Stereo-PIV measurements within the canopy in open-channel flows
File(s)
Published version
Author(s)
Trevisson, Michele
Akutina, Yulia
Eiff, Olivier
Type
Journal Article
Abstract
Measuring the flow field not just above but also inside the canopy of rough beds in open-channel flows is challenging when optical access from below or the side is not possible. To this end, a new stereo-PIV arrangement was implemented and tested. To optically access the area in between the roughness elements, a top-viewing stereo-PIV system was installed at a steep viewing angle of 70◦ . Furthermore, a glass plate was installed at the water surface to avoid random image distortions
from surface waves. Finally, in-house-produced low-cost fluorescent particles were used to filter out laser reflections on the canopy’s surface. To validate the stereo-PIV measurements with respect to the steep viewing angle of the stereo cameras, the instantaneous flow field above a bed of spheres was measured simultaneously with the stereo-PIV system and with a third side-looking camera for standard 2D-PIV processing. Two different water depths and two different Reynolds numbers were investigated under uniform flow conditions. Finally, to assess the influence of the glass plate on the flow, 2D-PIV measurements were performed with and without the glass plate. It is shown that the steep viewing stereo PIV can properly reconstruct the instantaneous, mean and turbulent statistics except for the vertical normal turbulent stresses, which are overestimated due to peak-locking errors. Also, the boundary layer developing below the glass plate induces a slight acceleration in the bulk flow, which can be considered negligible for higher water depths. In all instances, the flow acceleration does not affect
the near-bed region.
from surface waves. Finally, in-house-produced low-cost fluorescent particles were used to filter out laser reflections on the canopy’s surface. To validate the stereo-PIV measurements with respect to the steep viewing angle of the stereo cameras, the instantaneous flow field above a bed of spheres was measured simultaneously with the stereo-PIV system and with a third side-looking camera for standard 2D-PIV processing. Two different water depths and two different Reynolds numbers were investigated under uniform flow conditions. Finally, to assess the influence of the glass plate on the flow, 2D-PIV measurements were performed with and without the glass plate. It is shown that the steep viewing stereo PIV can properly reconstruct the instantaneous, mean and turbulent statistics except for the vertical normal turbulent stresses, which are overestimated due to peak-locking errors. Also, the boundary layer developing below the glass plate induces a slight acceleration in the bulk flow, which can be considered negligible for higher water depths. In all instances, the flow acceleration does not affect
the near-bed region.
Date Issued
2024-05-01
Date Acceptance
2024-03-04
Citation
Experiments in Fluids, 2024, 65 (5)
ISSN
0723-4864
Publisher
Springer Science and Business Media LLC
Journal / Book Title
Experiments in Fluids
Volume
65
Issue
5
Copyright Statement
© The Author(s) 2024 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Publication Status
Published
Article Number
68
Date Publish Online
2024-04-18