Author(s): Giovanni De Cesare; Anton Schleiss
Linked Author(s): Anton J. Schleiss
Keywords: Turbidity currents; Reservoir sedimentation; Sediment transport; Physical modelling; Numerical modelling; Ultrasonic Doppler velocimetry; Instantaneous measurement; Flow mapping; Velocity profile measurement; Suspension
Abstract: All lakes created on natural rivers are subjected to sedimentation. Their dead storage, designed to accumulate the sediment yield, is in some particular cases nearly filled. This can cause exploitation problems or even affect the operation of the bottom outlet. In order to clarify the flow mechanism and the sediment transport of river-induced turbidity currents in artificial lakes, physical modelling of turbidity currents was carried out in a laboratory flume. Parallel to the laboratory study, field observations were made in an alpine reservoir and its main inflow river. The turbidity currents in the laboratory were monitored using ultrasound probes functioning with the Doppler Method, thus giving a complete velocity profile along the ultrasound beam in a very short time. The flow in the laboratory flume was simulated numerically. The results of the laboratory experiments and the numerical calculations were compared in order to check the accuracy of the numerical two-phase flow code. Comparisons were made with vertical and axial velocity profiles. The complete 3D-flow field was computed and compared with the measured 2D-velocity distribution near the bottom of the flume. The so-tested numerical two-phase flow code was then used to simulate river-induced turbidity currents directly in an existing geometry.