Three-dimensional lubrication theory in viscoelastic short-bearing

Abstract

Purpose – The advent of powerful digital computers has seen interest in non-Newtonian fluid mechanics moving towards the solution of complex flow problems for highly elastic liquids in situations of practical importance. Attention must be focussed on the possibility of three-dimensional flow characteristics occurring in seemingly two-dimensional flows. That is the case of the viscoelastic short-bearing. The planar Newtonian case was first studied, but because of the inlet and outlet boundary conditions it was necessary to consider the three-dimensional Newtonian case. There, due to computational difficulties and lack of certitude, it was assumed that the pressure is zero, due to cavitation, over the segment π<<2π. This is an unrealistic assumption. Last investigations proved that, in normal conditions, the cavitation effect is not dominant in journal bearings. The viscoelastic case is even more complicated, and so far it was not possible to tackle the problem in hand in its whole generality. The paper aims to discuss these issues. Design/methodology/approach – Encouraged by the new opportunities above mentioned, the paper ventured to tackle this difficult problem, in the most general conditions, that is without setting any restriction or making limiting assumptions, by the use of three-dimensional numerical methods. As the analytical methods, including the perturbation techniques, are quite inadequate to solve complex flow problems, the paper were compelled to use numerical methods, being meant to choose the treated numerical case typical and of broad application range, thus fitting into overall parameter space of the problem. Findings – The results were satisfactory. Originality/value – The paper determined that the shear-thinning is considerable, and despite the necessary torque remains the same as considered in the previous theoretical analyses, the lifting force is twice its anticipated value, the latter being an important and conclusive proof.