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Roisman, Ilia
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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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MUSIC-Haic: 3D Multidisciplinary Tools for the Simulation of In-Flight Icing due to High Altitude Ice Crystals

Darmstadt University of Technology-Ilia Roisman, Cameron Tropea
General Electric Aviation-Paolo Vanacore
Published 2019-06-10 by SAE International in United States
Icing is a major hazard for aviation safety. Over the last decades an additional risk has been identified when flying in clouds with high concentrations of ice-crystals where ice accretion may occur on warm parts of the engine core, resulting in engine incidents such as loss of engine thrust, strong vibrations, blade damage, or even the inability to restart engines. Performing physical engine tests in icing wind tunnels is extremely challenging, therefore, the need for numerical simulation tools able to accurately predict ICI (Ice Crystal Icing) is urgent and paramount for the aeronautics industry, especially regarding the development of new generation engines (UHBR = Ultra High Bypass Ratio, CROR = Counter rotating Open Rotor, ATP = Advanced Turboprop) for which analysis methods largely based on previous engines experience may be less and less applicable. The European research project MUSIC-haic has been conceived to fill this gap and has started in September 2018. MUSIC-haic brings together the main European research institutions working on icing modelling as well as engine manufacturers and aircraft manufacturers. The project will…
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Impact of Supercooled Liquid Drops onto Cold Solid Substrates

Technical Univ. of Darmstadt-Hai Li, Ilia Roisman, Cameron Tropea
Published 2015-06-15 by SAE International in United States
Airframe icing caused by supercooled large droplets (SLD) has been identified as a severe hazard in aviation. This study presents an investigation of impact of a supercooled drop onto superhydrophobic and partially wettable substrates. Drop impact, spreading and rebound were observed using a high-speed video system. The maximum spreading diameter of an impacting drop on partially wettable surfaces was measured. The temperature effect on this parameter was only minor for a wide range of the drop and substrate temperatures. However solidification hindered receding when both the drop and substrate temperatures were below 0°C. The minimum receding diameter and the speed of ice accretion on the substrate were measured for various wall and drop temperatures. The two parameters increased almost linearly with the decrease of the wall temperature, but eventually leveled off beyond a certain substrate temperature. The speed of ice accretion on the substrate was significantly higher than the growth rate of free ice dendrites at a certain supercooling. These disparities are attributed to formation of multiple initial nucleation sites and the liquid flow. These…
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Surface Energy Influence on Supercooled Water Crystallization: A Computational Study

TAKATA AG, EMEA New Devices Engineering-Antonio Criscione
Technical Univ. of Darmstadt-Suad Jakirlic, Ilia Roisman, Cameron Tropea
Published 2015-06-15 by SAE International in United States
Numerical experiments have been presently conducted aiming at studying the influence of the surface energy on the crystallization process of supercooled water in terms of the supercooling degrees. The mathematical model consists primarily of the equation governing the thermal energy field solved independently in both phases in accordance with the two-scalar approach by utilizing the Stefan condition at the interface to couple both temperature fields. The computational algorithm relying on the level-set method for solid-liquid interface capturing has been appropriately upgraded aiming at accuracy level increase with respect to the discretization of the thermal energy equation and the normal-to-interface derivative of the temperature field. The model describes the freezing mechanism under supercooled conditions, relying on the physical and mathematical description of the two-phase moving-boundary approach. The relevant numerical algorithm is implemented into the open source software OpenFOAM®. The results obtained illustrate the stabilizing effect of the surface energy compared to the level of supercooling. The effect of the anisotropy of the interfacial energy on the ice nucleus growth, resulting in a six-fold crystal shape, is…
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