Modeling the hydrodynamic interactions between the river morphology and navigation channel operations

Abstract

The Nile River is the main route for inland navigation in Egypt. The vessels navigating through inland waterways generate complex physical forces that need to be studied extensively. Quantifying the effects of vessels sailing along a waterway is a complex problem because the river flow is unsteady and the river bathymetry is irregular. This paper aims to investigate the hydrodynamic effects resulting from the movement of vessels such as return currents around the vessel, the draw down of the water surface, under keel clearance, and the shear stress induced by vessels operating in the Nile River. Modeling such effects has been performed by applied the two-dimensional ADH (adaptive hydraulics) model to a river reach for different navigation channel operation scenarios. The obtained results show that the draw down heights, the water fluctuation, and the shear stress magnitude are larger when the river cross sectionals are narrow and the shallow water depths. These river sections are considered more disposed to bed erosion and it is morphologically unsafe. The section having the narrowest width and the lowest depth was associated with the largest drawdown percentages of 98.3% and 87.3% in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least drawdown percentages of 48.5% and 51.9% in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was associated with the largest fluctuations of 22.0 cm and 41.9 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was associated with the least fluctuations of 0.6 cm and 1.8 cm in one-way and two-way scenarios. The section having the narrowest width and the lowest depth was the worst section for under keel clearance of 5.0 cm and 33.3 cm in one-way and two-way scenarios. While the section having the widest width and the largest depth was the best section, where its clearance values were 183.2 cm and 155.0 cm in one-way and two-way scenarios. It is concluded that a numerical model is a valuable tool for predicting and quantifying the hydrodynamic effects of vessels moving through a two-dimensional flow field and can be used to evaluate different scenarios that are difficult to measure in the field or a physical model. Also, it provides visualization products that help us understand the complicated forces produced by vessels moving in a navigation channel.