Multi-Phase Analysis of Oil-Air Cavitation and Its Impact on Heat Generation and Wear in High-Speed Automatic Transmission Lubrication

Automatic transmissions operate under high-speed and high-load conditions, where effective lubrication and cooling are critical for durability and efficiency. One of the key challenges in such systems is oil-air cavitation, which arises due to rapid pressure fluctuations and shear forces within the Automatic Transmission Fluid (ATF). This phenomenon leads to bubble formation and collapse, generating localized thermal spikes, increasing viscous dissipation, and accelerating component wear. This study employs Computational Fluid Dynamics (CFD) simulations using ANSYS Fluent to investigate cavitation effects in the automatic transmissions. A Volume of Fluid (VOF) multiphase model is used to simulate oil-air interactions, while the Schnerr-Sauer cavitation model captures bubble dynamics under varying operating conditions. Key parameters, including gear rotational velocity, ATF viscosity-temperature characteristics, oil jet injection angles, and pressure gradients, are evaluated to quantify their impact on localized heat generation and gear surface degradation. Simulation results reveal cavitation-induced hotspots, fluid film breakdown risks, and gear surface fatigue due to microbubble collapse. Furthermore, the study explores additive-based ATF modifications and optimized lubrication strategies to mitigate cavitation effects. The findings provide a framework for improving ATF formulations, optimizing lubrication architecture, and enhancing transmission reliability in modern high-performance drivetrains. This research contributes to the design of next-generation transmission lubrication systems, ensuring superior thermal management and wear resistance in advanced automatic transmissions.