Experimental study of transient squeezing film flow

In this paper, we report an experimental approach to examine a fast-developing flow in a thin fluid gap. The phenomenon is widely observed in industrial applications, e.g., squeeze dampers, and in biological systems, e.g., joints lubrication. However, experimental investigations that capture the transient nature of the flow during the process are lacking. An experimental setup, consisting of a piston equipped with a laser displacement sensor and a pressure transducer, was developed. The loading surface was released from rest, creating a fast compaction on the fluid. The motion of the piston and the resulting changes of fluid pressure were recorded and compared to four representative theoretical models. The results show that the maximum pressure increases with gap height and/or the applied loading. A higher fluid viscosity leads to a lower maximum pressure but significantly extends the fluid pressure relaxation time. It is clearly demonstrated that the pressure response is governed by both the inertial effect due to the local acceleration, and the viscous effect due to the stokes resistance, revealing fundamental physics during the fast-developing squeezing flow process.