Stress field visualization of Saffman-Taylor instability in Hele-Shaw cell*

When a less viscous fluid displaces a more viscous one in small space, such as porous media or Hele-Shaw cells, the interface forms a finger-like pattern due to hydrodynamic instability caused by the viscosity difference. This is known as Saffman-Taylor instability or viscous fingering (VF). Understanding of VF is important because it is related to the various applications such as enhanced oil recovery and chromatography. The previous theoretical, experimental, and numerical approaches pointed out that the three-dimensional structure inside the gap of Hele-Shaw cell plays an important role in the onset and suppression of VF. In this study, the photoelastic measurement of VF in a Hele-Shaw cell was performed to visualize stress field including three-dimensional effects. The interpretation of the experimental results were discussed by comparing of results in radial Hele-Shaw flow with numerical results. We will provide the effective explanation of the flow during fluid displacements in the Hele-Shaw cell by using the measurement results of the stress field.