Smoothed particle hydrodynamics modeling of brash ice

Abstract

In the context of arctic navigation through man-made channels, brash ice is a very common type of ice through which ships navigate, that basically consists in several layers of rigid ice pieces floating in water, thus, affecting its resistance and behavior. The high complexity of the prediction of these impacts in terms of the physical description makes it a non-tackled problem in the present time, although some simplified approaches have been proposed and its mechanical properties have been studied up to some extent. The objective of this work is to study, propose and implement a suitable numerical model for brash ice simulations based on the available experimental data and previous work on ice dynamics. Four options are briefly analyzed, a full SPH approach for single-phase granular flows and for two-phase mediums, a coupling method between SPH and DEM and a physical based method. The SPH approach for single-phase granular flows is then selected and a differential equation for brash ice is proposed with its respective SPH discretized form. An SPH open-source code is selected after a detailed discussion of the different options to accomplish this task based on several variables that were highly important in terms of future possible developments and the scope this work. For the implementation a detailed description of this tool and of the modifications is provided. This study focuses on two main modifications, a new rheological implementation and a new buoyancy condition. A convergence study in time is performed, to assess reliability and to pick the appropriate parameters for the simulation, with these parameters a sensitivity analysis is performed checking the influences of the different rheological variables in the resistance force, velocity fields and pressure fields. Finally the work will be compared with experimental data obtained from a cylinder resistance test conducted in the HSVA ice tank facilities, the comparison will focus mainly on the resistance measured on the experiment and also will provide a visual comparison of the velocity fields and the overall behavior of the medium. The report ends with conclusions on the new approach here proposed and several suggestions for further development