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A vertical 2Dxzlaterally averaged hydrodynamic model is presented in this paper to study the aeration process in lakes. The system exhibits highly nonlinear behaviour due to the phenomena involved such as stratification, air concentration, and convective terms. The suggested model is used to simulate mechanical aeration to overcome and prevent the eutrophication in lakes. The multiquadric radial basis functions are used to solve numerically the governing partial differential equations. Because of the difficulty and the complexity when choosing a suitable shape parameter in radial basis functions, an alternative way is introduced in this work to overcome these difficulties. A validation study is carried out using several test examples, including Poisson, Navier–Stokes and transport equations. Finally, the proposed model is first applied to simulate a squared domain aeration problem and then a real test case has been considered. The obtained results are in good agreement with the results reported in the literature. [ABSTRACT FROM PUBLISHER]

Abstract: Water distribution system design belongs to a class of large combinatorial non-linear optimization problems, involving complex implicit constraints, such as conservation of mass and energy equations, which are commonly satisfied through the use of hydraulic simulation solvers. Recently, many researchers have shifted the focus from traditional optimization methods to the use of meta-heuristic approaches for handling this complexity. This paper proposes a hybrid particle swarm optimization (PSO) and differential evolution (DE) method, linked to the hydraulic simulator, EPANET, for minimizing the cost design of water distribution systems. The performance of the proposed PSO-DE algorithm is demonstrated using three well-known benchmark water distribution system problems, the two-loop network, the Hanoi network and the New York Tunnels network. The results are compared to that of standard PSO and previously applied optimization methods. It is found that PSO-DE is a promising method for solving water distribution system design problems as it outperforms standard PSO and other algorithms previously presented in the literature for the three case studies considered. [Copyright &y& Elsevier]

Abstract: We use velocities from 65 continuous stations and 31 survey-mode GPS sites as well as kinematic modeling to investigate present day deformation along the Africa–Iberia plate boundary zone in the western Mediterranean region. The GPS velocity field shows southwestward motion of the central part of the Rif Mountains in northern Morocco with respect to Africa varying between 3.5 and 4.0mm/yr, consistent with prior published results. Stations in the southwestern part of the Betic Mountains of southern Spain move west–southwest with respect to Eurasia (∼2–3mm/yr). The western component of Betics motion is consistent with partial transfer of Nubia–Eurasia plate motion into the southern Betics. The southward component of Betics motion with respect to Iberia is kinematically consistent with south to southwest motion of the Rif Mountains with respect to Africa. We use block modeling, constrained by mapped surface faults and seismicity to estimate the geometry and rates of strain accumulation on plate boundary structures. Our preferred plate boundary geometry includes one block between Iberia and Africa including the SW Betics, Alboran Sea, and central Rif. This geometry provides a good fit to the observed motions, suggesting a wide transpressive boundary in the westernmost Mediterranean, with deformation mainly accommodated by the Gloria–Azores fault system to the West and the Rif–Tell lineament to the East. Block boundaries encompass aspects of earlier interpretations suggesting three main deformation styles: (i) extension along the NE–SW trending Trans-Alboran shear zone, (ii) dextral strike-slip in the Betics corresponding to a well defined E–W seismic lineament, and (iii) right lateral strike-slip motion extending West to the Azores and right-lateral motion with compression extending East along the Algerian Tell. We interpret differential motion in the Rif–Alboran–Betic system to be driven both by surface processes related the Africa–Eurasia oblique convergence and sub-crustal dynamic processes associated with the long history of subduction of the Neotethys ocean lithosphere. The dextral slip identified in the Betic Mountains in Southern Spain may be related to the offshore fault that produced the Great 1755 Lisbon Earthquake, and as such may represent a significant seismic hazard for the West Mediterranean region. [Copyright &y& Elsevier]

