CFD analysis of cavitated flow in multi-groove water lubricated bearings with partial and full slip effects

Abstract

• CFD analysis was performed on a 8-groove water lubricated bearings, considering wall slip effects and cavitation phenomena across speeds up to 6000 RPM and slip magnitudes of 2 %–8 %. • Hydrodynamic film pressure builds in land areas from flow patterns, while grooves feed lubricant at lower pressure. Higher speeds raise load capacity but also increase cavitation risk. • Slip conditions boost pressure by reducing wall shear but also increase negative pressures and cavitation risk, stressing the need for balanced WLB design. • Flow visualization highlights intricate vortex behavior within the grooves, with their size and position being highly influenced by both slip conditions and journal speed. With increasing emphasis on green tribology and environmentally sustainable technologies, water-lubricated bearings (WLBs) have gained prominence in marine stern tube applications. This study introduces a CFD-based investigation of a multi-groove WLB, incorporating both slip flow effects and cavitation modelling at varying speeds. A realistic 8-groove bearing geometry, modelled after a commercially available V-groove stern tube bearing was analyzed across a wide journal speed range (2000–6000 RPM) and slip ratios (2 %–8 %). The study provides new insights into the influence of slip flow on hydrodynamic pressure distribution and its role in intensifying cavitation, particularly at high rotational speeds. Notably, the interplay between groove-induced inertia and slip was found to govern pressure development and vortex formation within the lubricant film. At mid-range speeds (4000 RPM), slip influence was minimal (<1.3 %), while at higher speeds, pressure increased by over 140 %, amplifying load capacity but also causing cavitation pressures as low as –76.8 kPa. However, at higher slip values and speeds, slip flow contributed to both increased pressure and a greater risk of cavitation. Flow visualization reveals complex vortex structures within the grooves, with their size and location strongly affected by slip conditions and journal speed. This study distinctively illustrates the intricate relationship between slip-induced pressure augmentation and cavitation severity in grooved water-lubricated bearings. The findings emphasize a critical trade-off between improved hydrodynamic performance and increased cavitation risk, offering valuable insights for the design and optimization of marine bearing systems operating under varying conditions.

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