Razavi S. Hydrodynamic features of the flow of abnormally viscous liquids in a conical sliding surface

The dissertation is devoted to the studying of the hydrodynamics influence of viscous and anomalously viscous lubricants in conical gaps with a variable taper value. Such tasks are relevant in the studying of tapered support bearings, which are widely used in hydraulic turbine engineering and other areas of hydraulic engineering. One of the important issues in this direction is the determination of the torque of viscous friction forces in the conical slotted gaps. In the work, а critical analysis of studies was carried out, a conclusion was drawn on the insufficiency of research and a task was set, the solution of which is proposed in this paper. Basing on the studies of other authors, the main similarity criteria have been derived, which is able to characterize this process of fluid behavior in the gap, where one of the surfaces (internal) is able to rotate around its axis. The physical and mathematical modeling of the behavior of fluids in tapered bearings is conducted. Basing on experimental studies, functional dependencies of torque determination as a function of the rotational speed of the internal cone, the viscosity of the lubricant, the width of the gap between the conical surfaces were obtained. The obtained results were compared with similar data for cylindrical slotted gaps (cylindrical sliding bearings). The recommendations for the calculation of the main characteristics of the stream are presented. The performed mathematical modeling made it possible to estimate the degree of difference between the results of the experiment and the theory, to explain the discrepancies in the results. One of the most important points of the study is the result associated with the behavior of abnormally viscous liquids (some of the lubricants are similar in their behavior to liquids, whose behavior is able to be described by the Oswald de Ville equation). The simulation of the considered processes in the tapered slotted gaps made it possible to ensure a rational choice of lubricants to reduce the friction torque (friction forces) in the conical gaps.