2024

Juttula, Harri; Suopajärvi, Jussi; Molkoselkä, Eero; Kaikkonen, Ville; Mäkynen, Anssi

An 85 meters long steel was installed on top of the Olos fell in northern Finland to observe both ice shedding due to controlled impacts and rime ice growth due to cloud droplets. A custom ice dropper was designed and installed on the cable. Ice dropper design was based on sudden release of additional tension due to forced bending of the cable. A cloud droplet sensor (ICEMET) and weather station were installed on site to monitor the liquid water content (LWC), temperature and wind conditions during the field tests. Additionally, a commercial load sensor was attached to the cable and a camera was installed to provide live feed from the weather and ice conditions on the site. A series of remotely operated tests with the ice dropper were performed during the test period when significant amount of ice was observed on the cable. The ice dropper provided mixed results with some events removing successfully up to 30 kg of ice with clear visual evidence. Change in the ice mass was estimated by using a linear regression model based on a physical simulation of the cable created with COMSOL Multiphysics software. Simulation model of the cable related the cable tension to the physical properties of the cable, point load from the ice dropper, additional ice load and thermal expansion and drag forces due to temperature and wind. A total of eight ice dropper tests were analysed with the numerical model. Between two individual ice dropping events ICEMET detected a long period of up to 0.2 g/m3 liquid water content in the air which was visually confirmed by poor visibility in the surveillance camera images and increase of cable tension and diameter of ice layer.