Department of Civil & Infrastructure Engineering

&ldquo;IIT Jodhpur is committed to impart quality education to facilitate the creation of qualified, competent and responsible human resources to meet the emerging technological challenges of the world. It is working towards creating an equitable learning platform that is positive, accessible and effective in the face of the modern societal and scientific advancements.

Flexibility in curriculum, in all its academic programs, encompassing elements of teaching, research, creativity, innovation and entrepreneurship is the most unique feature of IIT Jodhpur. The Department of Science and Technology (DST), under the National Mission on Cyber Physical Systems, has identified IIT Jodhpur as a Technology &amp; Innovation Hub in the area of Augmented Reality and Virtual Reality. The institute has also been nominated as the coordinator for the Jodhpur City and Knowledge Cluster by the Office of Principal Scientific Adviser, Government of India.

The sprawling 852-acre IIT Jodhpur campus is a majestic tribute to the deep-rooted diverse cultural heritage of the region. The campus is an architectural masterpiece, which is slated to become an international exemplar of sustainability with net-zero energy, and advanced water and waste management strategies.&rdquo;

IIT Jodhpur

Vegetation present in the water streams, on the banks and in the floodplain areas largely affects the river hydraulics. Indeed, river vegetation significantly influences hydrodynamics, sediment transport, bedforms, and pollutant transport. Environmental management of rivers requires an understanding of the various processes and predictive capabilities of models. In the past, many studies were conducted, especially in laboratory settings, in order to quantify flow resistance due to vegetation. It is only recently that the effects of vegetation on sediment transport came to the attention of researchers. In particular, both suspended and bedload transport were considered. This paper reviews recent works conducted on the effect of vegetation on incipient sediment motion and bedload transport. With regard to the incipient sediment motion, methods based on critical velocity, turbulence, vegetation drag, and velocity in the bed roughness boundary layer have been discussed. For bedload transport, methods based on bed shear stress, turbulent kinetic energy, a revisiting of classical formulas for estimating bedload transport in non-vegetated channels, and estimation from erosion around a single vegetation stem are analyzed. Finally, indications on further research and new development are provided. © 2023, The Author(s).

World University root node

Fulltext

Environmental Fluid Mechanics

Bedload transport through emergent vegetation: current status and its future prospect

Effective treatment of water contaminated with hexavalent chromium is vital due to its genotoxic and carcinogenic nature. Considering the new stringent regulatory limits being set up for Cr(VI) in ground and surface water, it is imperative to develop efficient treatment technologies/materials for the remediation of Cr(VI)-laden impaired waters. The most common issue is the lack of selectivity of sorbents towards chromate anion and their performance in real systems. Of late, polyethylenimine (PEI) polymer-based adsorbents have gained escalating attention of researchers, owing to their redox properties and biocompatible nature. Here we review various PEI-based adsorbents developed so far to remove Cr(VI) from contaminated waters. Based on the relevant peer-reviewed articles available in the open literature, the adsorbents can be divided into six broad categories, depending on the substrate used for PEI immobilization: magnetic materials, carbon-based, silica-based, clay minerals and geomaterials, biologically-derived materials, and other hybrid composites. This review discusses the efficiency of various PEI-based adsorbents for Cr(VI) removal; facilitates a better understanding of the removal mechanism and the regeneration process of the spent adsorbents. A critical evaluation of the existing literature, research shortcomings, and future research directions required to devise improved methodologies for practical applications have also been provided. Researchers who desire to work on Cr(VI) removal, with an inclination towards developing sophisticated adsorbents, can benefit from this article. © 2023 Elsevier Ltd

Journal of Environmental Chemical Engineering

Removal of hexavalent chromium from impaired water: Polyethylenimine-based sorbents − A review

This study presents an analytical model of a steady turbulent flow over a two-dimensional downstream-skewed wavy bed of small amplitude. The mathematical framework rests on the time-averaged continuity and Reynolds-averaged Navier-Stokes (RANS) equations. The streamwise velocity profile is considered to follow a self-similar power law, whereas the Reynolds normal stresses are founded on the turbulent diffusivity hypothesis. The curvilinearity in flow streamlines induced by the wavy bed is introduced into the analysis via Boussinesq approximation. The analysis provides solutions to the free-surface, bed shear stress, and Reynolds shear stress profiles. As the flow Froude number varies, the free-surface and bed shear stress profiles change their phases. The phase shift of the free-surface profile with respect to the bed profile decreases with an increase in skewness factor, whereas the phase shift of the bed shear stress profile with respect to the bed profile increases with an increase in skewness factor attaining a constant value. The convex and concave shapes of the Reynolds shear stress profiles on the downslope and upslope of the bed profile are attributed to the decelerated and accelerated flows, respectively. The implementation of the key findings of this work to study the hydrodynamics of fluvial bedforms is discussed from the standpoint of sediment transport, as a future scope of research. © 2023 American Society of Civil Engineers.

