Department of Civil & Infrastructure Engineering

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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

IIT Delhi

Feasibility of using coal bottom ash, pond ash or fly ash as structural fill material in mechanically stabilized earth walls

Conditional turbulence and dispersion characteristics in flow over a series of two-dimensional dunes are analyzed by applying the spatial averaging methodology. To this end, the flow data measured over an array of points on the vertical central plane were used. The manifestation of the wake-interference flow over dunes, including the boundary layer diffusion, flow separation, and flow reattachment, is demonstrated by overlapping the vorticity contours on the velocity vector diagram. The vertical distributions of the spatially averaged (SA) streamwise velocity, Reynolds shear and normal stresses, dispersive shear and normal stresses, turbulent kinetic energy (TKE) fluxes, and dispersive kinetic energy (DKE) fluxes are analyzed. It is recognized that the dominance of the conditional SA streamwise velocity associated with the temporal sweep events causes the flow to accelerate temporally. The conditional SA Reynolds stresses and TKE fluxes associated with the temporal ejection events are dominant above the dune crest, whereas those associated with the temporal sweep events are the governing mechanism below the crest. An examination of the conditional dispersive normal stresses and the DKE fluxes reveals that within the upper portion of the roughness sublayer, the dispersive ejection events are the key flow dispersion mechanism, whereas near the dune trough, the dispersive outward interaction events prevail. Furthermore, the temporal ejection events are found to be more persistent, but less frequent, than the temporal sweep events. Besides, the frequencies of the occurrences of the temporal bursting events are higher below the crest than those above it, suggesting the flow to be more turbulent below the crest. © 2020 Author(s).

World University root node

Physics of Fluids

Conditional spatially averaged turbulence and dispersion characteristics in flow over two-dimensional dunes

The study deals with the variations of third-order moments of velocity fluctuations, turbulent bursting and turbulent kinetic energy (TKE) budget downstream of an isolated dune mounted on a rough bed in an open channel. The experimental data demonstrates that in the wall-wake flow, the third-order moments change their signs below the crest level of the dune, whereas their signs remain unchanged above the crest. The near-wake flow is characterized by sweep events and the far-wake flow is governed by the ejection. In the near-wake flow, the mean duration of bursting events is shorter than their mean interval of occurrence. Downstream of the dune, the turbulent production and energy dissipation start with large positive values in the vicinity of the bed and decrease with an increase in vertical distance until the lower-half of the height of dune. However, all the changes in the turbulence characteristics are significant at the near-wake zones that fade away after a certain distance in the downstream. © Springer Nature Switzerland AG 2020.

GeoPlanet: Earth and Planetary Sciences

Turbulence in Wall-Wake Flow Downstream of an Isolated Dune

The saltating mode of sediment transport is the dominant mechanism of bedload transport in a fluvial stream, especially in mountainous rivers. In most simulation studies, the actual shapes of sediment particles are simplified considering the spherical shape of particles, which can affect the accuracy of the estimation of bedload transport rate. In this study, a model of sediment particle saltation by streamflow is presented, simulating the wall-shear turbulent flow over a sediment bed by large-eddy simulation and calculating the forces acting on the saltating particles by Newton's second law of motion. The model was calibrated by using the experimental data from previous studies on particle saltation. To study the impact of particle shapes, the computational results of saltation lengths, heights, and velocities of different-shaped particles were analyzed. Then, three key parameters were used to estimate bedload transport rates: bedload concentration, saltation height, and particle velocity. By summarizing the above results, this work presents a formula of bedload transport rate that improves upon a previous well-celebrated formula from the literature. The proposed formula introduces shape factors of natural sediment particles. © 2020 American Society of Civil Engineers.

Journal of Hydraulic Engineering

Impact of Particle Shape on Saltating Mode of Bedload Transport Sheared by Turbulent Flow

Fine particulate matter (PM2.5, aerodynamic diameter ≤2.5 µm) impacts the climate, reduces visibility and severely influences human health. The Indo-Gangetic Plain (IGP), home to about one-seventh of the world’s total population and a hotspot of aerosol loading, observes strong enhancements in the PM2.5 concentrations towards winter. We performed high-resolution (12 km × 12 km) atmospheric chemical transport modeling (WRF-Chem) for the post-monsoon to winter transition to unravel the underlying dynamics and influences of regional emissions over the region. Model, capturing the observed variations to an extent, reveals that the spatial distribution of PM2.5 having patches of enhanced concentrations (≥100 µgm−3) during post-monsoon, evolves dramatically into a widespread enhancement across the IGP region during winter. A sensitivity simulation, supported by satellite observations of fires, shows that biomass-burning emissions over the northwest IGP play a crucial role during post-monsoon. Whereas, in contrast, towards winter, a large-scale decline in the air temperature, significantly shallower atmospheric boundary layer, and weaker winds lead to stagnant conditions (ventilation coefficient lower by a factor of ~4) thereby confining the anthropogenic influences closer to the surface. Such changes in the controlling processes from post-monsoon to winter transition profoundly affect the composition of the fine aerosols over the IGP region. The study highlights the need to critically consider the distinct meteorological processes of west-to-east IGP and changes in dominant sources from post-monsoon to winter in the formulation of future pollution mitigation policies. © 2020, The Author(s).

