THERMOHYDRODYNAMIC LUBRICATION ANALYSIS INCORPORATING THERMAL-EXPANSION ACROSS THE FILM

The study reported in this paper deals with the development of a therm ohydrodynamic computational procedure for evaluating the pressure, tem perature and velocity distributions in fluid films with fixed geometry between the stationary and moving bearing surfaces. The velocity vari ations and the heat generation are assumed to occur in a central zone with the same length and width as the bearing but with a significantly smaller thickness than the fluid film thickness. The thickness of the heat generation (shear) zone is developed empirically for the best Si t with experimentally determined peak pressures for a journal bearing with a fixed film geometry operating in the laminar regime. A transien t thermohydrodynamic computational model with a transformed rectangula r computational domain is utilized. The analysis can be readily applie d to any given film geometry. The computed distribution of the pressur e in the film is in excellent agreement with the experimental findings for different oils and speeds. The developed procedure gives an analy tical basis for explaining the ''Fogg effect'' where significant press ures can be generated in slider bearings with parallel surfaces as a r esult of the thermal expansion of the film in the direction of the thi ckness. The procedure confirms the experimentally determined square ro ot relationship between the pressure and the sliding velocity reported in references [1-4]. The normalized pressure profiles computed for th e different conditions of the journal bearings are identical to those obtained by isoviscous theory.