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

Gravel-bed roughness structures for an unworked bed and a water-worked bed are analysed at different topographic scales measuring the bed surfaces by a 3D terrestrial laser scanner in a laboratory flume. The study represents a novel contribution in assessing the role of water-work on a uniform gravel-bed, demonstrating the development of small-scale bedforms (i.e. clusters). To support these observations, an in-depth statistical analysis of the bed topographies before and after water-working was applied at the grain scale and the mesoscale (i.e. a scale larger than the biggest individual particles), revealing that this is an essential prerequisite to properly interpret the roughness structures thus formed. In addition, the results show that the unworked bed is characterized by a multiscaling behavioural feature that represents multifractality of the bed roughness structure. For the water-worked bed, a simple scaling is prevalent, which implies that at small spatial lags, a statistically self-similar characteristic is preserved. © 2020 International Association for Hydro-Environment Engineering and Research.

World University root node

Journal of Hydraulic Research

Statistical characterization of unworked and water-worked gravel-bed roughness structures

National Capital Region (NCR) encompassing New Delhi is one of the most polluted urban metropolitan areas in the world. Real-time chemical characterization of fine particulate matter (PM1 and PM2.5) was carried out using three aerosol mass spectrometers, two aethalometers, and one single particle soot photometer (SP2) at two sites in Delhi (urban) and one site located ~40 km downwind of Delhi, during January–March 2018. The campaign mean PM2.5 (NR-PM2.5 + BC) concentrations at the two urban sites were 153.8 ± 109.4 μg.m−3 and 127.8 ± 83.2 μg.m−3, respectively, whereas PM1 (NR-PM1 + BC) was 72.3 ± 44.0 μg.m−3 at the downwind site. PM2.5 particles were composed mostly of organics (43–44)% followed by chloride (14–17)%, ammonium (9–11)%, nitrate (9%), sulfate (8–10)%, and black carbon (11–16)%, whereas PM1 particles were composed of 47% organics, 13% sulfate as well as ammonium, 11% nitrate as well as chloride, and 5% black carbon. Organic aerosol (OA) source apportionment was done using positive matrix factorization (PMF), solved using an advanced multi-linear engine (ME-2) model. Highly mass-resolved OA mass spectra at one urban and downwind site were factorized into three primary organic aerosol (POA) factors including one traffic-related and two solid-fuel combustion (SFC), and three oxidized OA (OOA) factors. Whereas unit mass resolution OA at the other urban site was factorized into two POA factors related to traffic and SFC, and one OOA factor. OOA constituted a majority of the total OA mass (45–55)% with maximum contribution during afternoon hours ~(70–80)%. Significant differences in the absolute OOA concentration between the two urban sites indicated the influence of local emissions on the oxidized OA formation. Similar PM chemical composition, diurnal and temporal variations at the three sites suggest similar type of sources affecting the particulate pollution in Delhi and adjoining cities, but variability in mass concentration suggest more local influence than regional. © 2021 Elsevier B.V.

Science of the Total Environment

Real-time characterization and source apportionment of fine particulate matter in the Delhi megacity area during late winter

Delhi is one of the most polluted cities globally, with frequent severe air pollution episodes and haze events occurring in recent years, thereby compelling us to understand the sources to develop effective mitigation plans. Complete chemical characterization of fine particulate matter (PM2.5) components (non-refractory, refractory and elements) with high time resolution has been done during the summer season (June-July 2019). The total PM equivalent (PM2.5(eq)) was 28.7 +/- 13.2 mu g m(-3) of which elements dominated the PM2.5(eq) with 34\% contribution followed by organics (28\%), black carbon (BC) (17\%), SO42- (10\%), Cl (5\%) NH4+ (3.5\%) and NO3- (2.5\%). The contributions from organic aerosols (OA) and SO42- were observed to be more than Cl- and NO3-. The total elemental mass concentration (PMEl) was mostly contributed (similar to 96\%) by Si, S, Cl, Ca, K, Fe and Al with Si and S alone contributing around 50\% of PMEl. Crustal elements (Al, Fe, Ca and Si) were highly enhanced in summer than elements emitted from anthropogenic emissions (Cl, S, K, Pb and Zn). Source apportionment (SA) of PM was performed using positive matrix factorization (PMF) together with ME-2 (multilinear engine) for OA and elements, separately. PMF on both datasets helped resolve sources such as combustion, industrial, dust-related, incineration and traffic. OA PMF identified three factors related to primary emissions: hydrocarbon-like OA (HOA, 12.3\%), solid fuel combustion (SFC, 16.2\%) and cooking OA (COA, 7.3\%) and two oxygenated OA (OOA): semi-volatile OOA (SVOOA, 15.2\%) and low-volatile OOA (LVOOA, 49.1\%). The elemental PMF resolved 8 factors: dust (52.5\%), S-rich (16.2\%), Cl-rich (10.7\%), 2 SFC factors (10.5\%), non-exhaust (7.2\%), Cu-rich (1.5\%) and industrial (1.4\%). The contribution of BC to total PM mass is shown to increase in the summer compared to previous studies reported for the winter season. The secondary oxidized sources dominated both the OA and elements SA during the summer with 64.3\% and 27\% (dust not considered) contribution, respectively. The domination of secondary sources implies that it is crucial to control the secondary aerosols' precursors in Delhi for developing pollution control strategies. The ME-2 resolved factors, coupled with concentration weighted trajectory (CWT) showed the probable major elemental source regions of local origin (Delhi- National Capital Region (Delhi-NCR)) as well as regional (from Punjab, Haryana, Uttar Pradesh and Pakistan). The local sources included Cu-rich (Haryana) and SFC-II (Delhi and Uttar Pradesh), while the regional sources were dust (southwest (SW)), industrial, Cl-rich (north-west (NW)), SFC-I (east and south-east (SE)) and S-rich (SE).

