Para‑cymene solutions for index‑matching to acrylic
To deploy optical diagnostics such as particle image velocimetry or planar laser-induced fluorescence (PLIF) in complex geometries, it is beneficial to use index-matched facilities. A binary mixture of para-cymene and cinnamaldehyde provides a viable option for matching the refractive index of acrylic, a common material for scaled models and test sections. This fluid is particularly appropriate for large-scale facilities and when a low-density and low-viscosity fluid is sought, such as in fluid–structure interaction studies. This binary solution has relatively low kinematic viscosity and density; its use enables the experimentalist to select operating temperature and to increase fluorescence signal in PLIF experiments.
Main publications
L LONGO, R CAPANNA, G RICCIARDI, and PM BARDET. Threshold of Keulegan–Carpenter instability within a 6 × 6 rod bundle. Experimental Thermal and Fluid Science. 157:111231, https://doi.org/10.1016/j.expthermflusci.2024.111231 (2024).
R CAPANNA, E SARROUY, G RICCIARDI, and PM BARDET. Modal contribution of bundle oscillation to induced flow. Journal of Fluids and Structures. 111:103557, https://doi.org/10.1016/j.jfluidstructs.2022.103557 (2022).
C FORT, CD FU, N WEICHSELBAUM, and PM BARDET. Refractive index and solubility control of para‑cymene solutions for index‑matched fluid–structure interaction studies, Experiments in Fluids. 56:210, https://doi.org/10.1007/s00348-015-2080-x (2015).
Polymer index-matched with water
In experimental fluid dynamics, it would be invaluable to have solids with a refractive index similar to that of water, hence simplifying the use of existing facilities to study flows around complex geometries. We reported a polymer that is refractive-index-matched with water at room temperature and can be cast in thick specimens. We successfully demonstrated its use with three common laser-based diagnostics: laser-induced fluorescence, particle image velocimetry, and molecular tagging velocimetry.
Main publication
C FORT and PM BARDET. Refractive-index-matched polymer for experimental fluid dynamics in water. Experiments in Fluids. 62:249, https://doi.org/10.1007/s00348-021-03347-9 (2021).