A method is proposed for the treatment of irregular bathymetry in one-dimensional finite volume computations of open-channel flow. The strategy adopted is based on a reformulation of the Saint-Venant equations. In contrast with the usual treatment of topography effects as source terms, the method accounts for slope and nonprismaticity by modifying the momentum flux. This makes it possible to precisely balance the hydrostatic pressure contributions associated with variations in valley geometry. The characteristic method is applied to the revised equations, yielding topographic corrections to the numerical fluxes of an upwind scheme. Further adaptations endow the scheme with an ability to capture transcritical sections and wetting fronts in channels of abrupt topography. To test the approach, the scheme is first applied to idealized benchmark problems. The method is then used to route a severe flood through a complex river system: the Tanshui in Northern Taiwan. Computational results compare favorably with gauge records. Discrepancies in water stage represent no more than a fraction of the magnitude of typical bathymetry variations. 相似文献
We herein propose a simulation-optimization model for groundwater remediation, using PAT (pump and treat), by coupling artificial neural network (ANN) with the grey wolf optimizer (GWO). The input and output datasets to train and validate the ANN model are generated by repetitively simulating the groundwater flow and solute transport processes using the analytic element method (AEM) and random walk particle tracking (RWPT). The input dataset is the different realization of the pumping strategy and output dataset are hydraulic head and contaminant concentration at predefined locations. The ANN model is used to approximate the flow and transport processes of two unconfined aquifer case studies. The performance evaluation of the ANN model showed that the value of mean squared error (MSE) is close to zero and the value of the correlation coefficient (R) is close to 0.99. These results certainly depict high accuracy of the ANN model in approximating the AEM-RWPT model. Further, the ANN model is coupled with the GWO and it is used for remediation design using PAT. A comparison of the results of the ANN-GWO model with solutions of ANN-PSO (ANN-Particle Swarm Optimization) and ANN-DE (ANN-Differential Evolution) models illustrates the better stability and convergence behaviour of the proposed methodology for groundwater remediation.
The objective of the present study was to design, fabricate and evaluate the performance of a novel airi-nducing impeller system with a specially designed air-inducing tube-set. The novel air-inducing impeller system, when attached to a conventional baffled agitated vessel, could convert it into an air-inducing reactor. Water was used as the working fluid and the characteristics of the impeller system such as critical speed, power consumption and gas holdup were investigated by varying the gas free liquid level, orifice immersion depth, bottom clearance and impeller speed. Results showed that this novel air-inducing impeller system induced the air at speeds lower than the critical speeds reported by most of the investigators in the literature. 相似文献
To withdraw large quantities of groundwater from the alluvial aquifers for various uses near riverbeds, radial collector (RC) wells are often preferable to the installation of several small diameter tube wells. In regions where rivers are not perennial or have low flow conditions during most part of the year, the RC wells are placed in the riverbed to obtain uninterrupted supply of naturally filtered groundwater through highly permeable saturated riverbed aquifers. Due to the complexities of flow, no exact analytical solution exists to provide steady state discharge drawdown relationship for RC well. Numerical model construction using finite difference or finite element method is quite cumbersome because of the radial orientation of laterals. To overcome these difficulties, in this study a steady state simulation model based on analytic element method (AEM) is developed to simulate the discharge-drawdown relation for RC well in an unconfined riverbed aquifer. In the model, line-sink elements are used to represent stream as well as radial laterals with specified conductance. The model is used to study the effects of different lateral configurations, hydraulic conductivity of riverbed aquifer, radius of influence and conductance of laterals on the well discharge, and consequent drawdown. Further based on the results of simulations using the AEM model, an approximate empirical equation is developed to obtain the discharge of RC well readily for design purpose. Further, the developed model has been applied to a field study and results are obtained for different plausible configurations of radial wells. The proposed methodology based on the application of AEM modeling tool, has been found to be efficient in constructing riverbed aquifer model with RC well. The proposed model is recommended in designing new collector well by providing minimum length of laterals for the sustained yield. 相似文献
