Droplet deformation and trajectory without interferences in the incoming airfoil shoulder region

Abstract

A new experimental campaign has been conducted in the shoulder region of an incoming airfoil of chord 1050 mm, where droplets are separated enough to neglect interferences between them. Droplets of three sizes (500, 950, and 1250 μmof radius) were allowed to fall in the path of an incoming airfoil while shadowgraph images were recorded by a high-speed video camera at 40,000 fps. The airfoil model was placed at the end of a rotating arm and moved at four velocities (30, 40, 50, and 60 m∕s). Three different regions of the shoulder were tested. Droplet deformation and trajectories are presented. Droplets evolve as a conjunction of two half-oblate spheroids that tilt as the model approaches. The tilting is larger in the higher regions of the shoulder. The trajectory model derived for droplet in the stagnation line of a moving airfoil has been formally derived for the shoulder region and applied to the experimental data, showing very good agreement being the mean discrepancy less than 4% for the trajectory and 10% for the deformation.