Two-scale EHL: Three-dimensional topography in tilted-pad bearings

G.N De Boer,R.W Hewson,H.M Thompson,L Gao,V.V Toropov

doi:10.1016/j.triboint.2014.05.019

Abstract

Derived from the Heterogeneous Multiscale Methods (HMM), a two-scale method is developed for the analysis of Elastohydrodynamic Lubrication (EHL) and micro-EHL in tilted-pad bearings with three-dimensional topography. A relationship linking the pressure gradient to mass flow rate is derived and represented in the bearing domain through homogenisation of near-periodic simulations describing the Fluid Structure Interaction (FSI) of topographical features. For the parameters investigated the influence of compressibility and piezoviscosity was found to be more significant than that of non-Newtonian (shear-thinning) behaviour on textured bearing performance. As the size of topography increased two-scale solutions demonstrated that at constant load the coefficient of friction increased and the minimum film thickness decreased over a range of pad lengths and tilt angles.

Highlights

The Reynolds equation [1] is well established as an accurate means of describing fluid flow in the Elastohydrodynamic Lubrication (EHL) of smooth surface geometries [2]
The inclusion of inertial effects via the generalised Reynolds equation [17] or Navier–Stokes equations illustrated the influence of inertia on load capacity and the consequent benefit of using Computational Fluid Dynamics (CFD) to model the fluid film flow
The first describes the numerical accuracy of the two scale method, the second subsection analyses the small scale simulations, and the third analyses contains results relating to smooth and textured surfaces at the large scale

Summary

Introduction

The Reynolds equation [1] is well established as an accurate means of describing fluid flow in the Elastohydrodynamic Lubrication (EHL) of smooth surface geometries [2]. As topographical features become more important flow analyses based on solutions of the Stokes or Navier–Stokes equations have been shown to be more accurate than those based on the traditional Reynolds equation [9]. Studies which compare solutions to Reynolds, Stokes and Navier–Stokes equations for textured surfaces have been conducted by a number of researchers [10,11,12,13,14,15]. The inclusion of inertial effects via the generalised Reynolds equation [17] or Navier–Stokes equations illustrated the influence of inertia on load capacity and the consequent benefit of using Computational Fluid Dynamics (CFD) to model the fluid film flow. CFD has been used on smooth geometries to enable the modelling of a range of phenomena which occur in EHL such as thermal transport, rheology, cavitation [18], wall slip [19] and structural models [20]

Objectives

Methods

Results

Conclusion