OF SUPERCOOLED DROPLET IMPINGEMENT ON HELICOPTER ROTOR BLADES

摘要

In this paper, we describe the results of a numerical model of supercooled droplet, time-dependent trajectories and impingement on an isolated four-bladed rotor of a Bell 412 helicopter, in ideal hover flow condition. Rotor-fuselage aerodynamic interaction has been neglected in this exploratory research. The unsteady rotor flow field was obtained using CFD-FASTRAN solver and the Euler equations were used as the governing equations. This assumption significantly alleviates the grid density requirement near the surfaces and therefore greatly reduces the CPU time and memory needed for the simulation. The Chimera moving grid technique was applied to represent the blade rotation. Flow visualization was used to illustrate the prominent rotor downwash and the strong swirling flow field generated by the rotor blades. In the next step, supercooled droplets were inserted into the time-dependent, three-dimensional airflow and droplets trajectories were computed using a Lagrangian approach. The patterns of droplet impingement on rotating blades were examined for two droplet diameters. This is a first step towards predicting ice formation on rotating helicopter blades.