ATMOSPHERIC ENVIRONMENT

Real-time quantification and source apportionment of fine particulate matter including organics and elements in Delhi during summertime

Rutting and fatigue are two major pavement distresses which affect both structural and functional performances of the flexible pavement. Linear amplitude sweep (LAS) and Multiple stress creep and recovery (MSCR) are two advanced methods to examine fatigue and rutting performance of asphalt binders respectively. The present study aims at examining the effect of ageing (short term and long term) and modification (polymer and warm mix) on the performance of asphalt binders. Both LAS and MSCR tests were conducted at different temperatures, stress/strain levels, and ageing conditions. Stress is a parameter that influences the performance of asphalt binder significantly so stress susceptibility was also evaluated for all the binders at different temperatures and ageing conditions. From the test results, it was found that ageing improves the stress susceptibility of the asphalt binders with respect to rutting parameters on the other hand ageing deteriorated the stress susceptibility concerning fatigue parameters. The applicability of different asphalt binders at different temperature and traffic conditions was also examined and it was found that most of the binders failed to fulfill the criteria at the temperatures which were well below their high-temperature performance grades. This highlighted the need to revise the Superpave criteria. © 2021, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.

International Journal of Pavement Research and Technology

Rutting and Fatigue Performance of Aged Modified Asphalt Binders

Flash droughts cause rapid depletion in root-zone soil moisture and severely affect crop health and irrigation water demands. However, their occurrence and impacts in the current and future climate in India remain unknown. Here we use observations and model simulations from the large ensemble of Community Earth System Model to quantify the risk of flash droughts in India. Root-zone soil moisture simulations conducted using Variable Infiltration Capacity model show that flash droughts predominantly occur during the summer monsoon season (June–September) and driven by the intraseasonal variability of monsoon rainfall. Positive temperature anomalies during the monsoon break rapidly deplete soil moisture, which is further exacerbated by the land-atmospheric feedback. The worst flash drought in the observed (1951–2016) climate occurred in 1979, affecting more than 40% of the country. The frequency of concurrent hot and dry extremes is projected to rise by about five-fold, causing approximately seven-fold increase in flash droughts like 1979 by the end of the 21st century. The increased risk of flash droughts in the future is attributed to intraseasonal variability of the summer monsoon rainfall and anthropogenic warming, which can have deleterious implications for crop production, irrigation demands and groundwater abstraction in India.

Fulltext

npj Climate and Atmospheric Science

Anthropogenic warming and intraseasonal summer monsoon variability amplify the risk of future flash droughts in India

Droughts in South Asia pose substantial challenges to water resources, agricultural and socio-economic growth of more than two billion people. However, the most detrimental soil moisture droughts, their impacts and occurrence in the observed and projected climate in South Asia remain unidentified. We conducted soil moisture simulations using the variable infiltration capacity model and meteorological forcing based on the four global observational products (Climate Research Unit, WATCH-Forcing-Data-ERA-Interim, University of Delaware and Princeton) to identify the worst soil moisture drought during 1951-2016. The worst soil moisture drought during the observed record occurred in 2002 and affected more than 65% of South Asia and resulted in a decline in rice yield (∼400 kg ha-1). A large uncertainty based on the four observational products was found in the number of drought spells and their characteristics. We estimated the frequency of droughts that exceeded the overall severity score of the worst drought during 1951-2016 under the future climate using 40 simulations from Community Earth System Model-Large Ensemble. The frequency of the worst droughts is projected to increase by about 1.5 times in the future (2035-2100) in comparison to the historic (1951-2016) climate. The worst droughts in the future are likely to be more intense and widespread in South Asia. A considerable influence of industrial aerosols was found on the occurrence of the worst droughts in South Asia. Our findings have implications for food and water security in one of the most densely populated regions in the world.

