Designing and optimizing multi-tracer PLIF for application in variable-density turbulent mixing environment

Measuring the volume fraction of multiple components simultaneously is a challenge for mixing studies across a variety of different fields. In multilayer studies on the Rayleigh-Taylor and Richtmyer-Meshkov instabilities, experiments have been limited by single-tracer planar laser induced fluorescence (PLIF) to volume fraction measurements of only one fluid layer at a time. To overcome this challenge, a multi-tracer PLIF approach has been developed. With multiple PLIF tracers, it is possible to resolve the volume fraction of multiple components in a mixture simultaneously. This presentation focuses on the application and challenges of using two PLIF tracers in gases. Specifically, acetone and anisole are used as fluorescent tracers. Acetone excited by 266 nm UV light will emit fluorescence across a broad band peaking around 410 nm, and anisole excited by the same 266 nm will fluoresce at a narrowband 295 nm. Such is demonstrated through a three-layer Rayleigh-Taylor driven mixing study. The mixing is being generated in a blown-down three-layer gas tunnel, by blowing a lighter air-helium mixture in between two heavier air layers. In this presentation, a comparison of tracers is made, and the conflicts that arise from their simultaneous use are discussed in detail. This includes spectral-conflicts such as tracer crosstalk, fluorescence reabsorption, and tracer-tracer collisional quenching. This work contributes to the advancement of diagnostics in gas mixing and opens new avenues of research for multi-component/variable density mixing.