The flow trough the Strait of Gibraltar could be analyzed as a problem of two-layer hydraulic exchange between the Atlantic ocean and the Mediterranean sea. The shallow water equations in both layers coupled together are an important tool to simulate this phenomenon. In this paper we perform an upwind schemes for hyperbolic equations based on the Roe approximate Riemann solver, to study the resulting model. The main goal assigned was to predict the location of the interface between the two layers. Therefore the computational results obtained are compared to previous results and experiments. [ABSTRACT FROM AUTHOR]

This paper investigates the effectiveness of the genetic algorithm (GA) evolved neural network for rainfall–runoff forecasting and its application to predict the runoff in a catchment located in a semi-arid climate in Morocco. To predict the runoff at given moment, the input variables are the rainfall and the runoff values observed on the previous time period. Our methodology adopts a real coded GA strategy and hybrid with a back-propagation (BP) algorithm. The genetic operators are carefully designed to optimize the neural network, avoiding premature convergence and permutation problems. To evaluate the performance of the genetic algorithm-based neural network, BP neural network is also involved for a comparison purpose. The results showed that the GA-based neural network model gives superior predictions. The well-trained neural network can be used as a useful tool for runoff forecasting. [Copyright &y& Elsevier]

In this paper, the identification of the hydraulic conductivities in a seawater intrusion problem is investigated. The system of two coupled quasilinear partial differential equations describing the direct problem are solved on the basis of an established maximum principle using a fixed point theorem. The existence of an optimal control is proved, even if the conductivities are discontinuous functions, and the necessary conditions for optimality are obtained. Finally, some numerical results are presented for the sake of illustration. [ABSTRACT FROM AUTHOR]

In the solution of Poisson's equation using either the dual reciprocity boundary element method or the method of fundamental solution, radial basis functions (RBFs) are used to approximate the right-hand side of the governing partial differential equation to eliminate the domain integration. This paper shows that if the RBF interpolation is collocated on the Gaussian quadrature nodes, we seem to observe superconvergence behaviour. This behaviour is demonstrated using a series of numerical examples. Copyright © 2001 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The aim of this paper is to accurately solve short wave scattering problems governed by the Helmholtz equation using the Bernstein–Bézier Finite Element method (BBFEM), combined with a conformal perfectly matched layer (PML). Enhanced PMLs, where curved geometries are represented by means of the blending map method of Gordon and Hall, are numerically investigated. In particular, the performance of radial and elliptical shaped PMLs, with a parabolic absorption function, are assessed and compared in terms of accuracy against second order Bayliss–Gunzberger–Turkel (BGT 2) based local absorbing boundary conditions. Numerical results dealing with problems of Hankel source radiation and wave scattering by a rigid cylinder show that the radial shaped PML, with the h and p versions of BBFEM, enables the recovery of the predicted algebraic and exponential convergence rates of a high order finite element method (FEM). Furthermore, radial shaped BGT 2 and PML have a similar performance, as long as the wave is not sufficiently well resolved. But, BGT 2 performs poorly as the wave resolution increases. Additionally, the effect of harmonics of higher modes on accuracy is examined. The study reveals that the PML outperforms BGT 2 for almost all propagating modes. However, a similar performance is achieved with both methods either with higher modes or a low wave resolution. Results from a multiple scattering benchmark problem provide evidence of the good performance of the proposed PMLs and the benefit of elliptical shaped PMLs in reducing significantly the size of the computational domain, without altering accuracy. The choice of the PML parameters ensuring optimal performance is also discussed. [ABSTRACT FROM AUTHOR]

In this paper, an artificial neural network (ANN) based on hybrid algorithm combining particle swarm optimization (PSO) with back-propagation (BP) is proposed to forecast the daily streamflows in a catchment located in a semi-arid region in Morocco. The PSO algorithm has a rapid convergence during the initial stages of a global search, while the BP algorithm can achieve faster convergent speed around the global optimum. By combining the PSO with the BP, the hybrid algorithm referred to as BP-PSO algorithm is presented in this paper. To evaluate the performance of the hybrid algorithm, BP neural network is also involved for a comparison purposes. The results show that the neural network model evolved by PSO-BP algorithm has a good predictions and better convergence performances [ABSTRACT FROM PUBLISHER]

