Molecular Tagging Velocimetry (MTV) in gases
MTV is a laser spectroscopy technique that was pioneered by NASA. It relies on the tagging and tracking of molecular probes. It is therefore particularly adapted to measurements in very high and low-speed flows where seeding with particles (like for PIV or LDV) is challenging.
Our system is transportable and has down a couple of cross-country trips already! The tunable dye laser has been customized to enable a dual pulse capability for velocimetry. So far we have tested N2O and H2O tracers successfully in a broad range of temperatures and pressures.
Main publications
MM TAREQ, C FORT, R CAPANNA, MJ YAMAKAITIS, R AZMY, K MCDANIEL, and PM BARDET. Near-wall hydroxyl tagging velocimetry around a high-Reynolds number airfoil, AIAA SciTech, Orlando, FL, Jan. 8-12 2024 https://arc.aiaa.org/doi/abs/10.2514/6.2024-2327
MA ANDRE, PM BARDET, RA BURNS, PM DANEHY, S. CADELL, and B. WOODS. Development of N2O-MTV for low-speed flow and in-situ deployment to an integral effect facility. Experiments in Fluids. 59:14, https://doi.org/10.1007/s00348-017-2470-3 (2018).
MA ANDRE, PM BARDET, RA BURNS, and PM DANEHY. Hydroxyl Tagging Velocimetry for low velocity flows. Measurement Science and Technology. 28(8):085202, https://doi.org/10.1088/1361-6501/aa7ac8 (2017).
MTV in aqueous solutions
We have extended our work on MTV to liquids. We have been working on two schemes to generate the signals.
Main publications
C FORT and PM BARDET. Rhodamine-based caged dye for aqueous MTV with green lasers. Experiments in Fluids. 62:201, https://doi.org/10.1007/s00348-021-03303-7 (2021).
C FORT and PM BARDET. Efficient photobleaching of rhodamine 6G by a single UV pulse. Applied Optics. 60(22):6342-6350, https://doi.org/10.1364/AO.431209 (2021).
Fine pattern generation for MTV
One of the main limitations of MTV has been the ability to generate 2D patterns. We have been working on a scheme to generate fine 2D patterns.
We make use of the optical Talbot effect, a near-field diffraction phenomenon, to generate an array of quasi-parallel beamlets with very flexible beam spacing and diameter. Both pitch and width have been demonstrated down to the order of 10 μμm, which is about ten times smaller than that performed in previous MTV studies. Structured illumination with the Talbot effect (TESI) has the potential for even smaller sizes.
Main publication
C FORT, MA ANDRE, H PAZHAND, and PM BARDET. Talbot-effect structured illumination: pattern generation and application to long-distance μ-MTV. Experiments in Fluids. 61(2):1-21, https://doi.org/10.1007/s00348-019-2870-7 (2020).