VALIDATION OF TURBULENCE MODELS FOR THE SUPERLAMINAR FLOWS IN JOURNAL BEARINGS

With the development of high speed rotating machinery, the flow regime in bearings changes from laminar to superlaminar, that is, the flow is between laminar and fully developed turbulent. The superlaminar oil flow in an oil lubricated tilting pad journal bearing is analyzed in this study. A three dimensional model for the oil domain is established and the CFD results obtained using laminar and seventeen turbulence models are compared with the experimental results obtained by S.Taniguchi. The seventeen turbulence models are divided into three groups, namely, classical fully developed turbulence models, transition turbulence models, and turbulence models with low Re correction. The laminar and classical turbulence models cannot simulate the superlaminar flow correctly; accordingly, corrections should be applied to classical fully developed turbulence models for superlaminar flows to consider the turbulent effect properly. However, not all corrections are suitable. Among all the compared turbulence models, the SST model with low Re correction performs the best. Furthermore, this model can capture the turbulent effect in superlaminar oil flow, as indicated in the analysis of turbulent viscosity ratio. A comparison of the velocity profiles shows that the mechanism of the superlaminar flow in journal bearings is near wall turbulence. The buffer layer plays an important role in superlaminar flows. The SST model with low Re correction can likewise capture the characteristics of the buffer layer and simulate the near wall turbulence properly in superlaminar flows. Thus in superlaminar journal bearings, the low Re correction is the most suitable correction for the SST turbulence model for simulating oil flows.