Self-Propulsion Performance Predictions for Polar Ships in Brash Ice Channels

Ice-strengthened polar ships play a vital role in enabling scientific research, resource exploration, tourism, and logistical support in the polar regions, particularly in the Arctic and Antarctic. These regions are characterized by extreme weather conditions, freezing temperatures, and the presence of sea ice, making navigation challenging and risky. Ice-strengthened ships are designed to withstand these harsh environments, and their importance lies in their ability to facilitate various activities while ensuring the safety of crew members and passengers. Indeed, the challenges posed by polar environments have long captivated the minds of engineers, beckoning them to develop innovative solutions that facilitate the safe and efficient navigation of ships through icy waters. In a pioneering study published in the esteemed peer-reviewed Journal Ocean Engineering, a team of researchers from the Jiangsu University of Science and Technology and Shanghai Jiao Tong University has made a significant stride in enhancing our understanding of self-propulsion performance for ice- strengthened ships in brash ice channels. Led by Professor Li Zhou and Dr. Chang Xie, Dr. Shifeng Ding, Dr. Renwei Liu, and Dr. Sijie Zheng, their study employed cutting-edge CFD-DEM coupling method to investigate into the intricate interplay between ship, propeller, and brash ice, ultimately illuminating the path forward for more accurate power evaluations and navigation guidance.

Ice-strengthened polar ships sailing through the challenging waters of the Northeast Route Sea require precise assessments of fuel consumption and engine power. Conventionally, two methods have been employed for evaluating engine power: the Finnish-Swedish Ice Class Rules (FSICR) and ice model tests. However, the latter’s exorbitant cost and the overestimation of power derived from FSICR make them less than optimal solutions. In this context, the development of a self-propulsion numerical tank based on Computational Fluid Dynamics (CFD) offers an efficient and cost-effective avenue for early-stage power evaluations and hull line development.

While research into the performance of polar ships in ice-covered waters predominantly focuses on ice resistance, there is a dearth of studies exploring numerical simulations of self-propulsion in brash ice channels. Prior work has concentrated on experimental research and numerical simulations in level ice conditions, employing methods such as the circumferential crack method. In contrast, the dynamics of ship-ice interaction in brash ice environments are complex due to the smaller ice sizes and the role of ship wake and resistance. Notably, the CFD-DEM coupling method, which combines the strengths of Computational Fluid Dynamics and the Discrete Element Method, emerges as a promising approach to comprehensively understand ship resistance and propulsion performance in brash ice channels considering the main factors as a whole.

The authors pioneered the use of the CFD-DEM coupling method to investigate self-propulsion performance in a brash ice channel. The methodology involves simulating the hydrodynamic performance of the propeller using CFD while calculating the ice load using DEM. The ship model, emulating real-world scenarios, is towed through the brash ice channel by a carriage with the assistance of a rotating propeller, closely mirroring ice tank test conditions. The simulation’s meticulous reproduction of both ship-ice and propeller-ice interaction processes highlights the method’s effectiveness.

The self-propulsion simulations under loaded and ballast conditions unveiled several key parameters including thrust, developed power, propulsion efficiency, and ice load on both hull and propeller. These parameters were then compared with model test data, yielding compelling results. The discrepancy between simulated and measured power was found to be within a commendable 8.5%. This validation underscores the robustness of the CFD-DEM coupling method in capturing the complex dynamics of self-propulsion in brash ice channels.

While the authors assumed unbreakable brash ice for simplicity, acknowledging the viscoelastic plastic nature of brash ice in reality is essential for further accuracy. Future research endeavors should explore the integration of a fracture model for brash ice and a viscoelastic plastic model, ensuring a closer alignment between simulation and real-world conditions. Additionally, refining the simulation to consider the complex interplay of ship wake and resistance, along with propeller-ice interaction, promises to enrich our understanding of self-propulsion in brash ice channels.

In conclusion, the authors findings heralds a significant advancement in our ability to predict self-propulsion performance for ice-strengthened polar ships navigating brash ice channels. By harnessing the power of the CFD-DEM coupling method, the team has unraveled the intricate interplay between ship, propeller, and ice, offering a technical tool for hull line development and navigation guidance. As we look to the future, the integration of more sophisticated models and comprehensive simulations holds the promise of even more accurate and insightful predictions, ultimately paving the way for safer and more efficient polar navigation.