The slippage effect at the interface between a confined fluid and the surface around it has a potential application in microfluidic and nanofluidic devices. To investigate the slippage effect of fluid on superhydrophobic surfaces, a series of rheological experiments are carried out for superhydrophobic surfaces coated with carbon nanotube forests (CNTs), which are prepared by the chemical vapor deposition method (CVD). The results show that such surfaces can create certain slippage effects for a fluid flowing over them and that the slip length is in accordance with the theoretical prediction as well as the value measured through other experimental methods. As the same trend is observed for both the theoretical and experimental slip lengths, the theoretical model can be used to optimize the superhydrophobic surfaces for the slippage effect or drag reduction. The superhydrophobic surfaces with considerable slippage effects have broad potential application in micro- and nanofluidic devices or biodevices to solve the fluid resistance problem.

To improve the tribological performance of mating surfaces such as journal bearings, dimples with different shapes were introduced through laser surface texturing. In laser surface texturing processes, bulges are always induced around the dimples and may influence the tribological performance of the surface. In this article, the influence of the bulges on the tribological performance of a journal bearing is numerically investigated. Variations in both the friction coefficient and the eccentricity ratio of a journal bearing with the width and height of the bulges are studied. The influence of the radius of the dimples on the tribological performance of a journal bearing is also investigated. Results show that the friction coefficient increases with both the width and the height of bulges in the case of journal bearing under light and moderate loading conditions, which is in accord with the experimental results in previous works. The linear variation in the friction coefficient with the height of the bulges indicates that the wear rate of the bulges may be investigated by monitoring the friction coefficient. The abnormality of friction coefficient variation with the width of the bulges in the case of heavy loading condition indicates that introducing the bulges is an effective approach for reasonable tribological performance. From the results for the influence of the dimple radius, it can be concluded that although the introduction of dimples can improve the tribological performance, it also has some disadvantages such as decreasing the load-carrying capacity.

A procedure based on Kåsa fit for evaluating the surface roughness of a curved surface with a circular arc profile was suggested in this paper. To investigate the effectiveness of the method, some curved surface profiles with preset surface roughness were numerically generated, and their surface roughness was evaluated by the procedure based on Kåsa fit. And the surface roughness of two experimental surface profiles evaluated by the method based on Kåsa fit was compared with those evaluated by linear fitting and quadratic polynomial fitting to demonstrate both the effectiveness and the preservation of Kåsa fit-based procedure. Results show that the evaluated value of surface roughness by Kåsa fit-based procedure only deviated from the actual value by less than 10%, even in the case of considerable fitting parameters’ error (>30%). Also, the Kåsa fit can report a reasonable value of surface roughness with better preservation of shift and rotation motion of the surface profile compared to both linear fit and quadratic polynomial fitting, especially for the curved surface with a short radius. This procedure based on Kåsa fit can be used in evaluating surface roughness of curved surface with circular arc profile no matter what pose of the object under observed.