Fulltext

Scientific Reports

On the widespread enhancement in fine particulate matter across the Indo-Gangetic Plain towards winter

The paper highlights the importance of using site-specific shear modulus reduction (G/Gmax versus shear strain, γ) curves and damping ratio (D versus shear strain, γ) curves for ground response analysis. In order to develop comprehensive G/Gmax–γ and D–γ curves (i.e. over a wide range of strain level), two types of apparatus, viz. resonant column and cyclic simple shear, have been used. The case study considered the geological deposits from the river beds of Yamuna River originating from the Himalayan seismic zone of North India. The tests results have been analysed to develop G/Gmax–γ and D–γ curves and compared with standard curves. It has been observed that upper and lower boundaries for the standard curves are remarkably different for the geological deposit under consideration. In order to assess the impact of using standard curves rather than site-specific curves, ground response analysis has been carried out at five sites along the Yamuna River using two types of curves (standard and site-specific developed in this study). The study showed that the amplification of shear waves at these sites based on the experimentally derived curves is much higher as compared to the standard curves. The proposed curves better represent dynamic behaviour of the soil deposits of the region and will provide a realistic response as far as practically possible, for the structures constructed in the states of Haryana and Delhi and nearby areas. It is anticipated that the data presented in this paper will have wide application and usage. © 2020, Springer Nature B.V.

Natural Hazards

Dynamic soil properties and seismic ground response analysis for North Indian seismic belt subjected to the great Himalayan earthquakes

Deformational properties, such as, Young's modulus and Poisson's ratio are considered to be among the most critical parameters of coal measure rocks for coal bed methane (CBM) extraction, CO2 sequestration, and mining activities. The inherent heterogeneity of these rocks from basin to basin makes the accurate estimation of deformational properties very complex. Here, these properties were evaluated using artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS), and compared with the traditional multiple regression analysis (MRA). Multiple index geomechanical parameters, such as, compressive strength, tensile strength, shear strength, and P-wave velocity have been used as the inputs to build the prediction models. In total 69 data sets, developed from laboratory measurements were used for the analysis. First 57 datasets were used to train the soft computing models, and the rest 12 were used to measure the accuracy and validity. Performance of the each of the statistical and soft computing models were evaluated using correlation coefficient (R2), root mean square error (RMSE), variables accounted for (VAF), and mean absolute percentage error (MAPE). Results show that ANFIS model gives the best prediction model for both the Young's modulus and Poisson's ratio. Therefore, the present study shows that it is possible to build accurate and generalized soft computing model than can incorporate heterogeneity and predict deformational properties of coal measure rocks very well without resorting to time consuming test procedures. © 2019 Elsevier Ltd

Measurement: Journal of the International Measurement Confederation

Predicting deformational properties of Indian coal: Soft computing and regression analysis approach

Groundwater for Sustainable Development

Evaluation of injection schedule for synthesizing iron-sulfide within the porous media for immobilizing arsenite: In-situ remediation approach for arsenic in groundwater

IN Patent App. 201,811,027,187

APPARATUS AND METHOD FOR MEASURING PULLOUT RESISTANCE OF A REINFORCING ELEMENT OF REINFORCED SOIL STRUCTURES

The law of the wall, regarded as one of the very few pieces of turbulence hypothesis, predicts the mean-velocity profile (MVP) in a wall-bound flow. For about nine decades, the underlying physics of the law is deemed to be governed by an ad hoc mixing-length hypothesis. Here, we seek the origin of the law, for the first time, with the aid of a new hypothesis, which we call the mixing-instability hypothesis. The hypothesis unveils the previously unknown universal scaling behavior for the amplitude of turbulent ripples or waves (that cause spontaneous stretching and shrinking of turbulent eddies) within the overlap layer and accurately maps the experimental data of the MVPs for moderate to extremely large Reynolds numbers. This study offers a new mechanism of the momentum transfer in a turbulent wall-bound flow, calling for a revision of the conventional mixing-length hypothesis, which has persisted in standard textbooks on turbulence for many decades. © 2020 Author(s).