Two-dimensional flow of a non-Newtonian lubricant

The traction coefficients predicted in an elastohydrodynamic contact with a Newtonian fluid are impossibly large, so that methods of analysing the beh aviour of a non-Newtonian fluid are essential. Except for one-dimensional f low, no convenient exact method is known. Two approximate methods of treati ng the flow of a non-Newtonian lubricant, proposed by Ehret et al. and Hook e respectively, are examined by comparing their predictions for a particula r non-Newtonian fluid for which an exact solution may readily be obtained. While there is no reason to believe that any real fluid exhibits this behav iour, it is not too different from Eyring behaviour, so that the conclusion s are believed to be applicable to real fluids. A method of obtaining an exact solution for a general non-Newtonian lubrica nt is investigated, although it appears to involve too much computation for use in an elastohydrodynamic lubrication (EHL) solver. A limited number of full solutions obtained for an Eyring fluid support the conclusions deduce d using the model fluid, namely that the approximations will be quite adequ ate for the analysis of EHL of smooth surfaces and may be good enough for w avy or rough surfaces.