## 5 Calculations in a Universal CFD Program
### Determination of Pressure Distribution and Reaction Forces  
Pressure distribution calculations were carried out for a fixed journal position, defined by two parameters: the eccentricity (ECC) and the angle (Angle) determined by the positive half-axis X and the ray passing through the centers of the sleeve and journal (Figure 1). During the analysis and in the results presented, the dimensionless eccentricity \(\varepsilon\) was used, i.e., the eccentricity expressed in micrometers relative to the nominal value of the radial clearance (35 \(\upmu\)m), also expressed in micrometers. An important aspect of calculating the load capacities of the bearings is the discretization of the model. In the calculations discussed herein, second-order (quadratic) finite volumes were used to discretize the gas domain, with each edge having an internode. Splitting the model along the plane of symmetry allowed for a reduction in the size of the problem and a more accurate discretization. To select the optimal method for discretizing the model, a series of calculations was performed to test the effects of the number of finite volumes and the density of the numerical grid in individual directions on the accuracy of the results and the calculation time. The tested models had between 597,000 and 2,392,000 finite volumes and varied in partitioning along the axial, radial, and circumferential directions. The calculation step for each discretization variant was selected automatically. The differences in aerodynamic load capacity determined with these models--between the model with the largest and smallest number of finite volumes--reached up to 48%, with a more than fourfold difference in calculation time (7860 s vs. 1740 s). The reduction in the number of finite volumes from 2,392,000 to 1,075,000 no longer had such a large impact on the calculation results in terms of load capacity, as the difference was about 4%, whereas it was assumed that the difference should not exceed 1%. Finally, a model with no more than 2 million finite volumes was selected for further analysis, as both the error and calculation time were at an acceptable level. As the shape of the bearing lubrication gap changed with the position of the journal center, a new calculation mesh was generated for each calculation. Regardless of the journal position in the bearing, the thickness of the lubrication film was divided into 10 segments (Figure 5). To maintain similar geometrical proportions of the generated mesh of the gas domain, parametric relationships were introduced, with the edge length of the finite volume in the circumferential direction dependent on the minimum and maximum thicknesses of the lubrication film (H\({}_{\text{min}}\) and H\({}_{\text{max}}\)). The vapor domain of the working medium was divided into two parts. In the first part, as the radial clearance decreased to H\({}_{\text{min}}\), the mesh in the circumferential direction was made denser. In the second part, as the radial clearance increased to H\({}_{\text{max}}\), the mesh in the circumferential direction became less dense. Such a procedure allowed for the elimination of significant differences in mesh proportions that could adversely affect the accuracy of the obtained results. Each finite volume in the axial direction of the bearing had a length of 1 mm. A symmetry condition was applied to the model, and the average number of finite volumes used in half of the model was 600,000. The boundary conditions of the flow model for the dynamic bearing are shown in Figure 6, where the blue arrows indicate the outlet of the lubricant from the bearing, and the red arrows indicate the plane where the symmetry condition of the bearing is applied. The journal surface was given a counterclockwise rotational speed, which corresponds to the actual operating conditions of the bearing. A constant wall condition was applied to the remaining surfaces. A laminar, isothermal model of gas flow through the bearing was used in the calculations.