Clarifications of the mechanism of nano-fluctuation of aerostatic thrust bearing with surface restriction

Fluctuations of objects supported by aerostatic bearings are a severe problem for ultraprecise positioning technology. The cause of small fluctuations, called nano-fluctuations of objects supported by the thrust bearing was investigated. An aerostatic thrust bearing with surface restriction by T-shaped grooves was the focus of this study. A computational fluid analysis of the airflow around the bearing was conducted and compared with experimental photographs. In addition, the amount of nano-fluctuations was measured by changing the bearing clearance and inlet pressure of the bearing. The nano-fluctuation was induced by the fluctuation of atmospheric pressure due to the unsteady airflow around the bearing edge, and the amount of the fluctuation depended on the Reynolds number corresponding to the flow velocity.