Hydrodynamics and Salinity Transport Modeling in Branched Estuary Channels Using Finite Element Method

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Analytic Element Method and Genetic Algorithm Based Models For Estimating Stream Bed Resistance

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Inverse Modeling Of Groundwater System Using Coupled PSO-MLPG Techniques

The effective management of groundwater systems relies on the adequate knowledge of its hydro-geological parameters. In large aquifer systems, it is often computationally expensive to estimate the spatially distributed aquifer parameters. Inverse modeling of these parameters are usually required in simulation of flow and contaminant transport in the problem domain for its meaningful system prediction. In the present study, a new approach for inverse modeling is adopted based on Meshless Local Petrov Galerkin (MLPG) flow simulation model which is coupled with Particle Swarm Optimization (PSO) model. MLPG is one of the meshless techniques, which are recently developed to solve many partial differential governing equations in various engineering fields. Here, without using a pre-defined mesh, the system of equations are established for the entire domain. In MLPG, only appropriate distribution of nodes is utilized in the modeling. The nodes are used for approximation of the governing equations by using support domain. This alleviates the huge efforts required in pre-processing for groundwater modeling, as in mesh based methods. The numerical model is developed in 2 dimensions using MATLAB. The standard PSO algorithm is used for optimization and both simulation optimization models are coupled. The model is applied to a hypothetical confined aquifer to compute transmissivity in different zones of the aquifer. The stability of the estimated parameter is investigated by considering different sets of head data, assuming error free head and different sets involving measurement errors. The solutions are compared with other inverse models using the Levenberg-Marquardt Algorithm (LMA) and Genetic Algorithm (GA). The PSO results are comparable with LMA and are better compared to GA estimates. From the results we can say that the model can be applied to obtain optimal estimates of the aquifer parameters in the regional groundwater systems

Inconsistent Atmosphere‐Ocean Dynamics and Multidecadal Zonal SST Gradient Trends Across the Equatorial Pacific Ocean in Reanalysis Products

Ocean reanalysis products are routinely employed as reality checks in model evaluations and for process studies. This is especially so for critical regions such as the equatorial cold tongue (ECT) in the eastern equatorial Pacific where models suffer a chronic cold bias. ECT is a major player in the Pacific equatorial zonal sea surface temperature (SST) gradient (ΔEWSST) that has a significant impact on oceanic heat uptake and thus global climate. Hence, we investigate the reliability of three ocean reanalysis products for surface flux and ocean dynamic controls on ΔEWSST and Niño3.4 SST trends. We infer that while Niño3.4 SST trends are positive in all products, the signs of ΔEWSST trends do not agree with each other because initial conditions likely play a big role in their evolution. However, for ΔEWSST trends, the effect of initial conditions gets canceled out to some extent. Mixed layer heat budget and trends in ocean dynamic features such as tropical and subtropical cells, equatorial undercurrent, and subsurface temperatures are also diagnosed. We show that two reanalysis products that show a strengthening of ΔEWSST have contradicting trends in their surface heat flux and ocean dynamic contributions. This suggests that without accurate surface heat and momentum fluxes, data assimilation techniques may produce an east–west trend that is inconsistent among each other. Reanalysis products must address these issues considering the importance of this gradient

A Comprehensive Study of Assessing Sustainable Agricultural Water Management under Changing Climate Scenarios—A Regional Basis Study in the Western Ghats, India

The Western Ghats (WG) in South India is a biological hotspot with a cluster of small river basins and heterogeneous climate and vegetation patterns, and it is categorized under the water stress region by Central Water Commission (CWC). This study aims to evaluate the effects of climate change and land use/land cover (LULC) transformations on water balance components and irrigation water demand (IWD) across different regions of WG for a future period (2020–2050). The variable infiltration capacity model has been calibrated separately for the upper, middle, and lower regions of WG. Further, climate projections from the CMIP6 experiment (SSP2 45/SSP5 85) have been used for future projections of water balance components. The land use change shows an increase in built-up (5.79%) and a decrease in cultivable land (1.24%) by the end of 2030 from 1995. The combined impact due to climate and LULC change shows that the future rainfall/runoff increases in the lower regions of the basin by 100/36.5 mm/year through SSP 4.5. However, the summer months show an increasing water requirement in the future for the Ghats and Nilgiri regions of the basin. The present regional-based study will be useful for future agriculture water management practices in the region for sustainable development and the study can be extended to other similar regions

Evaluating the effect of aquifer heterogeneity on multiobjective optimization of in-situ groundwater bioremediation

In-situ bioremediation is a cost-effective technique to eliminate petroleum hydrocarbons from groundwater. In previous studies, this has been mostly applied under the approximation of a homogeneous porous medium, even though in reality aquifers are often characterized by significant heterogeneities. Here, different heterogeneous and equivalent homogeneous hydraulic conductivity fields are considered to study the effect of aquifer heterogeneity on optimal in-situ bioremediation. For this, the multiobjective simulation-optimization (S/O) model referred to as BIOEFGM-NSGA II is proposed — which uses the element-free Galerkin method (EFGM) for discretization of the governing equations, and the non-dominated sorting genetic algorithm II (NSGA II) for multiobjective optimization. This model is then applied to different heterogeneous conductivity fields generated through a pseudo-random correlated field generator for different combinations of variance and correlation lengths with constant mean. Results show that the optimal pumping policy for an equivalent homogeneous conductivity field violates the constraint of maximum allowable concentration in all the studied heterogeneous fields. To satisfy this constraint, in-situ bioremediation cost increases by 8.47% to 56.83% to that of a homogeneous field. It shows the significance of aquifer heterogeneity in designing an optimized in-situ bioremediation system and hence, should be incorporated in the S/O model for in-situ groundwater bioremediation

Performance Study of Modified Savonius Water Turbine with Two Deflector Plates

Savonius rotor is a vertical axis rotor with simple in design and easy to fabricate at lower cost. The rotation of the rotor is due to the drag difference between the advancing blade and returning blade. Net driving force can be increased by reducing the reverse force on the returning blade or increasing the positive force on the advancing blade. Former can be realized by providing a flow obstacle to the returning blade and latter can be realized by concentrating the flow towards the advancing blade. The objective of the present work is to identify the optimal position of the deflector plate (on advancing blade side) placed upstream to the flow which would result in increase in power generated by the rotor. Tests are conducted to identify the optimum position of the deflector plate on the advancing blade side in the presence of a deflector plate on the returning blade side at its optimum position. Results suggest that two deflector plates placed at their optimal positions upstream to the flow increase the coefficient of power to 0.35. This is significantly higher than the coefficient of power of 0.14 observed for the rotor without deflector plates

Study on the Interaction between Two Hydrokinetic Savonius Turbines

Savonius turbine is simple in design and easy to fabricate at a lower cost. The drag is the basic driving force for Savonius turbine. Savonius turbines are mainly used for the small-scale electricity generation in remote areas. In real life, multiple Savonius turbines are to be arranged to form a farm to scale up the electricity generation. So, it is important to study the interaction among them to avoid the power loss due to negative interaction between turbines. The purpose of this investigation is to examine closely the effect of interaction between two Savonius turbines arranged in line. Experimental investigations are carried out to study the mutual interaction between turbines with water as the working medium at a Reynolds number of 1.2×105 based on the diameter of the turbine. Influence of separation gap between the two Savonius turbines is studied by varying the separation gap ratio (/) from 3 to 8. As the separation gap ratio increases from 3 to 8, becomes lesser the mutual interaction between the turbines. Results conclude that two turbines placed at a separation gap ratio of 8 performed independently without affecting the performance of each other