The 12th International Conference on Scour and Erosion (ICSE 2025)

The study of fluid-solid interactions has been significantly enhanced by the use of optical visualization techniques, which offer a non-invasive means to observe and analyze the intricate dynamics at play. This method allows for the detailed examination of fluid behavior around solid objects without altering the experimental setup. However, the utility of optical visualization has traditionally been constrained by the requirement for transparent media and the challenges posed by refractive index mismatches between different materials, which can distort visual data. The development of Refractive Index Matching (RIM) technology has been a pivotal breakthrough, enabling researchers to overcome these limitations and achieve precise measurements in complex, multi-material systems. This review article provides an in-depth exploration of the RIM technique, detailing its application across diverse areas of fluid-solid interaction research. It aims to fill a gap in the literature by offering a thorough examination of RIM's role in material selection and its practical applications in engineering contexts. The article also includes a case study that utilizes RIM to explore the complex interactions between vegetation and the flow dynamics associated with dam breaches, highlighting the technique's ability to elucidate real-world phenomena. Furthermore, the review offers strategic recommendations for future research, advocating for the development of RIM materials that are both environmentally friendly and cost-effective, ensuring the technique's ongoing evolution and relevance in the field of fluid-solid interactions.