Muti-Objective Optimization of Hydrodynamic Journal Bearings for Wind Turbine Gearboxes: A CFD-FEM Coupled Framework for Enhanced Performance, Durability and Sustainability

This study presents a comprehensive multi-objective optimization framework for the design of hydrodynamic journal bearings in wind turbine gearboxes, aimed at minimizing maximum hydrodynamic pressure and maximizing load-carrying capacity to enhance durability and operational reliability. By integrating Fluid-Structure Interaction (FSI) analysis through coupled Computational Fluid Dynamics (CFD) and Finite Element Method (FEM) simulations within ANSYS Workbench, the framework captures the complex interplay between fluid film behavior and structural deformation under real operating conditions. The optimization process was implemented via the ModeFrontier platform, evaluating 100 design configurations that varied key geometric and operational parameters such as L/D ratio, radial clearance, and rotational speed. The resulting Pareto front revealed a nonlinear trade-off between pressure and load capacity. This is because the relationships between variables are nonlinear due to several factors: the cubic dependence of film thickness on pressure, the nonlinear viscous behavior of the fluid under load, the structural elastic deformation coupled with the pressure gradient, and the geometric interactions of the length-to-diameter ratio (L/D) and clearance. The best-performing designs achieved up to a 38% reduction in maximum pressure and a 47% increase in load-carrying capacity compared to baseline configurations, while also reducing structural stress concentrations and deformation. Although thermal and acoustic effects were not explicitly modeled, the optimized geometries are expected to provide indirect improvements in temperature control, vibration damping, and noise reduction—critical factors in offshore and remote wind turbine applications. Sensitivity analysis confirmed the dominant influence of clearance and L/D ratio on bearing performance, reinforcing the need for precise design control in renewable energy solutions. These results demonstrate the potential of hydrodynamic journal bearings to outperform conventional roller bearings in high-speed shaft applications by offering higher load support, longer fatigue life, and lower maintenance demands. The study establishes a solid foundation for further research and experimental validation, supporting the broader adoption of advanced bearing technologies to improve the efficiency, sustainability, and economic competitiveness of wind energy systems.