The behavior of the hollow oil droplets impinging on the rough surface often take place in the oil-gas lubricating system

which will affect the quality of the oil film formation on the surface of the friction pairs. The coupled level set and volume-of-fraction (CLSVOF) method is used to simulate this behavior. The formation mechanism of the central jet and the distribution of air entrainment are analyzed. And the effects of grooved width

grooved depth and impact position on the oil droplet spreading process are investigated. The results show that the central jet and air entrainment can be formed after the hollow oil droplet rectangular groove surface. The formation of the central jet originates from the velocity vortex at the bottom of impacting on the bubble. The position of air entrainment in the grooves is influenced by the spreading velocity of the hollow oil droplet. When the dimensionless grooved width Ag is less than 0.2 or equal to 0.4

the spreading coefficient of vertical grooves Dx of the hollow oil droplet is approximately same. However

when the dimensionless grooved width is equal to 0.3

the spreading coefficient of vertical grooves Dx increases rapidly in the later period of movement due to the formation of a neck jet on the grooved surface. In addition

the spreading coefficient of parallel grooves Dz increases with the increase of grooved width. The spreading height coefficient Dy of the oil droplet is consistent on each surface and is not affected by the grooved width. When the dimensionless grooved depth Hg ≤ 0.2

the spreading coefficient of vertical groove Dx decreases with the depth of groove increasing. When the dimensionless grooved depth Hg>0.2

the spreading coefficient of vertical grooves Dx is almost equal. However

with the increase of grooved depth

the spreading coefficient of parallel grooves Dz is decreased. The spreading height coefficient Dy of the hollow oil droplet decreases with the increase of the grooved depth

and the increase of the grooved depth can prevent the formation of the central jet. The effects of the impact position on the distribution of air entrainment are significant

while the movement of hollow oil droplet plays a negligible role in them.