Global Ice Loads on Arctic Drillships

This paper reports on an exercise to predict ice loads on Arctic drill ships using analytical, model ice basin test-based empirical, and numerical methods. An example drillship has been employed, and pack ice has been considered in theoretical and numerical analyses. Two analytical models for predicting the ice force have been employed for the head-on ice-ship interaction scenario with low ice concentration. One model is that the ice load is estimated as the average rate of momentum transfer between ice floes and ship hull. Another model is that the ice load is estimated based on the calculation of the motion and drag of ice floes as they move around the ship. In numerical modeling, a parametric study has been conducted to simulate different ice structure interaction scenarios using the Particle-In-Cell (PIC) method. Different parameters including ice thickness, ice concentration, ice movement velocity, and ice movement direction have been investigated in the interaction modeling. Based on numerical results, a formula for calculating the ice load has been developed to reflect the role of the pertinent parameters on expected ice forces and movements of the drillship. The comparison of results from all ice load models and numerical modeling shows a reasonable agreement. This study serves to help bound estimates of load and also provides insights into the different methods of global ice load prediction for this particular application.