With the rapid development of the new energy vehicle market, the demand for efficient, low-noise, low-energy consumption, high-strength, and durable gear transmission systems is continuously increasing. Therefore, it has become imperative to conduct in-depth research into the fluid heat transfer and lubrication dynamics within gearboxes. In gear systems, the interaction between fluids and solids leads to complex nonlinear heat transfer characteristics between gears and lubricants, making the development and resolution of gearbox thermodynamic models highly challenging. This paper proposes a gear lubrication heat transfer dynamics model based on LBM-LES coupling to study the dynamic laws and heat transfer characteristics of the gear lubrication process. The research results indicate that the interaction between gears and the intense shear effects caused by high speeds generate vortices, which are particularly pronounced on larger gears. The fluid mixing effect in these high vortex regions is better, achieving a more uniform heat dissipation effect. Furthermore, the flow characteristics of the lubricant are closely related to speed and temperature. Under high-temperature conditions (such as 100 °C), the diffusion range of the lubricant increases, forming a wider oil film, but its viscosity significantly decreases, leading to greater stirring losses. By optimizing the selection of lubricants and stirring parameters, the efficiency and reliability of the gear transmission system can be further improved, extending its service life. This study provides a comprehensive analytical framework for the thermodynamic characteristics of multi-stage transmission systems, clarifying the heat transfer mechanisms within the gearbox and offering new insights and theoretical foundations for future research and engineering applications in this field.

Static mixers have been widely used in marine research fields, such as marine control systems, ballast water treatment systems, and seawater desalination, due to their high efficiency, low energy consumption, and broad applicability. However, the turbulent mixing process and fluid–wall interactions involving complex structures make the mixing transport characteristics of static mixers complex and nonlinear, which affect the mixing efficiency and stability of the fluid control device. Here, the modeling and design optimization of the two-phase flow mixing and transport dynamics of a static mixer face many challenges. This paper proposes a modeling and problem-solving method for the two-phase flow transport dynamics of static mixers, based on the lattice Boltzmann method (LBM) and large eddy simulation (LES). The characteristics of the two-phase flow mixing dynamics and design optimization strategies for complex component structures are analyzed. First, a two-phase flow transport dynamics model for static mixers is set up, based on the LBM and a multiple-relaxation-time wall-adapting local eddy (MRT-WALE) vortex viscosity coupling model. Using octree lattice block refinement technology, the interaction mechanism between the fluid and the wall during the mixing process is explored. Then, the design optimization strategies for the flow field are analyzed under different flow rates and mixing element configurations to improve the mixing efficiency and stability. The research results indicate that the proposed modeling and problem-solving methods can reveal the dynamic evolution process of mixed-flow fields. Blade components are the main driving force behind the increased turbulent kinetic energy and induced vortex formation, enhancing the macroscopic mixing effect. Moreover, variations in the flow velocity and blade angles are important factors affecting the system pressure drop. If the inlet velocity is 3 m/s and the blade angle is 90°, the static mixer exhibits optimized overall performance. The quantitative analysis shows that increasing the blade angle from 80° to 100° reduces the pressure drop by approximately 44%, while raising the inlet velocity from 3 m/s to 15 m/s lowers the outlet COV value by about 70%, indicating enhanced mixing uniformity. These findings confirm that an inlet velocity of 3 m/s combined with a 90° blade angle provides an optimal trade-off between mixing performance and energy efficiency.