Journal of Hydraulic Engineering

Turbulent Shear Flow over a Downstream-Skewed Wavy Bed: Analytical Model Based on the RANS Equations with Boussinesq Approximation

Geogrids embedded in fill materials are checked against pullout failure through standard pullout testing methodology. The test determines the pullout interaction coefficient which is critical in fixing the embedment length of geogrids in mechanically stabilized earth walls. This paper proposes prediction of pullout interaction coefficient using data driven machine learning regression algorithms. The study primarily focusses on using extreme gradient boosting (XGBoost) method for prediction. A data set containing 220 test results from the literature has been used for training and testing. Predicted results of XGBoost have been compared with the results of random forest (RF) ensemble learning based algorithm. The predictions of XGBoost model indicates 85% accuracy and that of RF model shows 77% accuracy, indicating significantly superior and robust prediction through XGBoost above RF model. The importance analysis indicates that normal stress is the most significant factor that influences the pullout interaction coefficients. Subsequently pullout tests have been performed on geogrid embedded in four different fill materials at three normal stresses. The proposed XGBoost model gives 90% accuracy in prediction of pullout interaction coefficient compared to laboratory test results. Finally, an open-source graphical user interface based on the XGBoost model has been created for preliminary estimation of the pullout interaction coefficient of geogrid at different test conditions.

Geotextiles and Geomembranes

Prediction of pullout interaction coefficient of geogrids by extreme gradient boosting model

Prolonged exposure to trace Cr(VI) concentrations in potable water can cause serious health problems in living beings. A weak base anion exchange resin, Duolite A7, showed a large capacity for trace Cr(VI) removal from a background of competing anions present at much higher concentrations, while conventional ion exchangers and adsorbents become ineffective due to lack of selectivity under similar conditions. The objective of this study was to find out the mechanism behind such significant capacity shown by the resin. Fixed-bed column studies showed that the resin was fully exhausted below 4,000 bed volumes (BVs) for pH 7, whereas no breakthrough was observed for 25,000 and 131,000 BVs at pH 5 and 3, respectively. Extensive characterization studies revealed that redox reactions were also occurring inside the resin in addition to ion exchange, where Cr(VI) oxidized the amine functional groups and phenol–formaldehyde matrix while itself getting reduced to Cr(III). Cr(III) formed was either precipitated inside the resin as Cr(OH)3 or bound with the oxidation products such as carboxylic acid groups. Analysis of treated water showed that formaldehyde, a carcinogen, was formed due to oxidative attack of Cr(VI) on the resin and was released in the effluent at trace concentrations. A detailed understanding of the mechanism would motivate the development of such redox-active sorbents for selective trace Cr(VI) removal from contaminated drinking water. © 2022 The Korean Society of Industrial and Engineering Chemistry

Journal of Industrial and Engineering Chemistry

Detailed investigation of effective trace Cr(VI) removal mechanism by anion exchange resin with phenol–formaldehyde matrix

We study the dynamics of an erodible sinuous channel subject to combined curvature and autogenic width oscillations. We find that generic grain transport (both bedload and suspended load transport) amplifies lateral stretching of the channel centerline and enhances the maximum width-variation amplitude and curvature ratio in their temporal dynamics by displaying a phase lag. However, in the initial and mature stages, the planform dynamics asymptotically approaches the conventional limits. The planform evolution is found to be influenced by four key parameters: Shields number, relative roughness, channel aspect ratio, and shear Reynolds number. The findings of this study, to the best of our knowledge, represent the first analytical investigation of the planform evolution of a sinuous channel driven by generic grain transport. © 2022 Author(s).

Physics of Fluids

Planform evolution of a sinuous channel triggered by curvature and autogenic width oscillations due to generic grain transport

Even though both fluid mechanics and numerical studies have considerably progressed in the past decades, experimental knowledge remains an important tool for studying the resistance to flow in fluid media where a complex environment dominates the flow pattern. After a comprehensive review of the recent literature on the drag coefficient in open channels with emergent rigid vegetation, this paper presents the results related to 29 experimental accelerated subcritical flow profiles (i.e., M2 type) that were observed in flume experiments with emergent stems in a square arrangement at the University of Calabria (Italy). First of all, we used some of the literature formulas for the drag coefficient, concluding that they were unsatisfactory, probably because of their derivation for uniform or quasi-uniform flow conditions. Then, we tested a recently proposed approach, but when we plotted the drag coefficient versus the stem Reynolds number, the calculated drag coefficients showed an inconclusive behavior to interpret. Thus, we proposed a new approach that considers the calibration of the Manning coefficient for the simulation of the free surface profile, and then the evaluation of the drag coefficients based on the fundamental fluid mechanics equations. With the help of classical dimensional analysis, a regression equation was found to estimate the drag coefficients by means of non-dimensional parameters, which include vegetation density, stem Reynolds number and flow Reynolds number computed using the flow depth as characteristic length. This equation was used to simulate all the 26 observed profiles and, also, 4 experimental literature profiles, and the results were good. The regression equation could be used to estimate the drag coefficient for the M2 profiles in channels with squared stem arrangements, within the range of vegetation densities, flow Reynolds numbers and stem Reynolds numbers of the present study. However, in the case of the three profiles observed by the authors for staggered arrangement, the regression equation gives significantly underestimated flow depths. © 2022 by the authors.

