Experimental Investigation of Ice Particle Impacts onto a Rigid Substrate

An experimental methodology has been designed for investigating ice particle impacts onto a rigid surface. Spherical ice particles with diameters ranging from 2.21mm to 3.18mm are projected onto a transparent glass target with a velocity of 37 m/s using a pneumatic gun. The impact dynamics are recorded in a view parallel and normal to the impact surface using highspeed video cameras and employing backlight shadowgraphy. While the initial size and speed of the impacting ice particle is extracted from the view parallel to the impact surface, the videos recorded in the normal view are analyzed using a novel approach. A Kalman filter tracking algorithm (KAFTA) allows recognition and tracking of each individual fragment generated during impact, as long it remains visible in the captured high speed video. This approach leads to highly accurate extraction of size and speed information for all fragments along their flight path. Information about the fragments shape and size in each snapshot is used for the total fragment volume estimation, leading to a more accurate results compared to classical volume computations assuming all fragments to be spherical. Using the tracking algorithm and fragment volume estimation method, size and velocity distributions of the fragment cloud are obtained.