## 4 Simulation Results and Discussions
That is because the orifice-restricted hydrostatic thrust bearing is axisymmetric with respect to the central axis, and the fluid field of the orifice longitudinal section is not absolutely symmetric with respect to the node position of 58 mm. Besides, the orifices are located at the radius center line of the thrust bearing, and so the fluid field behaviors of the orifice section are nearly symmetric about the orifice central node. The influences of varying the OLDR on the load capacity, oil film stiffness, volume flow rate of the bearing, and the flow resistance of the orifice are shown in \[p^{\prime}{}_{1/d=0.25}>p^{\prime}{}_{1/d=0.5}>p^{\prime}{}_{1/d=5}>p^{\prime}{} _{1/d=1}>p^{\prime}{}_{1/d=4}>p^{\prime}{}_{1/d=3}>p^{\prime}{}_{1/d=2} \tag{1}\]0 It is clear from Figure 13a that the load capacity with an OLDR of 2 is larger than those of other OLDRs, and the load capacity for different OLDRs decreases as in the sequence of OLDRs of 2, 3, 1, 4, 5, 0.5, 0.25, which is consistent with the order of annular pressure. So, it confirms that annular pressures play a dominant role in the bearing capacity. In this paper, the oil film stiffness is calculated by the difference method (load variation divided by displacement variation). As can be found from Figure 13b, the OLDR of 0.25 corresponds to the maximum stiffness and the minimum stiffness is located at the OLDR of 1. The stiffness for different OLDRs decreases as in the sequence of OLDRs of 0.25, 5, 2, 4, 3, 0.5, 1. \[p^{\prime}{}_{1/d=0.25}>p^{\prime}{}_{1/d=0.5}>p^{\prime}{}_{1/d=5}>p^{\prime}{} _{1/d=1}>p^{\prime}{}_{1/d=4}>p^{\prime}{}_{1/d=3}>p^{\prime}{}_{1/d=2} \tag{1}\]1 Pressure distributions of wall \(S\) for various OLDRs. (**a**) \(l/d=0.25\); (**b**) \(l/d=0.5\); (**c**) \(l/d=1\); (**d**) \(l/d=2\); (**e**) \(l/d=3\); (**f**) \(l/d=4\); (**g**) \(l/d=5\). \[p^{\prime}{}_{1/d=0.25}>p^{\prime}{}_{1/d=0.5}>p^{\prime}{}_{1/d=5}>p^{\prime}{} _{1/d=1}>p^{\prime}{}_{1/d=4}>p^{\prime}{}_{1/d=3}>p^{\prime}{}_{1/d=2} \tag{1}\]2 Streamlines and turbulent intensities contours of orifice longitudinal sections for various OLDRs. (**a**) \(l/d=0.25\); (**b**) \(l/d=0.5\); (**c**) \(l/d=1\); (**d**) \(l/d=2\); (**e**) \(l/d=3\); (**f**) \(l/d=4\); (**g**) \(l/d=5\); (**h**) local enlarged view of I. The effects of varying the OLDR on the volume flow rate of the hydrostatic thrust bearing are shown in Figure 13c. It can be seen that the volume flow rate has the same variation pattern as the load capacity with various OLDRs. The volume flow rate of the hydrostatic thrust bearing with an OLDR of 2 is larger than those of other OLDRs, and the volume flow rate for different OLDRs decreases as in the sequence of OLDRs of 2, 3, 1, 4, 5, 0.5, 0.25. The orifice restrictor of the hydrostatic thrust bearing has an impedance effect on the fluid. The relationship among the flow rate, the pressure drop, and the flow resistance is similar to [PERSON]'s law in electricity [33]. Then, the flow resistance of the orifice can be induced as follows:  
\[p^{\prime}{}_{1/d=0.25}>p^{\prime}{}_{1/d=0.5}>p^{\prime}{}_{1/d=5}>p^{\prime}{} _{1/d=1}>p^{\prime}{}_{1/d=4}>p^{\prime}{}_{1/d=3}>p^{\prime}{}_{1/d=2} \tag{1}\]3  
where \(R_{\mathit{orifice}}\) is the flow resistance of an orifice, \(p_{m}\) and \(p_{n}\) are pressures of nodes \(m\) and \(n\), respectively, \(q\) is the flow rate of an orifice. Flow resistances of the orifice with different OLDRs are shown in Figure 13d. It can be found that the flow resistance increases with increasing OLDRs from 0.25 to 1, then it decreases slightly with increasing OLDRs from 1 to 3, and then it increases again with increasing OLDRs from 3 to 5, and thus does not always increase with the increasing OLDRs. The flow resistances of the orifice for different OLDRs decrease as in the sequence of OLDRs of 5, 1, 4, 2, 3, 0.5, 0.25.