The moving particle semi-implicit (MPS) method has been used in a wide range of industrial fields with the free surface. Many machines use oil for lubrication as well as cooling. In this study, stirred fluid flow of various oil types with rotating cam-shafts was calculated by using the MPS method. Moreover, experiments were conducted in order to validate the calculation results by comparing the torque values. When the oil viscosity is 30 cs or lower than 30 cs, the calculated torques agree well

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... with those of the experiment. When the oil viscosity is larger than 30 cs, the calculated torques are lower than those of the experiment. This is due to the involvement of small air bubbles. The air bubbles are retained for a long time when the oil viscosity is high, which increases the oil surface and eventually causes a higher torque. This phenomenon is not calculated because the air bubbles are not modeled in this study. In the case when the oil viscosity is 30 cs, the calculation results of the torque values were in good agreement with those of the experimental results. The calculation results show convergence with respect to the particle size.