Experimental Study of Transient Squeezing Film Flow

In this study, we report a novel experimental approach to examine a transient
squeezing flow which is widely observed around the world. However, there is
a lack of investigation captures the feature during the transient flow. An
experimental setup was developed containing a piston instrumented a
displacement sensor and a pressure transducer. The loading surface was
released from rest, creating a fast compaction on the fluid. The motion of the
piston and the corresponding fluid pressure were recorded and compared to
the theory (Lang et al, Physics of Fluids 29.10, 2017: 103606). Excellent
agreements were observed under various conditions, proving the validity of
the theoretical model. The maximum pressure increases with the increase of
the gap height and/or the applied loading. The increase of the fluid viscosity
leads to the decrease of the maximum pressure but extends the time for the
pressure to relax. The extensive experimental and analytical study presented
herein clearly demonstrates 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.