With the development of surface precision machining technology, as well as researches on lubrication and wear reduction, experimental and theoretical struggles on enhancing the surface lubrication properties using surface texturing technology has attracted widespread attention. Current research primarily focuses on preparing orderly grooves to improve their tribological behavior, with a particular emphasis on the influence of geometric parameters on friction performance. However, few researches have emphasized the impact of rough topographies of the machined surfaces on lubrication characteristics. This work uses the computational fluid dynamics (CFD) simulation method to establish lubrication models with roughed milling grooves, and their effects on the lubrication under water lubrication conditions were carefully examined. The study conducted simulations using variable parameters such as the depth ratio of knife marks (the ratio of lubricant film thickness to knife mark depth), width ratio (the ratio of single knife mark width to knife mark spacing), and the number of knife marks. When the number and width ratio of knife marks in the knife mark model are fixed, as the depth ratio of knife marks increases (H=0.6, 0.7, 0.8, 0.9, 1.0), the thickness of the lubricating film increases, and the bearing capacity increases. The lowest friction coefficient is obtained when the depth ratio H=1.0. When the depth ratio H is set to 1.0 and the number of knife marks is fixed, the friction coefficient shows a decreasing trend with the increase of the knife mark width ratio (W=0.8, 0.85, 0.9, 0.95), and reaches the lowest friction coefficient when the width ratio is W=0.95.Under shear friction conditions, the depth (H=1.0) and width (W=0.95) of the knife mark model are held constant, with the friction coefficient rising as the number of marks (n=2, 4, 6, 8, 10) increases.With the model unit size unchanged, the cross-sectional area of individual knife marks diminishes as the number of marks increases, leading to less pronounced fluid cavitation within each mark and consequently a smaller increase in flow field pressure at the microstructure's exit, ultimately reducing the lubricating film's total load-bearing capacity.Additionally, an increased number of knife marks results in a continuous vorticity distribution on the lower wall surface. This regular vorticity distribution on the lower wall enhances the intensity of the total vorticity on the upper surface, leading to an overall increase in vorticity. This results in energy dissipation, thereby increasing frictional resistance and reducing the dynamic pressure lubrication effect.Therefore, by judiciously selecting machining parameters, particularly adjusting the feed rate, feed speed, and tool selection during cutting, it is possible to influence the distribution pattern and surface roughness of the resulting knife marks, thereby optimizing their lubrication performance. These studies offer significant reference value for understanding milling machining and its design in industrial applications, providing a theoretical basis and experimental support for examining the impact on lubrication performance.

Knife marks; Roughness; Water lubrication; Dynamic pressure lubrication; hydrodynamics.