Applied Sciences (Switzerland)

Simulation of Accelerated Subcritical Flow Profiles in an Open Channel with Emergent Rigid Vegetation

Abstract In this study, we present a three-dimensional numerical model for the interaction of flow with submerged flexible vegetation, based on a large-eddy simulation and the immersed boundary method. The model innovatively realises the interaction between the flow and highly flexible vegetation with clustered leaves. Besides being a three-dimensional model of motion with full degrees of freedom, this study improves the consideration of the motion of the vegetation in all directions, and in addition the energy and momentum transfer in the spanwise direction. Furthermore, we perform a flume experiment for the flow with submerged flexible vegetation, the results of which are used to validate the simulation effects of the numerical model. It is found that the numerical model can effectively simulate the velocity profiles and the movement of vegetation induced by the flow. Using the model to analyse the flow-vegetation interaction, we find that the movement of vegetation is closely related to the flow velocity. As the flow velocity increases, both the offset angle and the vegetation swaying amplitude increase. Compared to vertical rigid vegetation, the tilting of flexible vegetation does not significantly change the velocity difference and the magnitude of the turbulent kinetic energy between the inside and the outside of the vegetation canopy, but it does weaken the disturbance to flow, thus reducing the resistance to flow. However, the swaying of vegetation dose significantly increase the velocity difference between the inside and the outside of the canopy. It forms Kelvin-Helmholtz hairpin vortices intensifying the turbulence production, and enhancing the disturbance and resistance to flow. ©

Journal of Fluid Mechanics

Influence of submerged flexible vegetation on turbulence in an open-channel flow

With increasing groundwater and surface water contamination due to improper discharge of chromium-laden wastewaters, it is compelling to synthesize a material that can selectively remove Cr(VI) from the impaired water at neutral or near-neutral pH. In this study, various composites were synthesized through chemical grafting of polyethylenimine (PEI) polymer on the surface of INDION PA 800 polystyrene beads by varying the PEI loading and glutaraldehyde (GA) crosslinking for Cr(VI) removal. The adsorbent called PS-7 with 16% PEI and 2.5% GA crosslinking performed best, demonstrating Cr(VI) removal greater than 99% even at pH 9. The adsorbent showed significant trace Cr(VI) removal from the impaired solution containing competing anions at 500 times the concentration of Cr(VI) at neutral pH. Further, 1.0 g/L adsorbent showed 100% Cr(VI) removal from a solution containing 5 mg/L Cr(VI) at pH 7 and 9. PS-7 showed significant adsorption capacity of 355.26 and 143.6 mg/g for fixed-bed column runs at influent pH 3 and 5, respectively. An insightful investigation revealed that the use of hydrophobic matrix for PEI immobilization played an important role in Cr(VI) removal at neutral pH, as opposed to the other reported PEI-based adsorbents with hydrophilic matrix which were capable of removing chromate anions at acidic pH only. The phenomenon of redox reaction occurring in the adsorbent was validated by X-ray photoelectron spectroscopy, where Cr(VI) was reduced to Cr(III) with the help of electron-donating NH2 groups and the adsorbent got oxidized. Thus, PS-7 adsorbent holds immense potential for treating real-life Cr(VI)-contaminated waters. © 2022 Elsevier Ltd

Synthesis and validation of polystyrene-based polyethylenimine composite for Cr(VI) removal from aqueous solution: Performance and mechanism

The flow over uneven topography is a problem of interest in environmental fluid flow modeling, including flows over river bedforms, exchange flows over oceanic sills or the airflow over mountains. The common experimental procedure to investigate these flows, moving a small obstacle in a laboratory flume, yields experimental difficulties, whereas modeling using non-linear shallow flow equations does not explain all the flow phenomena. Novel alternative procedures are presented for the experimentation and shallow water representation of flow interaction with obstacles. A large-scale obstacle model is constructed in a dam-break set-up, and used to generate flow phenomena over topography, including dispersive and broken surges, wave reflection, hydraulic jumps and non-hydrostatic sill overflows. Simulations are conducted with a shallow-water weighted-averaged residual flow software for turbulent flows. The proposed software reproduces the experiments satisfactorily, supporting its use in modeling, whereas the new experimental database can be used by modelers to test their software. © 2022 Elsevier Ltd

Environmental Modelling and Software

Shallow-water lee-side waves at obstacles: Experimental characterization and turbulent non-hydrostatic modeling using weighted-averaged residual equations