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A direct spatial image correlation technique is presented for estimating the Lagrangian displacement vector from image pairs based on molecular tagging diagnostics. The procedure provides significant improvement in measurement accuracy compared to existing approaches for molecular tagging velocimetry (MTV) analysis. Furthermore, this technique is of more general utility in that it is able to accommodate other laser tagging patterns besides the usual grid arrangement. Simulations are performed to determine the effects of many experimental and processing issues on the sub-pixel accuracy of displacement estimates. The results provide guidelines for optimizing the implementation of MTV. Experimental data in support of this processing technique are provided.

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Abstract. This work reports our recent developments of novel techniques for velocimetry and studies of the Lagrangian evolution of mixing interfaces based on molecular tagging approaches. These developments take advantage of a class of newly engineered phosphorescent supramolecules that are water soluble. Previous implementations using photochromic molecules and caged fluorescein are briefly discussed and compared. The application of molecular tagging velocimetry is demonstrated in several flow fields, including examples which illustrate its capability in flows with significant out-of-plane motion and its potential for simultaneous passive scalar and velocity measurements.

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