Behavior analysis of air bubbles in the oil lubricant of FDBs at low speed operating conditions

Abstract

This paper investigated the behavior of the air bubbles and the air–oil interface of FDBs at low speed operating conditions by using a two-phase flow analysis of air and oil to study the expelling mechanism of air bubbles in the operation of FDBs. The two-phase flow of air and oil was analyzed using the three-dimensional Navier–Stokes equation and the volume of fluid method of multi-phase flow. The proposed numerical method was verified by the experimental results. The effects of the depth and area of the groove near the outlet on the behavior of the air bubbles and the air–oil interface were also studied. This research shows that the groove near the outlet is responsible for the concave shape of the air–oil interface as a result of surface tension, and that air bubbles are expelled into the outside air when an air bubble meets the concave air–oil interface.