Wervelend water

Civil Engineering and Geoscience

Horizontal mixing in shallow flows

Shallow shear flows play an important role in the transverse transport of mass and momentum in rivers. In order to understand structure of the flow and the mechanism resulting in the particular turbulence properties, three types of shallow mixing layers are investigated each with a different cause for the velocity difference: inflow conditions, bed level and bed roughness. It is shown that mixing layer properties are highly affected by the 3D turbulence generated in the bottom boundary layer. This implies that effects of subtle geometric properties like roughness variation and bed level changes should be incorporated in predictive modelsHydraulic EngineeringCivil Engineering and Geoscience

Turbulente ondiepe stromingen

Hydraulic EngineeringCivil Engineering and Geoscience

Numerical and physical modelling of rapidly varying flow over weir-like obstacles in rivers and floodplains

Hydraulic EngineeringCivil Engineering and Geoscience

Flow resistance of vegetated oblique weir-like obstacles during high water stages

At high water stages obstacles in the flood plains of a river contribute to the flow resistance and hamper the conveyance capacity. In particular the elevated vegetated parts are expected to play an important role. The objective of this research work is to determine the form drag due to vegetated oblique weir-like obstacles. The experiments have been performed to measure the energy head losses for a range of subcritical flow conditions, varying discharges and downstream water levels. The energy head loss caused by the submerged vegetated weir-like obstacle has been modeled using an expansion loss form drag model that has been derived from one dimensional momentum conservation equation and accounts for the energy loss associated with a deceleration of the flow downstream of a sudden expansion. The results have been compared with the experimental data and showed an overall good agreement.Hydraulic EngineeringCivil Engineering and Geoscience

Flow resistance of vegetated oblique weir-like obstacles during high water stages

At high water stages obstacles in the floodplains of a river contribute to the flow resistance. In particular the elevated vegetated parts are expected to play an important role. The objective of this study is to estimate and parameterize the form drag due to vegetated oblique weir-like obstacles. An experimental study has been carried out in the Laboratory of Environmental Fluid Mechanics of Delft University of Technology. Measurements for energy head losses were carried out for a range of discharges and downstream water levels covering submerged and subcritical flow conditions. The Head loss due to submerged vegetated dikes has been modeled by an expansion loss form drag model. Expansion loss form drag model has been derived from one dimensional momentum conservation equation and accounts for the energy loss associated with a deceleration of the flow downstream of a sudden flow expansion. The results have been compared with experimental data.Hydraulic EngineeringCivil Engineering and Geoscience