Water treatment process involving simultaneous action of adsorption on different nano and organo-modified nano-clays followed by coagulation-flocculation by alum and poly aluminium chloride (PAC) has been evaluated for the removal of PAHs (naphthalene, acenaphthalene, phenanthrene, fluoranthene, anthracene, and pyrene) from water. When clay minerals along with alum and PAC were used for treatment, 37.4–100.0% removal of PAHs was observed compared to 20–38% removal using normal water treatment process with either alum or alum + PAC. The effectiveness of clay minerals for removal of PAHs followed the order (P < 0.05): halloysitenano-clay (HN-clay) < normal bentonite (NB-clay) < hydrophilic nano-bentonite (HNB-clay) < nano-montmorillonite modified with dimethyl dialkyl amine (DMDA-M-clay) ≈ nano-montmorillonite modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M-clay) ≈ nano-montmorillonite modified with octadecylamine (ODA-M-clay) in combination with alum + PAC. The modified treatment process (alum + PAC + clay minerals), where water was initially treated with clays followed by normal process of coagulation (alum + PAC), was found to be the most effective method with maximum removal for ODAAPS-M-clay (97.7–100.0%) which is at par wih ODA-M (97.0–100.0%), and DMDA-M-clay (94.8–100%). The removal of PAHs varied in the order: naphthalene ≈ acenaphthalene > anthracene ≈ pyrene > phenanthrene > fluoranthrene. The treatment combination having the maximum removal capacity was also used eficiently for the removal of PAHs from natural and fortified natural water. This article demonstrated adsorption-coagulation integrated system has the potential to remediate PAHs polluted water. 相似文献
A meshless simulation model based on the radial point collocation method (RPCM) is developed in this study to simulate contaminant transport in heterogeneous aquifers with nonlinear adsorption. The nonlinear adsorption is represented using popularly used Langmuir’s isotherm. The nonlinear governing equation of the contaminant transport is solved utilizing linearization through timesteps. The directional derivatives of hydraulic conductivity field through vectorization are used to simulate flow in highly heterogeneous aquifers. Multiquadrics radial basis functions (MQ-RBF) are used for the approximation of heads and concentrations and their gradients. The relevant equations are solved locally using the domain decomposition technique, which avoids the ill-conditioning issue associated with globally supported domains. The developed models are named RPCM-NA (for only transport) and RPCM-CNA (for coupled flow and transport). The RPCM-NA model is validated against semi-analytical solutions, and its advantages over the Finite Difference Method (FDM) are demonstrated. Two case studies are considered. The performance of the RPCM-CNA model is compared to that of FDM-based MODFLOW and MT3DMS models, with the maximum percentage error for head estimation being 0.25%. For contaminant transport simulation in the mobile and adsorbed phases, the maximum values of Normalized Mean Absolute Error obtained are 0.02 and 0.0385 respectively, showing the effectiveness of the proposed model.
A number of models with conventional optimization techniques have been developed for optimization of reservoir water release
policies. However these models are not able to consider the heterogeneity in the command area of the reservoir appropriately,
due to non linear nature of the processes involved. The optimization model based on genetic algorithm (GA) can deal with the
non linearity due to its inherent ability to consider complex simulation model as evaluation function for optimization. GA
based models available in literature generally minimize the water deficits and do not optimize the total net benefits through
optimal reservoir release policies. The present study focuses on optimum releases from the reservoir considering heterogeneity
of the command area and responses of the command area to the releases instead of minimizing only the reservoir storage volumes.
An optimization model has been developed for the reservoir releases based on elitist GA approach considering the heterogeneity
of the command area. The developed model was applied to Waghad irrigation project in upper Godavari basin of Maharashtra,
India. The results showed that 19% increase in the total net benefits could be possible by adopting the proposed water release
policy over the present practice keeping same distribution of area under different crops. The model presented in this study
can also optimize the crop area under irrigation. It is found that irrigated area can be increased to 50% of ICA (Irrigable
Command Area) from the existing 23% with resulting addition to total net benefits by 31%. The effect of adopting the proposed
irrigation schedule and increased irrigation areas would be to increase the net benefits to existing farmers. 相似文献