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Reservoir sedimentation can represent a major threat to water supply and should be considered when establishing a reservoir's design life. This study optimized reservoir management using a Dynamic Programming Neural Network by incorporating an optimal operation rule devised to minimize the gap between water releases and water irrigation demands. The Foum El-Gherza Dam in Algeria was selected to validate the proposed optimization model. The optimized dredging model saved large quantities of water from April to October (dry summer season), economizing a total of 10.25 million m3 or 9% more water over a 4 year period. Dredging increased the satisfaction rate of water demand from 16% (historical releases) to 44% (optimized releases), while a satisfaction rate of 34.75% (optimized releases) was obtained in the case of no-dredging. The operation rule generated from the dredging operation proved to be more reliable, more resilient and less vulnerable to satisfy water demand patterns on a monthly basis. Finally, the dredging operation's optimal releases were superior to that obtained in the no-dredging operation case demonstrating that dredging is an effective solution to tackle reservoir sedimentation if it is incorporated as part of a holistic dam management strategy. However, optimized releases obtained during venting were inferior to those of the no-venting case due to the excess water releases required for venting. This study provides practical information on the extent of modelling applications for future perspectives on the need for advanced reservoir sedimentation management. [ABSTRACT FROM AUTHOR]

Bridge pier scour was simulated by a coupled fully 3D hydro-morphodynamic model and validated against 24 experimental datasets for a combination of different pier shapes, approach velocities and sediment bed material. The proposed numerical model adopts an Eulerian multi-fluid model to account for rolling and saltating particles and computes bed shear stresses from implicit wall functions. ANSYS Fluent solved the continuity and Navier-Stokes equations, closed by the RSM turbulence model, which were coupled with sediment transport submodels by source terms. Numerical instabilities were addressed in the sediment transport submodels which were ascribed to the fine mesh resolution required to resolve the crucial horseshoe vortex and the diffusion resulting from the discretization of the Immersed Boundary method. [ABSTRACT FROM AUTHOR]

Liu's theory of 1957 to estimate the point of incipient motion, derived assuming a flat bed slope and uniform flow, states that for large particles the movability number (defined as the ratio of the shear velocity to the settling velocity), is constant. Data collected from 12 undistorted and unscaled laboratory tests was used to investigate the applicability of the theory on steep riprap slopes. The tests indicate that the dimensionless movability number (MN) is constant for large particle Reynold numbers. For design purposes, the recommended movability number which emerged from this study is 0.18, provided that the steep bed slope is taken into account, the energy slope is considered in MN, and that the theoretical settling velocity is calculated using an accurate drag coefficient and the d90 sieve size of the riprap. [ABSTRACT FROM AUTHOR]

Particle image velocimetry scalar measurements were carried out on the body of a stably stratified density current with an inlet Reynolds number of 2,300 and bulk Richardson number of 0.1. These measurements allowed the mass and momentum transport between the current and the less dense ambient fluid to be investigated. Reynolds stress, Reynolds flux, and shear production of turbulent kinetic-energy profiles revealed local maxima at the bed, as well as at the interface with the ambient fluid. Profiles of excess density variance and buoyancy production of turbulent kinetic energy revealed only local maxima at the interface with the ambient. These maxima decreased downstream as the stable density gradient reduced the turbulent intensities, until turbulence collapsed. A two-dimensional, unsteady, Reynolds-averaged Navier-Stokes (2DV-URANS) simulation was also performed on this density current. Good agreement was found between the modeled and measured normalized mean flow profiles. A comparison was also made between the measured and modeled outer flow scales of the density current. [ABSTRACT FROM AUTHOR]