A new measurement method for continuous detection of bed forms in movable bed laboratory experiments is presented and tested, which allows to measure bed forms during morphodynamic experiments, making use of a line laser and a 3-D camera. We conclude that the absolute measurement error increases with increasing flow velocity, its standard deviation increases with water depth and flow velocity, and the percentage of missing values increases with water depth. The quality of the data remains high when a robust LOESS filter is used. This is promising for bed form tracking applications in laboratory experiments, especially when lightweight sediments like polystyrene are used, which require smaller flow velocities to achieve dynamic similarity to the prototype.
Findings and implications to practice
The use of a line laser scanner system in combination with the application of suitable filtering technique, allows for quick monitoring of the bed at high accuracy in moving bed laboratory experiments.
As example result, the right colour plot shows the measured bed level (unfiltered) as well as the longitudinal and transverse bed profile along the black lines. For the profile data, blue dots indicate raw measurements, whereas red curves show the filtered results. The top half shows the results for experiment 4 (sand) and the bottom half for experiment 5 (polystyrene). Source: (Figure 10, de Ruijsscher et al. 2018)
de Ruijsscher, T. V., Hoitink, A. J. F., Dinnissen, S., Vermeulen, B., & Hazenberg, P. (2018). Application of a Line Laser Scanner for Bed Form Tracking in a Laboratory Flume. Water Resources Research, 54(3), 2078–2094. https://doi.org/10.1002/2017WR021646.
- de Ruijsscher, T.V., Dinnissen, S., Vermeulen, B., Hazenberg, P. Hoitink, A.J.F. (2016). Dune and alternate bar detection in a laboratory flume using a 3D laser scanner. In: G. Constantinescu, M. Garcia, D. Hanes (Eds.), Proceedings of the International Conference on Fluvial Hydraulics (River Flow 2016), 11-14 July, 2016, St. Louis, USA, pp. 379-380.
- Here is also available the list of related conference abstracts and (under)graduate thesis with progress results of the main researcher or contributors to this project.
The supporting dataset of the the flume experiment and the Matlab scripts to process line laser scanner data and to perform statistical analysis. https://dataverse.nl/dataset.xhtml?persistentId=hdl:10411/YACJ6D.
Model or tool access
The numerical implementation of the LOESS algorithm in Matlab and C++ is open source and can be found on https://github.com/bartverm.
Morphological patterns at the intake of a side channel over an oblique sill
Qualitative comparison of the river bed dynamics in the side channel of the longitudinal dam and the flat bed conditions in the scale model at low water level.
05/09/2018 by Timo de Ruijsscher et al.
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Last modified: 29/01/2019