Sensitivity analysis of urban flood flows to hydraulic controls

Water Qualit

1d/2d porosity model for urban flood modeling

International audienc

Prediction of suspended sediment concentrations in river flows

Studying the suspended sediments concentration (SSC) is of critical interest for water management. However, acquiring information on suspended sediment concentration (SSC) through direct in situ measurements has always been a challenging task due to technical difficulties especially in flows where the character of suspended materials changes frequently. Ideally, researchers would like to be able to measure the suspended-sediment concentration at all points in a given river. Regarding the cost in terms of material and labor time, they simplify the task to the measurement at all points in a cross section, the measurement along one vertical or even the measurement at one point. Each time the procedure includes a smaller portion of the river, spatial error becomes grater. Regarding all these difficulties, numerical modeling is used instead of or coupled with in situ measurement to optimize the cost of studying suspended sediments concentration. Various numerical and analytical formulas of different order of complexity are used to represent SSC, and knowing the complexity of transport in rivers, it is still impossible to have a universal profile. In this context, we are interested into establishing an innovative model to predict SSC in river flows. The model suggested in the present study is obtained by combining the properties of the sediment diffusivity coefficients of the parabolic constant model and of the model presented by Itakura and Kishi (1980). The model established is validated with a range of experimental data

Experimental investigation and performance analysis of Archimedes screw generator

The generation of renewable energy with Archimedes screw generators (ASG) transforming potential energy of fluid flow into mechanical energy is a growing technology suitable for low-head hydraulic sites. This paper presents an improved theoretical model linking screw performance to screw geometry and flow conditions. This model takes into account leakages, friction losses and variable fill levels. The modelled values of torques and efficiencies are in a fairly good agreement with experimental results obtained for a laboratory-scale screw. The downstream screw immersion is shown to impact ASG efficiency and an optimal immersion level is proposed. It has been found that fluid friction on the screw is not negligible. The analysis shows that a single value of the friction coefficient is suitable for modelling the screw performance under various flow conditions. The leakage phenomenon at under-filling flow conditions and friction forces in complex turbulent flows need to be further studied

Le transport solide : du réseau hydrographique au réseau urbain

Mécanique des fluide

Etude d'un ecoulement diphasique disperse. Developpement de methodes de mesures de la concentration de la phase liquide

SIGLEINIST T 73121 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Modeling sediment deposition from marine outfall jets

International audienceThis paper presents a two-dimensional model to study the sediment deposition from marine outfall jets. The introduced unidirectional coupling (fluid-sediment) is an appropriate choice in the case of low-concentrated particle-laden jets such as municipal wastewater discharge, where the concentration of particles is small enough and does not affect the hydrodynamic development of the jet in the nearfield. The sedimentation model takes advantage of the preferential concentration phenomenon. The deposition criterion states that the deposition of sediments begins when the vertical component of the entrainment velocity becomes smaller than the settling velocity. Once the deposition process begins, it is controlled by the settling velocity, entrainment velocity, volume flux, and sediment concentration. The deposition along the jet trajectory is expressed by an ordinary differential equation coupled with the liquid phase equations. Experiments of Lane-Serff and Moran [Sedimentation from Buoyant jets. J Hyd Eng. 2005;131(3):166-174], Cuthbertson and Davies [Deposition from particle-laden, round, turbulent, horizontal, buoyant jets in stationary and coflowing receiving fluids. J Hydr Eng. 2008;134(4):390-402], and Lee [Mixing of horizontal sediment laden jets [dissertation]. Hong Kong: University of Hong Kong; 2010], chosen from bibliography, are used to validate the model. These experiments cover the cases of horizontal and inclined buoyant jets in stationary ambient, horizontal buoyant jets in co-flow current and nonbuoyant horizontal jets in stationary ambient. Good agreement between the experiments and the obtained simulations is revealed