https://doi.org/10.1140/epje/s10189-024-00413-y
Tips and Tricks - Flowing Matter
Modeling and correction of image drift in dynamic shadowgraphy experiments
1
Dipartimento di Fisica“A. Pontremoli”, Università degli Studi di Milano, Milan, Italy
2
Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano, Segrate, Italy
3
LFCR UMR5150, E2S UPPA, CNRS, Universite de Pau et des Pays de l’Adour, Anglet, France
Received:
2
December
2023
Accepted:
3
March
2024
Published online:
8
April
2024
The study of phoretic transport phenomena under non-stationary conditions presents several challenges, mostly related to the stability of the experimental apparatus. This is particularly true when investigating with optical means the subtle temperature and concentration fluctuations that arise during diffusion processes, superimposed to the macroscopic state of the system. Under these conditions, the tenuous signal from fluctuations is easily altered by the presence of artifacts. Here, we address an experimental issue frequently reported in the investigation by means of dynamic shadowgraphy of the non-equilibrium fluctuations arising in liquid mixtures under non-stationary conditions, such as those arising after the imposition or removal of a thermal stress, where experiments show systematically the presence of a spurious contribution in the reconstructed structure function of the fluctuations, which depends quadratically from the time delay. We clarify the mechanisms responsible for this artifact, showing that it is caused by the imperfect alignment of the sample cell with respect to gravity, which couples the temporal evolution of the concentration profile within the sample with the optical signal collected by the shadowgraph diagnostics. We propose a data analysis protocol that enables disentangling the spurious contributions and the genuine dynamics of the fluctuations, which can be thus reliably reconstructed.
Stefano Castellini and Matteo Brizioli have contributed equally to this work.
© The Author(s) 2024
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