Multiphase Computational Fluid Dynamics Modeling of External Oil Flow From a Journal Bearing

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Richard Jefferson-Loveday ◽  
Colin Young ◽  
Benjamin C. Rothwell ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Phase Interface ◽  
Ansys Fluent ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Oil Flow

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly, in a planetary configuration, the kinematic conditions are complex. With the planet gears rotating about their own axes and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. Computational fluid dynamics (CFD) simulations using the volume of fluid (VoF) method are carried out in ANSYS fluent (ANSYS, 2013, “ANSYS Fluent User's Guide,” ANSYS Inc., Canonsburg, PA) to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing. This paper presents an investigation of two numerical schemes that are available in ansysfluent to track or capture the air–oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e., concentric, lubricating gap. Based on these simplifications, a three-dimensional (3D) CFD sector model with rotationally periodic boundaries is considered. A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regard to the accuracy of the phase interface reconstruction and the time required to reach steady-state flow-field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path, and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used. With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.

scholarly journals Multiphase CFD Modeling of External Oil Flow From a Journal Bearing

2018 ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Richard Jefferson-Loveday ◽  
Benjamin C. Rothwell ◽  
Colin Young
Keyword(s):  
Boundary Conditions ◽  
Journal Bearing ◽  
Flow Behavior ◽  
Phase Interface ◽  
Numerical Schemes ◽  
Ansys Fluent ◽  
Oil Film ◽  
Reconstruction Scheme ◽  
Geometric Reconstruction ◽  
Oil Flow

High loads and bearing life requirements make journal bearings a potential choice for use in high power, epicyclic gearboxes in jet engines. Particularly in a planetary configuration the kinematic conditions are complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. Computational Fluid Dynamics (CFD) simulations using the Volume of Fluid (VoF) method are carried out in ANSYS Fluent [1] to numerically model the two-phase flow behavior of the oil exiting the bearing and merging into the air surrounding the bearing. This paper presents an investigation of two numerical schemes that are available in ANSYS Fluent to track or capture the air-oil phase interface: the geometric reconstruction scheme and the compressive scheme. Both numerical schemes are used to model the oil outflow behavior in the most simplistic approximation of a journal bearing: a representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. Based on these simplifications, a three dimensional (3D) CFD sector model with rotationally periodic boundaries is considered. A comparison of the geometric reconstruction scheme and the compressive scheme is presented with regards to the accuracy of the phase interface reconstruction and the time required to reach steady state flow field conditions. The CFD predictions are validated against existing literature data with respect to the flow regime, the direction of the predicted oil flow path and the oil film thickness. Based on the findings and considerations of industrial requirements, a recommendation is made for the most suitable scheme to be used. With a robust and partially validated CFD model in place, the model fidelity can be enhanced to include journal bearing eccentricity. Due to the convergent-divergent gap and the resultant pressure field within the lubricating oil film, the outflow behavior can be expected to be very different compared to that of a concentric journal bearing. Naturally, the inlet boundary conditions for the oil emerging from the journal bearing into the external environment must be consistent with the outlet conditions from the bearing. The second part of this paper therefore focuses on providing a method to generate appropriate inlet boundary conditions for external oil flow from an eccentric journal bearing.

scholarly journals Towards Investigation of External Oil Flow From a Journal Bearing in an Epicyclic Gearbox

2017 ◽  
Author(s):  
Martin Berthold ◽  
Hervé Morvan ◽  
Colin Young ◽  
Richard Jefferson-Loveday
Keyword(s):  
Flow Field ◽  
Journal Bearing ◽  
Numerical Models ◽  
Flow Behavior ◽  
Phase Interface ◽  
Journal Bearings ◽  
Field Behavior ◽  
Oil Flow ◽  
Inlet Conditions ◽  
Near Wall

