Journal of Hydraulic Engineering

This paper provides a quantitative comparison of a benchmarking dam-break case simulated by a particle method. The velocity comparison is usually absent in particle-method simulation, but both the water surface and velocity distribution are presented in this study. Various velocity profiles are shown at different sections located either upstream or downstream of the gate position of the initial water column. The effects of a turbulence model and particle size are then discussed to show the necessity of using a turbulence model in particle method. The comparisons show good agreement in both the water surface profiles and velocity distributions. The utilization of turbulence model and roughness coefficient in moving particle Semiimplicit (MPS) method improves the velocity distribution compared with the standard MPS method. A quantitative comparison of velocity distribution on the basis of relative root mean squared error (RRMSE) value was also executed to show the capacity of MPS method in simulating fluid flow. This study indicates that the particle method is capable of reproducing both the velocity distribution and water surface in a dam-break simulation.

Complex and/or large size water distribution networks (WDNs) require the division of the hydraulic system into modules to simplify the analysis and the management tasks. In the modern science of networks, the modularity index has been proposed to detect communities, i.e., groups/clusters of nodes characterized by stronger interconnections. The modularity index is a measure of the strength of the network division into communities and it is maximized to identify them. Therefore, the division into modules of WDNs, also named segmentation, could be performed by using the modularity index as metric to identify cluster of nodes. Nevertheless, modularity index needs to be revised considering the specificity of the hydraulic systems, which are infrastructure networks. In fact, the division into modules for infrastructure networks, although it can be based on the identification of clusters of nodes, is not aimed at investigating network features. Differently, the aim is the practical issue of simplifying system analysis, planning and management; therefore, the division is constrained by the technical needs. Accordingly, in the present work the classic modularity index is firstly presented. Successively, it is tailored and modified for WDNs. Furthermore, a MO strategy for optimal segmentation is presented and discussed also using a real test network. The optimization framework is based on the maximization of the WDN-oriented modularity-based index versus the minimization of the cost of newly installed devices to obtain network segments. Those are a set of optimal divisions into modules of the hydraulic system which are the basis for an integrated, dynamical planning.

Archimedes screw generators (ASGs) are beginning to be widely adopted at low-head hydro sites in Europe due to their high efficiency, competitive costs, and low environmental impact. ASGs are particularly appropriate for low-head sites. Power is transferred from a water flow to an Archimedes screw by the distribution of static pressure produced by the water volumes between the flights of the screw. Two theoretical models based on quasi-static pressure analysis are developed to predict the performance of ASGs. The first model uses idealized geometry, while the second incorporates the geometric properties of a rotating Archimedes screw, including slope, pitch, and inner and outer diameter. The second model was also formulated to simulate the performance of Archimedes screws operating across a full range of fill levels from empty to overfull. Both models predict that if all friction losses and entry and exit effects are neglected, the Archimedes screw can convert all potential energy in a water flow into mechanical power. Including gap leakage effects in the simulation decreases efficiency. A new leakage model is used because the current standard leakage model is only appropriate for screws in a full condition. It was confirmed that the maximum efficiency of an ASG will occur when the screw is operating near full; however, reasonable efficiencies are maintained if the screw is either overfilled or underfilled. The model predictions were consistent with the measured performance of a laboratory-scale Archimedes screw at low rotational speeds.

Modelling floods in urban areas generally requires the modelling of both surface and subsurface flows, along with the exchange discharges between these flows. These latter exchanges are studied on an experimental facility at the Ujigawa Open Laboratory of Kyoto University representing a typical urban drainage system with a single street connected through inlets to a drainage pipe located underneath. An exchange model is developed for the cases in which exchange flows are pressurized, applying a head balance between the surface and subsurface layers and using common head loss formulae. Results of the exchange model agree with experimental measurements and show that, for this experimental setup, the exchanges cannot be modelled by fitting a simple and commonly used orifice-type equation. A hydrodynamic model coupling the one-dimensional (1D) and two-dimensional (2D) shallow water equations for, respectively, the pipe and the street flows and including the analytical exchange model is used to simulate the experimental flows. The numerical model can simulate the global characteristics of both street and pipe flows but shows some discrepancies concerning local perturbations of street flow because of the exchange processes.

Vertical slot fishways are a type of fish pass of wide operating range that allow fish to move across obstacles in rivers. This study aims to model the performance of these structures, under uniform and nonuniform flow conditions, using discharge coefficients involving the downstream water level together with a logical algorithm. This will allow an explanation of the hydraulic behavior of this type of fishway under tailwater levels and flow variations on rivers. Two vertical slot fishways located in Duero River (North-Central Spain), subject to different hydraulic conditions, were studied for the validation of the proposed formulation. The observed values are consistent with the predicted results and, among others, demonstrate the importance of including variables that consider downstream water level. Consequently, the proposed discharge coefficients together with the algorithm have resulted in a method that enables the improvement of the performance of both existing and future vertical slot fishways. This will have major implications in real-life scenarios in which uniform operation conditions are rarely achieved.