Low-viscosity hydrodynamic fluid film generation behaviors and frictional performance of spiral-groove textured surface considering roughness

In this study, low-viscosity hydrodynamic fluid film generation behaviors and frictional properties of spiral-groove textured surface considering roughness were investigated theoretically and experimentally. A lubrication model incorporating the average Reynolds equation, the Greenwood–Tripp asperity contact model, and the Jakobsson–Floberg–Olsson cavitation boundary was developed to analyze the influence of critical operational conditions and geometric parameters on hydrodynamic lubrication behaviors and frictional properties, which can support the identification of lubrication regimes and the optimization of spiral-groove textures under water lubrication. Theoretical results revealed that the transition from mixed to full hydrodynamic lubrication is highly dependent on rotational speed, surface roughness, and applied load. Optimization of groove depth, spiral angle, and groove-to-weir ratio could promote the formation of stable film and friction reduction under low-viscosity lubrication, where challenges such as reduced film thickness, cavitation, and roughness effects need to be carefully considered. An experimental device to investigate the fluid film generation behaviors and a specific calibration procedure to determine fluid film thickness were developed. Experimental results further indicate that clockwise rotation facilitates fluid pumping and increases film thickness, while a larger number of grooves effectively enhances the hydrodynamic effect and lowers the friction coefficient. Combined with a rotating-type tribometer, the theoretical prediction reliability of fluid film thickness and frictional performance variation laws were verified accordingly.