Application of transmission photoelasticity in visualizing fluid-structure interactions

Photoelasticity is a stress analysis technique based on the principle that some materials act as waveplates when stressed. In this study, transmission photoelasticity is used as a novel optical technique to capture flow information. A bio-inspired structure is designed comprising a whisker-like shaft inserted into a sensing base made of photoelastic material. When the whisker-inspired structure encounters a flow stimulus, it deflects and generates a high bending stress in the sensing base that is transduced into a fringe pattern that correlates with the flow stimulus. The pattern is observed using a circular polariscope and is then linked to the flow stimulus encountered by the structure. The results show that this optical method can be employed to link a specific fringe pattern with the corresponding free stream velocity with a global accuracy of 85.7%. Also, this technique is able to detect an obstacle upstream of the bio-inspired structure. Transmission photoelasticity could help design flow sensing devices.