the effect of piston motion on the heat transfer is neglected, the rings do
not twist, the rings and skirt are fully engulfed in oil and there is no
cavitation, and also the conductive heat transfer in the oil film is
neglected [20]. Symmetric constraints are imposed in the axially
symmetric axis. That is, all of the displacements on the axially
symmetrical axis are set to zero in the radial direction.