Material Properties of Granular Ice Layers Characterized Using a Rigid-Body-Penetration Method: Experiments and Modeling

Accretion and shedding of ice layers is a serious problem for various engineering applications. In particular, ice layers growing due to ice crystal impingement on warm parts of an aircraft jet engine pose a severe hazard since they seriously affect safe operation of an aircraft. The material properties, and in the first place the strength of an ice layer, are crucial for the mechanisms leading to, and taking place during, both accretion and shedding of an ice layer. In the present study, the apparent yield strength of dry granular ice layers is examined employing a novel rigid-body-penetration approach. Dynamic projectile penetration into granular ice layers of varying porosity and ice grain size is experimentally investigated for different projectile impact velocities using a high-speed video system and post-processing of the captured video data. The obtained data for the total penetration depth of the projectile is used to calculate the apparent yield strength of the ice layer based on theoretical modeling of the projectile dynamics during penetration. Finally, the experimental method and theoretical modeling employed in the present study turn out as a promising way for the characterization of ice layers under varying circumstances such as generic wind tunnel icing experiments, enabling correlation of phenomenological observations of ice accretion and shedding to the material properties of the ice layer.