Results of numerical simulations of growler impact tests

Abstract

Numerical simulations of a collision between free-floating growlers (1068 kg glacial ice mass) and a heavy apparatus (i.e. impact plate), similar to a ship bow, have been conducted using LS-Dyna™ software, which incorporates a full Navier–Stokes solver for the fluid component. The results compared favorably with actual data acquired during tests in IOT's Ice Tank using real growlers. The simulations were run on a Beowulf cluster consisting of 15 high-performance CPU's. The modeled volume, including the impactor, water and growler, was meshed using Ansys™ software and contained approximately one million elements. A prior set of non-impact simulations of a model tanker transiting in proximity to model bergy bits showed that at least this number of elements was required. In the results presented here the impactor was traveling at 2 m/s. A hard crushable foam material model was used for the growler in order to model previously observed ice behavior where the ice contact interface consists of a relatively intact hard zone of ice surrounded by softer pulverized ice. The simulation produced reasonable values for the load, pressure and impact duration values obtained in the actual growler experiments. Nominal pressure did not show a dependence on nominal contact area. It was notable that the same relatively simple hard crushable foam model used for the growler material properties was also successful in yielding reasonable results for simulations of full-scale impacts of a ship with bergy bits [Gagnon, R.E. and Derradji-Aouat, A., 2006. First Results of Numerical Simulations of Bergy Bit Collisions with the CCGS Terry Fox Icebreaker. Proceedings of IAHR 2006, Sapporo, Japan.]