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

Technical University of Darmstadt-Markus Schremb, Kenan Malicevic, Louis Reitter, Ilia Roisman, Cameron Tropea
Published 2019-06-10 by SAE International in United States
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…
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Ice Nucleation in the Presence of Electric Fields: An Experimental Study

TU Darmstadt, High-Voltage Laboratories-Jens-Michael Löwe, Volker Hinrichsen
TU Darmstadt, SLA-Markus Schremb, Cameron Tropea
Published 2019-06-10 by SAE International in United States
In the present study, ice nucleation in sessile water drops during continuous cool down is studied experimentally under the impact of a constant electric field, to determine its influence on heterogeneous nucleation. The experimental setup enables simultaneous observation of multiple drops under well-defined conditions with and without an electric field and at temperatures down to -40 °C. A single experimental run contains 40 drops exposed to the same conditions. Drops with a well-defined size are produced employing a drop-on-demand drop generator. Based on multiple experimental runs using the same drops, the nucleation behavior is analyzed using statistical methods to determine the drop survival curves and nucleation site densities for varying conditions. Besides the influence of the electric field, the influence of different drop ensembles is investigated for a constant cooling rate of 5 K/min. A comparison of the experiments with and without an electric field is used to elaborate its influence on heterogeneous ice nucleation.
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