Work

Free-surface measurements in a cylindrical container using synthetic schlieren with extended paraxial range

Year: 2026

Type: article

Abstract: In this study, the free-surface synthetic schlieren (FS-SS) method, as proposed by Moisy et al. ( Exp. Fluids 46 (2009) 1021), is extended to allow a wider application of the method. The reliance on small-angle paraxial approximation is removed, which allows for shorter distances of the camera to the free surface. Also, the presence of walls and non-constant depth of the liquid layer are accounted for. The difference between the original and modified approach is evaluated using a ray tracing approach. The extension of the method is demonstrated with measurements of the water surface in a cylinder for both rotating and non-rotating cases, i.e., surface waves due to impact, a surface depression due to a spin-up vortex, and the parabolic free surface in a rotating cylinder. The measured variations in surface elevation are as small as $$\mathcal {O}$$ O (10 $$\upmu $$ μ m) with a range in paraxial angle up to ±0.56 rad ( $${32.3}^\circ $$ 32.3 ∘ ).

Source: Experiments in Fluids

DOI: 10.1007/s00348-026-04240-z

Authors: Lyke E. van Dalen, Jan-Bert Flór, Jerry Westerweel

Institutions: Delft University of Technology, Institut polytechnique de Grenoble, Centre National de la Recherche Scientifique, Laboratoire des Écoulements Géophysiques et Industriels, Université Grenoble Alpes

Language: English

Topic: Optical measurement and interference techniques

Subfield: Computer Vision and Pattern Recognition

Field: Computer Science

Domain: Physical Sciences

Open Access status: hybrid

Estimated APC paid: $2,590

Funder: European Research Council