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Abstract

A meshless and binless approach to compute statistics in 3D ensemble PTV We propose a method to obtain super-resolution of turbulent statistics for three-dimensional ensemble particle tracking velocimetry (EPTV). The method is “meshless” because it does not require the definition of a grid for computing derivatives, and it is “binless” because it does not require the definition of bins to compute local statistics. The method combines the constrained radial basis function (RBF) formalism introduced Sperotto et al. (Meas Sci Technol 33:094005, 2022) with an ensemble trick for the RBF regression of flow statistics. The computational cost for the RBF regression is alleviated using the partition of unity method (PUM). Three test cases are considered: (1) a 1D illustrative problem on a Gaussian process, (2) a 3D synthetic test case reproducing a 3D jet-like flow, and (3) an experimental dataset collected for an underwater jet flow at Re= 6750 using a four-camera 3D PTV system. For each test case, the method performances are compared to traditional binning approaches such as Gaussian weighting (Agüí and Jiménez in JFM 185:447–468, 1987), local polynomial fitting (Agüera et al. in Meas Sci Technol 27:124011, 2016), as well as binned versions of RBFs Two-dye two-color LIF spectroscopy on droplets of water/ethanol mixtures for measurement of temperature and composition In this seminar we will present a two-color laser-induced-fluorescence (2c-LIF) technique based on a two-dye mixture, which is applied in a droplet chain of ethanol, water and ethanol/water mixtures. The technique is optimized in order to reach a high-temperature sensitivity and to avoid the detection of lasing effects in the droplets. Various droplet sizes are studied in regard to the limitation of the detection system for small micrometric droplets. The breakup of a liquid jet is analyzed to assess the technique in applications with liquid structures of different sizes. Additionally, a proposal is presented to expand the 2c-LIF application for studying ethanol/water droplets regarding mixture composition with a third color channel. Measurements in various ethanol/water mixtures are evaluated to show this possibility.