High loads and bearing life requirements make journal bearings the preferred choice for use in high power, epicyclic gearboxes in jet engines. In contrast to conventional, non-orbiting journal bearings in epicyclic star gearboxes, the kinematic conditions in epicyclic planetary arrangements are much more complex. With the planet gears rotating about their own axis and orbiting around the sun gear, centrifugal forces generated by both motions interact with each other and affect the external flow behavior of the oil exiting the journal bearing. This paper presents a literature and state-of-the-art knowledge review to identify existing work performed on cases similar to external journal bearing oil flow. In order to numerically investigate external journal bearing oil flow, an approach to decompose an actual journal bearing into simplified models is proposed. Later, these can be extended in a step-wise manner to allow key underlying physical phenomena to be identified. Preliminary modeling considerations will also be presented. This includes assessing different geometrical inlet conditions with the aim of minimizing computational requirements and different numerical models for near-wall treatment. The correct choice of near-wall treatment models is particularly crucial as it determines the bearing’s internal and external thermal behavior and properties. The findings and conclusions are used to create a three dimensional (3D), two-component computational fluid dynamic (CFD) sector model with rotationally periodic boundaries of the most simplistic approximation of an actual journal bearing: a non-orbiting representation, rotating about its own axis, with a circumferentially constant, i.e. concentric, lubricating gap. The inlet boundary conditions for simulating the external oil flow are generated by partly simulating the internal oil flow within the lubricating gap. In order to track the phase interface between the oil and the air surrounding the bearing, the Volume of Fluid (VoF) method is used. The quality of the CFD simulations of the domain of interest is not only dependent on the accuracy of the inlet conditions, but is also dependent on the computational mesh type, cell count, cell shape and numerical methods used. External journal bearing oil flow was simulated with a number of different mesh densities and the effect on the flow field behavior will be discussed. Two different operating temperatures, representing low and high viscosity oil, were used and their effect on the flow field behavior will also be assessed. In order to achieve the future objective of creating a design tool for routine use, key areas will be identified in which further progress is required. This includes the need to progressively increase the model fidelity to eventually simulate an orbiting journal bearing in planetary configuration with an eccentric, i.e. convergent-divergent, lubricating gap.

Three-Dimensional Thermo-Elasto-Hydrodynamic Computational Fluid Dynamics Model of a Tilting Pad Journal Bearing—Part I: Static Response

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jongin Yang ◽  
Alan Palazzolo
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Boundary Conditions ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Cfd Model ◽  
Flow And Heat Transfer ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing

This paper presents the first simulation model of a tilting pad journal bearing (TPJB) using three-dimensional (3D) computational fluid dynamics (CFD), including multiphase flow, thermal-fluid, transitional turbulence, and thermal deformation of the shaft and pads employing two-way fluid–structure interaction (FSI). Part I presents a modeling method for the static performance. The model includes flow between pads BP, which eliminates the use of an uncertain, mixing coefficient (MC) in Reynold's equation approaches. The CFD model is benchmarked with Reynold's model with a 3D thermal-film, when the CFD model boundary conditions are consistent with the Reynolds boundary conditions. The Reynolds model employs an oversimplified MC representation of the three-dimensional mixing effect of the BP flow and heat transfer, and it also employs simplifying assumptions for the flow and heat transfer within the thin film between the journal and bearing. This manufactured comparison shows good agreement between the CFD and Reynold's equation models. The CFD model is generalized by removing these fictitious boundary conditions on pad inlets and outlets and instead models the flow and temperature between pads. The results show that Reynold's model MC approach can lead to significant differences with the CFD model including detailed flow and thermal modeling between pads. Thus, the CFD approach provides increased reliability of predictions. The paper provides an instructive methodology including detailed steps for properly applying CFD to tilt pad bearing modeling. Parts I and II focus on predicting static and dynamic response characteristic responses, respectively.

scholarly journals A Simple Transient Poiseuille-Based Approach to Mimic the Womersley Function and to Model Pulsatile Blood Flow

Dynamics ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 9-17
Author(s):  
Andrea Natale Impiombato ◽  
Giorgio La Civita ◽  
Francesco Orlandi ◽  
Flavia Schwarz Franceschini Zinani ◽  
Luiz Alberto Oliveira Rocha ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Boundary Conditions ◽  
Quadratic Function ◽  
Pulsatile Blood Flow ◽  
Flow Through ◽  
Simplified Analysis ◽  
Function Models ◽  
Flow Reversals

