Scour holes are large, local perturbations in the river bed. They have been observed all over the world, for example in the Mahakan river in Indonesia (Vermeulen et al., 2014), the Mississippi river in the Unites States (Nittrouer et al., 2011), and in the Rhine-Meuse Estuary in the Netherlands (Huismans et al., 2021). The deep scour holes with their steep slopes can pose a threat to nearby infrastructure. To illustrate, in the Common Meuse (Grensmaas) in Limburg (the Netherlands) more than 15 deep scour holes were formed during the summer flood in 2021 (Barneveld et al., 2022). One of these scour holes uncovered a pipeline requiring a new pipeline to be installed. Another threatened the stability of a ferry landing (see Figure 1), resulting in a temporarily stop of the ferry service (Task Force Fact-finding hoogwater 2021, 2021).
To estimate potential threats of scour holes, a good understanding of their behaviour is required. In previous years, a lot of research has been done in understanding the formation of scour holes. These studies have shown that the formation of a scour hole is determined by the flow characteristics and the composition of the bed. With flume experiments the formation of a scour hole was reproduced on a small scale (e.g. Uijttewaal et al., 2016). These experiments have shown that the flow in a scour hole is highly three-dimensional. However, it is still unclear how the complex 3D flow processes affect the behaviour of a scour hole on the long term and how the intensity of these flow processes is related to the upstream discharge. One way to better understand the flow processes is to simulate the processes with a numerical model. A common method is Computational Fluid Dynamics (CFD) (see Figure 2). In addition, we are likely to measure flow velocities in a scour hole in the field. This data can be used to validate the numerical model.
The aim of this research is to describe the important 3D flow processes in a scour hole. For this purpose, a numerical model will be established to simulate the 3D flow processes in a scour hole. The results of the simulations will help to understand the complex 3D flow processes in a scour hole and their contribution to the behaviour of a scour hole on the long term.
The research can be divided into the following steps:
- Modify an existing 2D hydrodynamic OpenFoam model for sand wave to scour hole applications and validate based on existing data of flow patterns.
- Setting up a 3D hydrodynamic CFD model based on the 2D hydrodynamic OpenFOAM model. This 2D model will be extended to a 3D model.
- Analysing the intensity of the flow processes in a scour hole under varying discharges using the numerical model.
The start of the MSc thesis should be in February 2025 or later. Course preparation can start from December 2024.
References
- Barneveld, H., Hoitink, A. J. F., & Frings, R. M. (2022). Massive morphological changes during the 2021 summer flood in the River Meuse. NCR days 2022.
- Bom, S., Huismans, Y., NG, J., & Uijttewaal, W. (2018). Scour holes in heterogeneous subsoil: A numerical study on hydrodynamic processes in the development of the scour holes. NCR days 2018: The Future River, Deltares.
- Huismans, Y., Koopmans, H., Wiersma, A., de Haas, T., Berends, K., Sloff, K., & Stouthamer, E. (2021). Lithological control on scour hole formation in the Rhine-Meuse Estuary. Geomorphology, 385. https://doi.org/10.1016/j.geomorph.2021.107720
- Nittrouer, J. A., Mohrig, D., Allison, M. A., & Peyret, A. P. B. (2011). The lowermost Mississippi River: a mixed bedrock‐alluvial channel. Sedimentology, 58(7), 1914-1934. https://doi.org/10.1111/j.1365-3091.2011.01245.x
- Task Force Fact-finding hoogwater 2021. (2021). Hoogwater 2021 Feiten en Duiding. E. N. Waterveiligheid.
- Uijttewaal, W., huismans, Y., & Koopmans, H. (2016). A scaled experimental pilot-study on deep scour holes in river beds of heterogeneous composition.
- Vermeulen, B., Hoitink, A. J. F., van Berkum, S. W., & Hidayat, H. (2014). Sharp bends associated with deep scours in a tropical river: The river Mahakam (East Kalimantan, Indonesia). Journal of Geophysical Research: Earth Surface, 119(7), 1441-1454. https://doi.org/10.1002/2013jf002923
Supervision
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