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.

In open channel networks, flow is usually approximated by the one-dimensional (1D) Saint-Venant equations coupled with an empirical junction model. In this work, a comparison in terms of accuracy and computational cost between a coupled 1D-2D shallow water model and a fully two-dimensional (2D) model is presented. The paper explores the ability of a coupled model to simulate the flow processes during supercritical flows in crossroads. This combination leads to a significant reduction in the computational time, as a 1D approach is used in branches and a 2D approach is employed in selected areas only where detailed flow information is essential. Overall, the numerical results suggest that the coupled model is able to accurately simulate the main flow processes. In particular, hydraulic jumps, recirculation zones, and discharge distribution are reasonably well reproduced and clearly identified. Overall, the proposed model leads to a 30% reduction in run times.

In this paper, a comparison between the 1D and 2D approaches for simulating combining flows at open-channel junctions is presented. The two approaches are described allowing for a full comprehension of flow modelling. For flows in an open-channel network, mutual effects exist among the channel branches at a junction. Therefore, the 1D Saint-Venant equations for the branch flows are supplemented by various junction models. The existing models are of empirical nature and depend on the flow regime and thus are not practical in all cases. The numerical approximation of the two approaches is performed by the Runge–Kutta discontinuous Galerkin scheme and tested using defined flow problems to illustrate the results of the two approaches. Comparisons are conducted for supercritical, transitional and subcritical flows, indicating the validity range of the 1D approach and the advantages of the 2D approach.

The spectrum of this survey turns on the evaluation of some eminent Riemann solvers (or the so-called solver), for the shallow water equations, when employed with high-order Runge–Kutta discontinuous Galerkin (RKDG) methods. Based on the assumption that: The higher is the accuracy order of a numerical method, the less crucial is the choice of Riemann solver; actual literature rather use the Lax-Friedrich solver as it is easy and less costly, whereas many others could be also applied such as the Godunov, Roe, Osher, HLL, HLLC, and HLLE. In practical applications, the flow can be dominated by geometry, and friction effects have to be taken into consideration. With the intention of obtaining a suitable choice of the Riemann solver function for high-order RKDG methods, a one-dimensional numerical investigation was performed. Three traditional hydraulic problems were computed by this collection of solvers cooperated with high-order RKDG methods. A comparison of the performance of the solvers was carried out di...

Classically, in open-channel networks, the flow is numerically approximated by the one-dimensional Saint Venant equations coupled with a junction model. In this study, a comparison between the one-dimensional (1D) and two-dimensional (2D) numerical simulations of subcritical flow in open-channel networks is presented and completely described allowing for a full comprehension of the modeling of water flow. For the 1D, the mathematical model used is the 1D Saint Venant equations to find the solution in branches. For junction, various models based on momentum or energy conservation have been developed to relate the flow variables at the junction. These models are of empirical nature due to certain parameters given by experimental results and moreover they often present a reduced field of validity. In contrast, for the 2D simulation, the junction is discretized into triangular cells and we simply apply the 2D Saint Venant equations, which are solved by a second-order finite-volume method. In order to give an ...

Hydrodynamic modelling is used to analyse the inundation behaviour of Sidi Bel Abbes city (North-West of Algeria) during extreme flood events. The study reach, 5.4 km in length, is a section of Wadi Mekerra through Sidi Bel Abbes city. Land and bathymetric surveys were used to create a digital terrain model (DTM) of the river channel and the floodplain. By coupling the geometry with hydrologic data, a two dimensional hydrodynamic model was built. The model is based on integrating Saint-Venant shallow waters (depth averaged) equations through Runge–Kutta discontinuous Galerkin numerical scheme. It was calibrated in terms of roughness coefficients on measured values of water surface elevation and discharge registered in the Sidi Bel Abbes gauging station. The objective is to draw the flood maps under extreme river flood event. The results are helpful for local authorities in order to take the appropriate defence measures in the future.