Recent Patents on Abnormal Hydrodynamic Thrust Slider Bearings: Part II-the Second Mode of the Bearings

Background: As a successive part, the paper introduces the second mode of abnormal hydrodynamic thrust slider bearings with divergent surface separations registered in the patents, where the boundary slippage is artificially designed both on the stationary surface in the inlet zone and on the whole moving surface. Objective : To introduce a second method for artificially designing the boundary slippage for the formation of abnormal hydrodynamic thrust slider bearings. Methods: The analytical results are presented for the introduced bearings. The performances of the bearings are demonstrated. Result: : In appropriate operating conditions, the introduced bearings can have considerable loadcarrying capacities with low friction coefficients on the scales 10-3 or 10-4. With the weakening of the boundary slippage on the moving surface, the load-carrying capacities of the bearings are all increased, while the friction coefficients of the bearings are all reduced. Conclusion: When the boundary slippage is present both on the stationary surface in the bearing inlet zone and on the whole moving surface, abnormal hydrodynamic thrust slider bearings can be designed with the surface separation in the bearing inlet zone lower than that in the bearing outlet zone. The performances of these bearings are quite satisfactory.

Laboratory Study on the Turbulent Boundary Layers Over Wind-Waves Roughness

A laboratory study of turbulent boundary layers over wind-generated waves using Particle Image Velocimetry (PIV) in a wind-wave flume at the University of Melbourne is presented. The experiments are taken at two different wind speeds of 5.5 and 8.5 m/s at a fetch length of 3.5 m. Two types of multi-camera measurement are specifically tailored to capture the flow behaviours. The first is a measurement with high spatial resolution, with aims of characterizing the mean velocity, surface drag and Reynolds stresses over the non-stationary surface. The second type is a large field-of-view measurement, designed to capture the large-scale turbulent motions which are directly associated with the surface-wave topography. Although the turbulent flow is developed over a non-stationary surface (i.e. wind-generated waves), it embodies similarities in both integral parameters and Reynolds stress behaviours to the turbulent flows over stationary rough surfaces. This observation could open a possibility to develop an important turbulence model as well as drag prediction over wind-generated waves, which could be closely related to stationary rough-wall boundary layers.

Performance of Balancing Wedge Action in Textured Hydrodynamic Pad Bearings

This study investigates a mechanism of textured features taking into account the balance of moment termed “balancing wedge action.” The principle of the suggested mechanism is that a change in moment applied to the lubricated area by incorporating textured features promotes the entire wedge action over the lubricated area. In the current study, multiple dimples are created on the stationary surface of an infinite pad bearing. A one-dimensional incompressible Reynolds equation is solved numerically to determine the load-carrying capacity of infinite pad bearings with a centrally located pivot. Numerical results show the importance of the balancing wedge action. When multiple dimples are created at the inlet side or outlet side of the lubricated area, positive load-carrying capacity is realized. When multiple dimples are located around the central area, no balance solution is obtained for the pad. The dimple depth, width, and distribution are varied to investigate the behavior of the load-carrying capacity realized by the action of the balancing wedge.