As it is known, the Womersley function models velocity as a function of radius and time. It has been widely used to simulate the pulsatile blood flow through circular ducts. In this context, the present study is focused on the introduction of a simple function as an approximation of the Womersley function in order to evaluate its accuracy. This approximation consists of a simple quadratic function, suitable to be implemented in most commercial and non-commercial computational fluid dynamics codes, without the aid of external mathematical libraries. The Womersley function and the new function have been implemented here as boundary conditions in OpenFOAM ESI software (v.1906). The discrepancy between the obtained results proved to be within 0.7%, which fully validates the calculation approach implemented here. This approach is valid when a simplified analysis of the system is pointed out, in which flow reversals are not contemplated.

scholarly journals Journal Bearing: An Integrated CFD-Analytical Approach for the Estimation of the Trajectory and Equilibrium Position

2020 ◽  
Vol 10 (23) ◽  
pp. 8573
Author(s):  
Franco Concli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pressure Distribution ◽  
Equilibrium Position ◽  
Analytical Approach ◽  
Journal Bearing ◽  
Cfd Model ◽  
Cavitation Model ◽  
Computational Fluid Dynamics Cfd ◽  
The Mathematical Model

For decades, journal bearings have been designed based on the half-Sommerfeld equations. The semi-analytical solution of the conservation equations for mass and momentum leads to the pressure distribution along the journal. However, this approach admits negative values for the pressure, phenomenon without experimental evidence. To overcome this, negative values of the pressure are artificially substituted with the vaporization pressure. This hypothesis leads to reasonable results, even if for a deeper understanding of the physics behind the lubrication and the supporting effects, cavitation should be considered and included in the mathematical model. In a previous paper, the author has already shown the capability of computational fluid dynamics to accurately reproduce the experimental evidences including the Kunz cavitation model in the calculations. The computational fluid dynamics (CFD) results were compared in terms of pressure distribution with experimental data coming from different configurations. The CFD model was coupled with an analytical approach in order to calculate the equilibrium position and the trajectory of the journal. Specifically, the approach was used to study a bearing that was designed to operate within tight tolerances and speeds up to almost 30,000 rpm for operation in a gearbox.

Transportation Performance of Highly Concentrated Coal-Water Slurries Prepared from Indian Coals

2014 ◽  
Vol 592-594 ◽  
pp. 869-873 ◽  
Author(s):  
Arunanshu Chakravarthy ◽  
Satish Kumar ◽  
S.K. Mohapatra
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Rheological Behaviour ◽  
Pseudoplastic Fluid ◽  
Ansys Fluent ◽  
Water Slurry ◽  
Solids Concentration ◽  
Coal Water Slurry ◽  
Indian Coals ◽  
Fluid Behaviour

The rheological behaviour of concentrated coal-water slurries prepared from three different Indian coals were investigated using an Anton Paar rheometer. The perspective was laid in to study the effect of solids concentration on the rheological behaviour of coal water slurry. It was observed that coal water slurry exhibited non-Newtonian pseudoplastic fluid behaviour at concentrations above 30 % by weight. The apparent viscosity varied with the amount of coal in the slurry. The rheological data were utilized to predict the pressure drop characteristics of coal water slurry flowing through a 53 mm diameter slurry pipeline using ANSYS Fluent 14.0 computational fluid dynamics code.

Fish-friendly design of an axial flow pump impeller based on a blade strike model

2019 ◽  
Vol 234 (2) ◽  
pp. 173-186 ◽  
Author(s):  
Qiang Pan ◽  
Weidong Shi ◽  
Desheng Zhang ◽  
BPM van Esch ◽  
Ruijie Zhao
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Behavior ◽  
Integrated Design ◽  
Axial Flow ◽  
Hydraulic Performance ◽  
Fish Mortality ◽  
Computational Fluid Dynamics Analysis ◽  
Axial Flow Pump ◽  
Flow Pump

