Browsing by Author "Munusamy, Selva Balaji"

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Analytical solution of groundwater waves in unconfined aquifers with sloping boundary
(Springer, 2017-07) Munusamy, Selva Balaji
A new analytical solution is derived for tide-driven groundwater waves in coastal aquifers using higher-order Boussinesq equation. The homotopy perturbation solution is derived using a virtual perturbation approach without any pre-defined physical parameters. The secular term removal is performed using a combination of parameter expansion and auxiliary term. This approach is unique compared with existing perturbation solutions. The present first-order solution compares well with the previous analytical solutions and a 2D FEFLOW solution for a steep beach slope. This is due to the fact that the higher-order Boussinesq equation captures the streamlines better than ordinary Boussinesq equation based on Dupuit’s assumption. The slope of the beach emerges as an implicit physical parameter from the solution process.
Appraising the Accuracy of Multi-Class Frequency Ratio and Weights of Evidence Method for Delineation of Regional Groundwater Potential Zones in Canal Command System
(Springer, 2017-06) Munusamy, Selva Balaji
A comparative study of probabilistic frequency ratio (FR) and weights of evidence (WofE) method is performed for delineation of regional groundwater potential zones (GPZ) in canal command system. In the present case study, delineation of GPZ in the Hirakud agricultural command area of Odisha, India. Field discharge data from borewells are utilized for the analysis along with remote sensing (RS) and geographic information system (GIS) techniques. Various influencing attributes responsible for occurrence and movement of groundwater, e.g., land use / land cover, soil type, groundwater depth, geology, elevation, geomorphology, slope, recharge rate, rainfall, normalized difference vegetation index, drainage density, crop intensity are integrated by using GIS platform. Model results from FR and WofE show similar trends. The middle portion of the study area covers the ‘Good’ GPZ. Sensitivity analyses are performed for FR and WofE methods.
Can We Remove Secular Terms for Analytical Solution of Groundwater Response under Tidal Influence?
(ARXIV, 2016-05) Munusamy, Selva Balaji
This paper presents a secular term removal methodology based on the homotopy perturbation method for analytical solutions of nonlinear problems with periodic boundary condition. The analytical solution for groundwater response to tidal fluctuation in a coastal unconfined aquifer system with the vertical beach is provided as an example. The non-linear one-dimensional Boussinesq's equation is considered as the governing equation for the groundwater flow. An analytical solution is provided for non-dimensional Boussinesq's equation with cosine harmonic boundary condition representing tidal boundary condition. The analytical solution is obtained by using homotopy perturbation method with a virtual embedding parameter. The present approach does not require pre-specified perturbation parameter and also facilitates secular terms elimination in the perturbation solution. The solutions starting from zeroth-order up to third-order are obtained. The non-dimensional expression, A/D∞ emerges as an implicit parameter from the homotopy perturbation solution. The non-dimensional solution is valid for all ranges of A/D values. Higher order solution reveals the characteristics of the tidal groundwater table fluctuations.
Delineation of Groundwater Potential Zones of Coastal Groundwater Basin Using Multi-Criteria Decision Making Technique
(Springer, 2016-07) Munusamy, Selva Balaji
Delineation of groundwater potential zones (GWPZ) has been performed for a coastal groundwater basin of eastern India. The groundwater potential zone index (GWPZI) map is generated by using Analytic Hierarchy Process (AHP) from different influencing features, e.g., Land Use/Land Cover (LU/LC), soil (S), geomorphology (GM), hydrogeology (HG), surface geology (SG), recharge rate (RR), drainage density (DD), rainfall (RF), slope (Sl), surface water bodies (SW), lineament density (LD), and Normalized Difference Vegetative Index (NDVI). Recharge rate values are estimated from hydrological water balance model. Overlay weighted sum method is used to integrate all thematic feature maps to generate GWPZ map of the study area. Four zones have been identified for the coastal groundwater basin [very good: 36.39 % (273.53 km2, good: 43.57 % (327.47 km2), moderate: 18.27 % (137.30 km2), and poor: 1.77 % (13.27 km2)]. Areas in north to south-west and south-east direction show very good GWPZ due to the presence of low drainage density. GWPZ map and well yield values show good agreement. Sensitivity analysis reveals that exclusion/absence of rainfall and lineament density increases the poor groundwater potential zones. Omission of hydrogeology, soils, surface geology, and NDVI show maximum increase in good GWPZ. Obtained GWPZ map can be utilized effectively for planning of sustainable agriculture. This analysis demonstrates the potential applicability of the methodology for a general coastal groundwater basin.
Experimental and numerical investigation of saltwater intrusion dynamics on sloping sandy beach under static seaside boundary condition
(Elsevier, 2020-10) Munusamy, Selva Balaji
Two-dimensional sandbox experiments were conducted to investigate the variable-density circulation and flow patterns in sloping beach configurations. The experiments provide new benchmark results for validating the sandbox models based on quantitative and qualitative measurements. Previous studies have considered density dependent flow in porous media, vertical beach face saltwater boundary, and multilayered hydrogeology ignoring a sloping beach face, which is a much more common phenomenon in real world. The present study considers sloping beach face under both homogeneous and low-permeability strata configurations. The geohydraulic processes encountered were quantified through pore-water pressure measurements and image analysis techniques. Moreover, validations were performed with numerical simulations (FEFLOW). A simple image analysis procedure is proposed with respect to two-dimensional laboratory scale benchmark experiments. Experimental results provided a detailed circulation flow path within and outside the saltwater wedge with sloping beach face. Fingering effect in porous media was also observed for both the experiments during initial time periods. Stability analysis shows the existence of a stationary convective flow pattern followed by gravitational instabilities under the quasi-steady state condition.
