Visualization of Flow Direction using Polarization Angle Changes of Cellulose Nanofiber Suspension

In this study, we propose a novel method for visualizing flow direction by exploiting the polarization angle changes of cellulose nanofiber suspensions. Utilizing a polarization camera, we calculate the polarization angle, enabling pixel-wise visualization of flow direction. We demonstrate that the boat's shape significantly influences the flow patterns generated in its wake. Furthermore, we verify the correspondence between polarization angle and flow direction, and investigate the effects of illumination multiplexing and de-multiplexing on the proposed method. This study presents a promising technique for high-resolution flow direction visualization, with potential applications in fluid dynamics research and industrial settings.