# Fluid Film Bearings and CFD Modeling: A Review

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Fluid Film Bearings

#### 2.1. Theory of Fluid Film Bearings

**Figure 3.**Illustration of an air journal bearing; the pressure holes are distributed equidistantly in the angular coordinates. Geometry of the pressurization orifice–recess (the image is adapted from [5]).

#### 2.2. Journal Bearings

^{−10}kg/m

^{3}). The difference among the forces with inertia and without inertia was calculated in the reference frame R-T for a circular centered orbit (CCO) motion. The values of the differences in forces with respect to the densities are the effects of the inertia/added mass coefficient.

#### 2.3. Grooved Journal Bearings

#### 2.4. Texturized Journal Bearings

#### 2.5. Journal Bearings with Pockets

#### 2.6. Thrust Bearings

#### 2.7. Tilting-Pad Journal Bearings

#### 2.8. Floating Ring Bearings

#### 2.9. Journal Bearing Lubricated with Magnetorheological Fluids

#### 2.10. Aerostatic Bearings

#### 2.11. Journal Bearings with Misalignments

## 3. CFD Transient Analysis of Fluid Film Bearings with the Dynamic Mesh Technique

^{®}, respectively.

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 4.**(

**a**) Skewness mesh generated by modifying the bearing surface with grooves or texture [15]. (

**b**) Dimensions and distribution of herringbone grooves.

**Figure 5.**Boundary conditions of the lubricant film of a journal bearing (plane) for modeling in CFD ANSYS Fluent.

**Figure 6.**Conceptual schematic for a self-circulating bearing. Convergent zone $0<\theta \le \pi $. Divergent zone $\pi <\theta \le 0$ (the image is adapted from [25]).

**Figure 7.**Schematic illustration of a squeeze film damper: (

**a**) damper, (

**b**) FBD; (1) rotor, (2) rolling-element bearing, (3) equivalent journal, (4) squeeze film, (5) housing, (6) anti-rotation pin, (7) whirling ring. O

_{b}, bearing center; O

_{j}, journal center (the image is adapted from [22]).

**Figure 8.**Geometry of the fluid film thickness of a journal bearing with pressurization grooves. The grooves are equidistantly distributed in the angular coordinates.

**Figure 9.**Pressure distribution on grooved bearing pads (modified from [38]). The pressure is concentered on the surface adjacent to the grooves.

**Figure 10.**Longitudinal section of a journal bearing: (

**a**) conventional bearing; (

**b**) bearing with a circumferential feeding groove [6].

**Figure 11.**Schematic of a textured bearing and groove (the image is adapted from [44]).

**Figure 12.**Coordinate system and groove patterns: (

**a**) when the slave (bearing surface) is grooved (PJGS); (

**b**) when the journal is grooved (GJPS) (modified of [48]).

**Figure 13.**Fluid film model of a hydrodynamic bearing. The pressurization in the recesses and pockets makes it a hybrid bearing (modified from [53]).

**Figure 14.**A capillary-compensated four-pocket hydrostatic journal bearing system and coordinate system (modified of [56]). Each pocket is equidistantly distributed, and the area is the same for all pocket shapes.

**Figure 15.**(

**a**) Schematic diagram of an oil pad structure with the pressure distribution. (

**b**) Diagram of the static equilibrium of an oil pad (modified from [57]).

**Figure 16.**Schematic of a tilting-pad journal bearing (modified from [62]). The position of the pads changes when a disturbing force is applied to the journal.

**Figure 17.**Schematic of a floating ring bearing. The ring rotates at a speed different from that of the journal.

**Figure 18.**General geometry and characteristics of a journal bearing lubricated with MR fluids. The power source $H$ provides a current that modifies the viscosity and yield stress with a magnetic field (the image is adapted from [74]).

**Figure 19.**(

**a**) Various types of orifice chamber shapes. (

**b**) Streamlines and turbulent kinetic energy contours for various chamber shapes modified (the image is adapted from [83]).

**Figure 20.**Geometry and motion of a journal bearing with misalignments. (

**a**) Position of the journal when there are misalignments in the x and y directions: misalignments in the (

**b**) x direction and (

**c**) y direction (the image is adapted from [18]).

**Figure 21.**(

**a**) Geometry of the rotor–bearing system; (

**b**) comparison of loci among different rotor–bearing models (rigid model; Babbitt and steel bearing vs. steel rotor model; nylon and steel bearing vs. steel rotor; nylon bearing vs. steel rotor) (the image is adapted from [98]).

**Figure 22.**Structured grid: (

**a**) initial grid; (

**b**) final grid after applying the update of the nodal positions (the image is adapted from [99]). The quality of the structured mesh is maintained.

**Figure 23.**Differences in the oil film force with linear-displacement perturbation (the image is adapted from [104]). The initial shock is temporary and occurs at the beginning of the linear movement.