Homotopy Perturbation Method-Based Analytical Solution for Tide-Induced Groundwater Fluctuations
(Wiley, 2015-09) Munusamy, Selva Balaji
The groundwater variations in unconfined aquifers are governed by the nonlinear Boussinesq's equation. Analytical solution for groundwater fluctuations in coastal aquifers under tidal forcing can be solved using perturbation methods. However, the perturbation parameters should be properly selected and predefined for traditional perturbation methods. In this study, a new dimensional, higher-order analytical solution for groundwater fluctuations is proposed by using the homotopy perturbation method with a virtual perturbation parameter. Parameter-expansion method is used to remove the secular terms generated during the solution process. The solution does not require any predefined perturbation parameter and valid for higher values of amplitude parameter A/D, where A is the amplitude of the tide and D is the aquifer thickness.
Micro-macro–scale flood modeling in ungauged channels: Rain-on-grid approach for improving prediction accuracy with varied resolution datasets
(Elsevier, 2025-06) Srinivas, Rallapalli; Munusamy, Selva Balaji; Gupta, Rajiv
Flood risk arises from the interplay of climatic variability, urbanization, and mitigation measures. While climatic patterns exhibit variability that may either exacerbate or mitigate flood risk across regions, urban development continues to decrease the distance between human settlements and flood-prone areas, intensifying vulnerability. This also necessitates the utilization of datasets with diverse resolutions. Although several studies have performed flood forecasting using advanced models, challenges remain in addressing specific limitations such as (a) improving the accuracy of micro–macro-scale model transitions when employing varied resolution datasets, and (b) enhancing predictive capabilities for ungauged channels. This study aims to address these challenges within the context of a case study, applying a rain-on-grid approach to link micro- and macro-scale flood predictions in a data-scarce environment. The study investigated the impact of grid size and simulation time steps for daily rainfall data on computation time and model accuracy through Geo-HECRAS. The results highlighted significant impacts on the accuracy of hydrological simulations due to variations in spatial resolution and simulation time steps. Volume accumulation error decreased from 1.49 % to 0.25 % in micro-scale scenarios and from 0.85 % to 0.006 % in macro-scale scenarios when transitioning from higher-resolution grids (5 m and 30 m) to coarser grids (10 m and 50 m) with a finer simulation time step of 15 min. While finer grids improve spatial detail, the findings suggest that coarser grid resolutions, when combined with finer temporal scales, can achieve reduced errors and optimized computational efficiency for both micro and macro-scale modeling. This approach enhances the accurate representation of flood dynamics over broader spatial scales, ensuring the reliability of predictive models. It supports the development of flood mitigation strategies and resilient infrastructure tailored to both regional patterns and site-specific hydrological conditions.
On Use of Expanding Parameters and Auxiliary Term in Homotopy Perturbation Method for Boussinesq Equation with Tidal Condition
(Springer, 2018-10) Munusamy, Selva Balaji
This paper uses the homotopy perturbation method for the analytical solution of groundwater table fluctuations, in response to the tidal boundary condition, for a coastal unconfined aquifer with sloping beach face. The Boussinesq equation for sloping beach contains two non-linear terms. The governing equation is reconstructed in homotopic form with two virtual perturbation parameters and an auxiliary term. The secular terms generated from the non-linear diffusion term and the slope term are eliminated by using parameter expansions based on two virtual parameters. Two non-dimensional parameters emerge from the solution in the process of eliminating secular terms: (i) parameter equivalent to amplitude parameter and (ii) parameter representing beach slope. The second-order (starting from zeroth-order) solution is presented. The higher-order solution efficiently captures the non-linearity of the problem.
Optimal Control of Saltwater Intrusion in Coastal Aquifers Using Analytical Approximation Based on Density Dependent Flow Correction
(Springer, 2020-01) Munusamy, Selva Balaji
Pumping well management in coastal aquifers required to account for the saltwater intrusion problem. The prevention saltwater contamination of pumping wells should be considered along with the objective of maximum groundwater withdrawal. Saltwater intrusion constraint can be based on (1) sharp interface model (2) density-dependent transport model. Sharp interface models are preferable in the case of limited computation cost available and density-dependent transport models are preferable for accuracy. The correction factor introduced to account for the density-dependent dispersion by Pool and Carrera (Water Resour Res 47(5):W05506, 2011) vastly improves the sharp interface solution. In this present study, the application of the modified sharp interface solution based on the density-dependent correction factor for the pumping optimization is demonstrated for a regional scale aquifer in Nellore, Andhra Pradesh, India. The proposed optimization model sought to maximize the total pumping and minimize the landward toe intrusion from the sea.