Eutrophication in water supply reservoirs is a complex phenomenon involving many physico-chemical processes and, therefore, many parameters. Aeration has been confirmed as the best remedial and/or preventive action to minimize or totally eliminate its effects. However, a good understanding of the so-generated flow requires a modelling based on two-phase flow (water–air bubbles) leading to many difficulties. In a previous paper, a first simplified model was suggested; herein, we describe an alternative model taking into account the aeration effect through lumped two-phase flow correction. Numerical experiments are then performed and compared to the previously developed simulator. [ABSTRACT FROM AUTHOR]

In this paper, the eutrophication process in reservoirs is briefly presented, then one of the best remedial actions against it, i.e. aeration, is developed. Multiphase flows are then described to show the complexity of the process and related modeling issues. A first order approximation is then suggested through one-phase flow analysis based on the conventional Navier-Stokes equations to simulate virtually aeration effects in natural reservoirs or lakes by prescribing appropriate internal conditions for velocity to simulate air injection. Though the flow features three-dimensional aspects with variable density, only two-dimensional incompressible fluid flow configurations are considered in this paper to demonstrate the feasibility of the methodology developed. Numerical experiments are then run for scenario analysis. Though the results are somewhat qualitative, they are encouraging and with some kind of validation and calibration a cheap alternative can be offered for studying the aeration process. [ABSTRACT FROM AUTHOR]

Identifies the ground water contaminant source and transport parameter using correlation coefficient optimization. Delineation of the sampled contaminant plume; Projection of the plume history; Occurrence of explicit inverse formulas; Scenarios of ground water pollution; Method of correlation coefficient optimization.

2D shallow water equations with depth-averaged k−ε model is considered. A meshless method based on multiquadric radial basis functions is described. This methods is based on the collocation formulation and does not require the generation of a grid and any integral evaluation. The application of this method to a flow in horizontal channel, taken as an experimental device, is presented. The results of computations are compared with experimental data and are found to be satisfactory [ABSTRACT FROM PUBLISHER]

• A new hydrological regions delineation method based on changepoint analysis is proposed. • Similarity between regions is based on the location of changepoints in time series. • The method allows the estimation of local and regional changing linear trends. • The method was applied to 11 precipitation series in the Tensift basin, Morocco. • Cross-wavelet analysis is used to confirm the homogeneity of the delineated regions. Hydrologic regionalization consists of regrouping stations and catchments in pools based on a similarity measure. Regionalization is commonly used to extract a robust signal that can be used to describe the hydrology of the region or extrapolated to a location without measured information. Obviously, the similarity measure used affects the type of hydrological behavior one would expect from stations within a region. Most regionalization methods assume a stable and/or linear relationship between parameters of interests while it is well known that the physical processes driving the behavior of hydrometeorological variables are inherently non-linear and non-stationary. In this paper, we propose a similarity measure that is based on the location of changepoints in hydrological time series. The proposed method has the unique advantage over other hydrological region delineation methods to detect regions where hydrological member stations are non-linearly correlated, and where the strength of the relation varies with time. It therefore has the potential to uncover similarities that would not have been detected by existing regionalization techniques. The proposed method is applied to the Tensift watershed located in Morocco, North Africa. The coherence of the detected regions is checked using wavelet coherence. [ABSTRACT FROM AUTHOR]

A computer model for assessing the reliability of water-distribution networks is presented. Both mechanical failure caused by pipe breakages and hydraulic failure caused by insufficient pipe capacity are incorporated into a simple stochastic model. A network solver identifies nodal pressures for individual pipe-failure conditions over a range of network demands, where both pipe failure and network demand are of known probabilities. The probabilities of pressure deficiency at nodes are calculated, from which the availability of supply is determined. Two examples are presented to clarify the principles of the model and to demonstrate the practicality of its applications. The model was developed to enable rapid yet realistic analysis of the reliability of water-distribution networks, and can be used for analyzing either existing systems or proposed designs of new systems. [ABSTRACT FROM AUTHOR]