Author(s): A. De Loor; T. O’Mahoney; W. C. D. Kortlever

Linked Author(s): Alexander De Loor

Keywords: Weir; CFD; Supercritical flow; Bed protection

Abstract: On the 29th of December 2016, a ship carrying benzene collided with the weir near the city of Grave, The Netherlands. The impact caused significant damage to the weir and resulted in partial drainage of the upper reach. After an initial analysis of high water levels during river floods, Rijkswaterstaat decided to build a temporary dam downstream to partially block the flow through the weir. Thus, the upstream water levels could be restored and room was created to repair the damage. However, the partial closing meant that the entire river discharge was forced through the remaining section, less than half of the total width of the weir. This paper discusses the numerical simulations which were performed to approximate the flow conditions in that remaining section and to roughly predict the flow velocities which could occur during critical conditions. As it became apparent that simple weir discharge formula would not be sufficient, the choice was made to use a three-dimensional Computational Fluid Dynamics (CFD) Model. Because of time constraints, the model setup was relatively simple and a sensitivity analysis could not be performed. Nevertheless, the model gave an insight into the expected flow patterns up-and downstream of the weir and a more detailed estimation of the flow velocities near the bed than the models used in the river flood calculations (performed with WAQUA (WAQUA 2018) ). From the results, it was concluded that extra bed protection was necessary. At the same time, a question arose about how well the numerical model could simulate supercritical and subcritical flows as well as transitions between the two flow regimes.

DOI: https://doi.org/10.15142/T3TS8R

Year: 2018