With environmental awareness growing in many countries, governments are taking measures to reduce mortality of migrating fish in pumping stations. Manufacturers seek to develop pumps that are less damaging to fish and still provide good hydraulic performance, but little is known about the implications design modifications may have on internal flow characteristics and overall hydraulic performance. In this paper, an integrated design method is proposed that combines a validated blade strike model for fish damage and a computational fluid dynamics method to assess the pump performance. A redesign of an existing, conventional, axial flow pump is presented as an example in this paper. It shows how the design of the impeller blades was modified stepwise in order to reduce fish mortality while its hydraulic performance was monitored. Computational fluid dynamics analysis of the flow near the hub of the highly skewed blades indicated that unconventional design modifications were required to ensure optimum flow behavior. In the final fish-friendly design, the risk of fish mortality has reduced considerably while the hydraulic performance of the pump is still acceptable for practical application.

Experimental and simulation study of thermal accumulation in an enclosed vehicle

2019 ◽  
Vol 233 (14) ◽  
pp. 3621-3629
Author(s):  
Sing Ngie David Chua ◽  
Boon Kean Chan ◽  
Soh Fong Lim
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
Heat Accumulation ◽  
Ansys Fluent ◽  
Direct Exposure ◽  
Car Park

Thermal accumulation in a car cabin under direct exposure to sunlight can be extremely critical due to the risk of heatstroke especially to children who are left unattended in the car. There are very limited studies in the literature to understand the thermal behaviour of a car that is parked in an open car park space and the findings are mostly inconsistent among researchers. In this paper, the studies of thermal accumulation in an enclosed vehicle by experimental and computational fluid dynamics simulation approaches were carried out. An effective and economical method to reduce the heat accumulation was proposed. Different test conditions such as fully enclosed, fully enclosed with sunshade on front windshield and different combinations of window gap sizes were experimented and presented. Eight points of measurement were recorded at different locations in the car cabin and the results were used as the boundary conditions for the three-dimensional computational fluid dynamics simulation. The computational fluid dynamics software used was ANSYS FLUENT 16.0. The results showed that the application of sunshade helped to reduce thermal accumulation at car cabin by 11.5%. The optimum combination of windows gap size was found to be with 4-cm gap on all four windows which contributed to a 21.1% reduction in car cabin temperature. The results obtained from the simulations were comparable and in agreement with the experimental tests.

Three-Dimensional Thermo-Elasto-Hydrodynamic Computational Fluid Dynamics Model of a Tilting Pad Journal Bearing—Part II: Dynamic Response

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Jongin Yang ◽  
Alan Palazzolo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Dynamic Response ◽  
Journal Bearing ◽  
Three Dimensional ◽  
Static Response ◽  
Damping Coefficients ◽  
Tilting Pad ◽  
Stiffness And Damping ◽  
Tilting Pad Journal Bearing

Part II presents a novel approach for predicting dynamic coefficients for a tilting pad journal bearing (TPJB) using computational fluid dynamics (CFD) and finite element method (FEM), including fully coupled elastic deflection, heat transfer, and fluid dynamics. Part I presented a similarly novel, high fidelity approach for TPJB static response prediction which is a prerequisite for the dynamic characteristic determination. The static response establishes the equilibrium operating point values for eccentricity, attitude angle, deflections, temperatures, pressures, etc. The stiffness and damping coefficients are obtained by perturbing the pad and journal motions about this operating point to determine changes in forces and moments. The stiffness and damping coefficients are presented in “synchronously reduced form” as required by American Petroleum Institute (API) vibration standards. Similar to Part I, an advanced three-dimensional thermal—Reynolds equation code validates the CFD code for the special case when flow Between Pad (BP) regions is ignored, and the CFD and Reynolds pad boundary conditions are made identical. The results show excellent agreement for this validation case. Similar to the static response case, the dynamic characteristics from the Reynolds model show large discrepancies compared with the CFD results, depending on the Reynolds mixing coefficient (MC). The discrepancies are a concern given the key role that stiffness and damping coefficients serve instability and response predictions in rotordynamics software. The uncertainty of the MC and its significant influence on static and dynamic response predictions emphasizes a need to utilize the CFD approach for TPJB simulation in critical machines.

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