**Table 1.**Comparison of simulations of bearings with four axial grooves and bearings without groove [40].

$\mathit{e}$ | $\mathit{\varphi}$ (deg) | $\mathsf{\Delta}{\mathit{T}}_{\mathit{m}\mathit{a}\mathit{x}}$ [K] | $\mathsf{\Delta}{\mathit{T}}_{\mathit{a}\mathit{v}\mathit{e}}$ [K] | Mass$\mathbf{Flow}\text{}\mathbf{[}\mathbf{k}\mathbf{g}/{\mathbf{m}}^{3}\mathbf{]}$ | Viscous Torque [N m] | |
---|---|---|---|---|---|---|

Without grooves | 0.1936 | 83.4832 | 1.3 | 2.185 | 2.82611 × 10^{−5} | 3.3935 × 10^{−4} |

With grooves | 0.2381 | 63.1236 | 1.7 | 0.665 | 10.7848 × 10^{−5} | 3.2221 × 10^{−4} |

Values of difference | 22% | −24% | −82% | −228% | 282% | −5% |

Type of Fluid Film Bearing | Characteristics | Applications |
---|---|---|

Journal bearings (plain) | Their load capacity and operation speeds are high for heavy loads (LDN) [1,2], and the wear and stability are low, but the modeling is simple [22,27]. | Fluid films are used to support rotors whose direction of load is normal to the axis of the shaft; for example, ships, generators, turbines, compressors, and others in the automotive, naval, aviation, power generation, construction, and mining industries. Generally, thrust bearings are used in conjunction with journal bearings in many machine tools. However, they are often used in machinery where high accuracy and stability are needed. Aerostatic bearings are also used in many applications where high precision of positioning is required. |

Grooved journal bearing | Their load capacity and operation speeds are high for light loads (LDN); the wear is very low and allows pressurization. the grooves are symmetrically distributed, and the number and geometry are limited [15,18]. Modeling is not difficult [38,39]. | |

Texturized journal bearings | They are suitable for light loads (LDN) at high operating speeds with high stability. The wear is very low and the texture reduces the size of bubbles generated through cavitation [45]. The texture must be in the convergent zone [45,46,47] with limited dimensions. Modeling is not difficult. | |

Journal bearings with pockets | The size of bubbles generated through cavitation is reduced; they allow hybrid operation (lubricant is pressurized) [54,55,56]. Their load capacity (LDN) is high for light loads, the pockets are symmetrically distributed [53], and the modeling is not difficult. | |

Thrust bearings | The load capacity (LDP) is high with low friction and wear. External pressurization increases their stiffness [57], but they operate at low speeds. The modeling is simple, and it is possible to model a section of the entire model [38,39]. | |

Tilting pad journal bearing | They are suitable for heavy loads (LDN) at high operating speeds with high stability [1,2]. The wear is very low, but a reliable oil supply system is necessary; therefore, they can be preloaded. Modeling is very difficult [63,64,68,69]. | |

Floating ring bearing | They have a simple structure and the characteristic of double oil–film support with high efficiency and stability [106]. The inner layer of the fluid becomes hotter. The modeling is difficult. | |

Journal bearing lubricated with an MRF | The fluid properties can be controlled [74]; therefore, the static and dynamic characteristics are variable. However, the fluid temperature is high due to the friction and relatively small load capacity (LDN). The magnetic field produces particle adhesion [77,78,79]. The modeling is difficult. | |

Aerostatic bearing | External pressurization is necessary for their functionality at high speeds; they have low driving power and friction, thermal stability, and low load capacity (LDN) [3]. The clearance, hole diameter, and pressure are factors that affect the static parameters [5,81]. The pressure generates vortices; therefore, the orifice chamber shapes are necessary to suppress the vortices [81,83,84]. | |

Journal bearings with misalignment | These bearings consider misalignment in the analysis and modeling. The analysis is similar to that of the bearings above [85,90]. The analysis is harder [31,33]. The static parameters are widely affected by misalignment [91,92]. |

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© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Pérez-Vigueras, D.; Colín-Ocampo, J.; Blanco-Ortega, A.; Campos-Amezcua, R.; Mazón-Valadez, C.; Rodríguez-Reyes, V.I.; Landa-Damas, S.J.
Fluid Film Bearings and CFD Modeling: A Review. *Machines* **2023**, *11*, 1030.
https://doi.org/10.3390/machines11111030

**AMA Style**

Pérez-Vigueras D, Colín-Ocampo J, Blanco-Ortega A, Campos-Amezcua R, Mazón-Valadez C, Rodríguez-Reyes VI, Landa-Damas SJ.
Fluid Film Bearings and CFD Modeling: A Review. *Machines*. 2023; 11(11):1030.
https://doi.org/10.3390/machines11111030

**Chicago/Turabian Style**

Pérez-Vigueras, Demetrio, Jorge Colín-Ocampo, Andrés Blanco-Ortega, Rafael Campos-Amezcua, Cuauhtémoc Mazón-Valadez, Víctor I. Rodríguez-Reyes, and Saulo Jesús Landa-Damas.
2023. "Fluid Film Bearings and CFD Modeling: A Review" *Machines* 11, no. 11: 1030.
https://doi.org/10.3390/machines11111030