Misalignment-Induced Micro-Elastohydrodynamic Lubrication in Rotary Lip Seals

In literature the lubrication of rotary lip seals is explained by hydrodynamic action on a microscopic scale. This theory assumes perfect concentricity between the seal and the shaft which in reality seldomly occurs. Focusing on the stern tube seals application, an analysis is performed on the phenomena distorting the axisymmetric operation of rotary lip seals. Radial and angular shaft misalignments together with pressure and temperature gradients have been modelled. The model predictions are validated using a dedicated setup. Additionally, applying the soft-EHL film thickness expressions at the asperity level, an equivalent film thickness along the circumferential direction is estimated. The Reynolds PDE is solved to predict the misalignment-induced hydrodynamic pressure build-up. The film thickness variation derived and accompanying non-uniform contact pressure distribution was shown to be sufficient for hydrodynamic action and, depending on the minimum film thickness, the hydrodynamic pressure build-up can exceed the static contact pressure. Additionally, significant differences were observed between the radial and angular misalignment configurations.

Non-Newtonian Film Thickness Formation in Ultra-thin Film

This paper aims to show the characteristics of ultra-thin films for non-Newtonian fluid using Ree-Eyring model where intermolecular forces of solvation and Van der Waal's are considered in addition to the hydrodynamic action to fulfill an identified need for such a conjunction. In this case, the film thickness and pressure distribution are obtained by simultaneous solution of the modified Reynolds’ equation incorporating the effect of non-Newtonian fluid, film thickness equation including elastic deformation caused by all contributing pressures and the load balance equation using Newton-Raphson method with Gauss-Seidel iterations. Effect of changing the operating conditions of speed, load, Eyring shear stress and slide-roll ratio on the characteristic of the contact has been studied. The results show that, for the case where the hydrodynamic action is the only pressure acting to support the applied load capacity, the film thickness and the pressure gradient at the exit of the contact obtained using non-Newtonian model is different than that formed using the Newtonian model especially for the increased value of slide-roll ratio. The main results of this study are that for ultra-thin film, the film thickness formed using non-Newtonian model is smaller compared to that obtained using Newtonian case and the discretization of the film thickness as the gap is reduced occurs similar to the results obtained using Newtonian model. The pressure shape shows no difference compared to that formed using the Newtonian case in which an oscillation around the Hertizan contact pressure shape due to the solvation effect appears. The results also show that for ultra-thin film, changing the Eyring shear stress does not affect the film thickness formation.

An Attempt to Quantify the Lag Time of Hydrodynamic Action Based on the Long-Term Monitoring of a Typical Landslide, Three Gorges, China

Hydrodynamic action plays an important role in the development of reservoir bank accumulational landslides. Despite recent concern over hydrodynamic action’s hysteresis effects, there is still no unified efficient method for quantifying lag time, which is a critical input to landslide prediction and early warning systems. To address this shortcoming, we selected a typical landslide, located in Three Gorges Reservoir, China, as a case study. On the basis of long-term monitoring data, we suggest that correlation analysis may work and attempt to use linear correlation first to quantify the lag time. We conclude that, from the macroscopic behavior point of view, linear correlation analysis does not work; neither the daily reservoir water level and its variation nor the daily rainfall and its accumulation exhibit a linear relationship with the surface accumulative displacement. Future studies will use nonlinear correlation analysis to analyze data by different time segments as the hydrodynamic factors have different effects in different periods.