Environmental Research Letters

On the occurrence of the worst drought in South Asia in the observed and future climate

In this paper, we explore the mega riverbed-patterns, whose longitudinal and vertical length dimensions scale with a few channel widths and the flow depth, respectively. We perform the stability analyses from both linear and weakly nonlinear perspectives by considering a steady-uniform flow in an erodible straight channel comprising a uniform sediment size. The mathematical framework stands on the dynamic coupling between the depth-averaged flow model and the particle transport model including both bedload and suspended load via the Exner equation, which drives the pattern formation. From the linear perspective, we employ the standard linearization technique by superimposing the periodic perturbations on the undisturbed system to find the dispersion relationship. From the weakly nonlinear perspective, we apply the centre-manifold-projection technique, where the fast dynamics of stable modes is projected on the slow dynamics of weakly unstable modes to obtain the Stuart-Landau equation for the amplitude dynamics. We examine the marginal stability, growth rate and amplitude of patterns for a given quintet formed by the channel aspect ratio, wavenumber of patterns, shear Reynolds number, Shields number and relative roughness number. This study highlights the sensitivity of pattern formation to the key parameters and shows how the classical results can be reconstructed on the parameter space. © 2021 The Authors.

Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences

Mega riverbed-patterns: Linear and weakly nonlinear perspectives

In this paper, we explore the hydrodynamic instability of free river bars driven by a weakly varying turbulent flow in a straight alluvial channel with erodible bed and non-erodible banks. We employ linear stability analysis in the framework of depth-averaged formulations for the hydrodynamics and the sediment transport. A significant fraction of the sediment flux is considered to be in suspension. The analysis is performed for the alternate pattern of river bars at the leading order followed by the next order, covering the effects of flow regime. We find that the unstable region bounded by a marginal stability curve depends significantly on the shear Reynolds number, which demarcates different flow regimes, and the Shields number and the relative roughness (particle size to flow depth ratio). The results at the next order stabilize the bars with longer wavenumbers. The variations of threshold aspect ratio with Shields number and relative roughness are studied for different flow regimes. In addition, for a given Shields number and relative roughness, the diagram of threshold aspect ratio vs shear Reynolds number is explained. Unlike the conventional theories of bar instability, the analysis reveals limiting values of Shields number and relative roughness beyond which the theoretical results at the next order produce infeasible regions of instability. The limiting values of Shields number and relative roughness appear to reduce, as the shear Reynolds number increases. © 2021 Author(s).

Physics of Fluids

Hydrodynamic instability of free river bars

Numerical simulation of undular hydraulic jumps, which occur at an inflow Froude number slightly above unity, remain an important and enigmatic challenge in hydraulic engineering. In this study, a systematic assessment of the two-dimensional (2D) Reynolds averaged Navier Stokes-volume of fluid (RANS-VOF) equations coupled with the k-ω shear stress transport (SST) turbulence model was carried out for the simulation of undular jumps. The modeling strategies adopted for obtaining a stable undular jump profile are highlighted in this paper. The correlation between turbulence intensity at the jump toe and jump characteristics is also demonstrated. Comparison of laboratory observations with results obtained from experiments conducted under different discharge, approach Froude number, and inflow conditions demonstrated that the proposed 2D RANS model can accurately reproduce the key free-surface characteristics corresponding to undular jumps. The model was capable of reproducing the velocity and pressure fields with greater accuracy than the depth-averaged model. The model was also successful in reproducing the bottom recirculation region below the first wave crest for undular jumps with partially developed boundary layer at the jump toe. The proposed 2D RANS-VOF computational fluid dynamics (CFD) model coupled with the k-ω SST turbulence closure equation is, therefore, recommended as an efficient tool for hydraulic computations, especially for the simulation of weak undular jumps. © 2021 American Society of Civil Engineers.

Journal of Hydraulic Engineering

Undular Hydraulic Jumps: Critical Analysis of 2D RANS-VOF Simulations

This paper discusses on the choice of a recently proposed multi-class, speed-area occupancy based, one-dimensional continuum model towards the measurement of network level traffic flow variables, namely, travel time and outflow. The parameters of the model are calibrated for a hypothetical mid-block with four vehicle classes, using the micro simulation data from VISSIM software. Analysis result indicates that the model produces travel time and outflow result closer to that by the VISSIM micro simulation. To explore this macroscopic model towards accurate modelling of lacking lane disciplined traffic, i.e. the traffic with frequent lateral movements, a two-dimensional formulation of the model is proposed. It is shown that the new formulation retains the properties of its original version as well as the desirable properties of any traffic flow model. © 2019 Informa UK Limited, trading as Taylor & Francis Group.

International Journal of Modelling and Simulation

Multi-class AR model: comparison with microsimulation model for traffic flow variables at network level of interest and the two-dimensional formulation