This study investigates the hydrodynamic response of polar transport ships under ice-propeller-rudder multi-body interactions in brash ice channels. The study develops a numerical ice tank and a discrete element model for brash ice using a coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) integrated with overset grid technology. The research analyzes the self-propulsion characteristics of ships navigating in brash ice channels. The reliability of the Discrete Element Method (DEM) is validated through quantitative comparisons between numerical results and experimental data for ice-induced resistance. The analysis examines the influence of propeller rotational speed on the hydrodynamic performance of the propeller-rudder system under different loading conditions, considering both ice-free and ice-covered environments. Results indicate that the propeller rotational speed required to achieve the self-propulsion point at scantling draft condition is higher than that required at design draft condition. Furthermore, the study compares the force characteristics of the propeller-rudder system in both time and frequency domains, contrasting environments with and without brash ice. These findings provide valuable insights for predicting ice loads and ensuring navigational safety of ships in ice-covered waters.