## 4 Simulation Results and Discussions  
In this paper, the Fluent software (ANSYS, Inc, Canonsburg, PA, USA) is employed to carry out the CFD calculation and the Tecplot code is used to do the post-processing. The operating conditions of the hydrostatic thrust bearing are identical for varied OLDRs. The CFD simulation results on the effects of various OLDRs for performance of the hydrostatic thrust bearing are calculated and discussed. The intrinsic characteristics of flow field and the macroscopic characteristics of the bearing are all analyzed in detail. Specifically, the pressure distributions, velocity profiles, and turbulent intensity along different lines are obtained with various OLDRs. The vortices, turbulent intensity, and pressure contours of corresponding sections and surfaces are presented. Furthermore, the load capacity, oil film stiffness, volume flow rate, and orifice flow resistance of the hydrostatic thrust bearing are compared with different OLDRs. The node pressure patterns along the line of \(c_{1}\)-\(c_{2}\) for different OLDRs are depicted in Figure 4. It can be found from Figure 4 that the oil pressure is equal to the inlet pressure at the beginning and then it decreases rapidly along the flow direction with almost the same declining rate for various OLDRs. The oil pressures of nodes from \(m_{1}\) to \(m_{7}\) are almost identical, indicating that there are few effects of OLDRs on the oil pressure of the orifice inlet. However, oil pressure presents different profiles in the orifice zone along the line of \(m\)-\(n\) with respect to different OLDRs. Specifically, the oil pressure reaches a minimum value and then increases slightly, and then decreases slightly, and then increases again along the flow direction for the OLDRs of 4 and 5, looking like a basin, and named a basin pressure profile in this paper. The oil pressure only increases slightly in the basin bottom for the OLDRs of 2 and 3. The oil pressure decreases to a minimum level and then increases rapidly along the flow direction for the OLDR of 1, presenting a pressure profile with no basin bottom. Only the pressure drop occurs in the orifice zone along the flow direction for the OLDRs of 0.25 and 0.5. It has almost the same pressure profile along the line of \(n\)-\(c_{2}\) with various OLDRs. Based on the aforementioned analysis, it can be found that the basin pressure effect is more obvious with increasing OLDRs in the orifice zone. That is to say, there is a pressure hold effect in the orifice zone and it will be more significant  
Figure 3: Partial computational meshes. with increasing OLDRs. In addition, the minimum oil pressure (\(p^{\prime}\)) in the orifice zone with respect to various OLDRs has the following relation:  
\[p^{\prime}{}_{1/d=0.25}>p^{\prime}{}_{1/d=0.5}>p^{\prime}{}_{1/d=5}>p^{\prime}{} _{1/d=1}>p^{\prime}{}_{1/d=4}>p^{\prime}{}_{1/d=3}>p^{\prime}{}_{1/d=2} \tag{1}\]  
The velocity magnitude patterns along the line of \(c_{1}\)-\(c_{2}\) for different OLDRs are depicted in Figure 5. It can be found from Figure 5 that the fluid velocity magnitude is almost identical at the oil inlet and then it increases rapidly along the flow direction with almost the same growth rate for various OLDRs. The fluid velocity magnitudes of nodes from \(m_{1}\) to \(m_{7}\) are almost identical, indicating that there are few effects of OLDRs on the fluid velocity magnitude of the orifice inlet. However, fluid velocity magnitude presents different profiles in the orifice zone along the line of \(m\)-\(n\) with respect to different OLDRs. Specifically, the fluid velocity magnitude reaches a maximum value and then decreases slightly, and when the fluid reaches the orifice outlet, the fluid velocity magnitude decreases rapidly along the flow direction for the OLDRs of 2, 3, 4, and 5, looking like an inverted basin, and named an inverted basin velocity magnitude profile in this paper.