IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

The extent of dissolution of petroleum hydrocarbon fuels into groundwater depends greatly on fuel composition. Petroleum fuels can consist of thousands of compounds creating different interactions within the non-aqueous phase liquid (NAPL), thereby affecting the relative dissolution of the components and hence a groundwater plume's composition over long periods. Laboratory experiments were conducted to study the variability in the effective solubilities and activity coefficients for common constituents of gasoline fuels (benzene, toluene, p-xylene and 1,2,4-trimethylbenzene) (BTX) in matrices with an extreme range of molar volumes and chemical affinities. Four synthetic mixtures were investigated comprising BTX with the bulk of the NAPL mixtures made up of either, ethylbenzene (an aromatic like BTX with similar molar volume); 1,3,5-trimethylbenzene (an aromatic with a greater molar volume); n-hexane (an aliphatic with a low molar volume); and n-decane (an aliphatic with a high molar volume). Equilibrium solubility values for the constituents were under-predicted by Raoult's law by up to 30% (higher experimental concentrations) for the mixture with n-hexane as a filler and over-predicted by up to 12% (lower experimental concentrations) for the aromatic mixtures with ethylbenzene and 1,3,5-trimethylbenzene as fillers. Application of PP-LFER (poly-parameter linear free energy relationship) model for non-ideal mixtures also resulted in poor correlation between experimentally measured and predicted concentrations, indicating that differences in chemical affinities can be the major cause of deviation from ideal behavior. Synthetic mixtures were compared with the dissolution behavior of fresh and naturally weathered unleaded gasoline. The presence of lighter aliphatic components in the gasoline had a profound effect on estimating effective solubility due to chemical affinity differences (estimated at 0.0055 per percentage increase in the molar proportion of aliphatic) as well as reduced molar volumes (estimated at −&nbsp;0.0091 in the activity coefficient per unit increase in molar volume, mL/mol). Previously measured changes in activity coefficients due to natural weathering of 0.25 compares well to 0.27 calculated here based on changes in the chemical affinity and molar volumes. The study suggests that the initial estimation of the composition of a fuel is crucial in evaluating dissolution processes due to ideal and non-ideal dissolution, and in predicting long term dissolution trends and the longevity of NAPL petroleum plume risks. © 2016 Elsevier B.V.

World University root node

Department Of Civil Engineering

Department of Ocean Engineering

Department Of Chemical Engineering

Journal of Contaminant Hydrology

Effect of compositional heterogeneity on dissolution of non-ideal LNAPL mixtures

Pesticides are a major source of environmental concern due to their persistence and health and ecological impacts, particularly in developing countries. Heterogeneous photocatalysis has emerged as a promising technique for their removal from wastewaters. But effective implementation requires the development of efficient and practical photocatalytic systems. A novel photo reactor was developed in this study using TiO2-coated polymeric beads as floating catalysts which enabled efficient penetration of UV radiation; good mixing and high mass transfer rates. The performance of the immobilised bead photo reactor was evaluated for the removal of an organophosphate pesticide—monocrotophos. Batch studies were carried out using a 23 central composite factorial design of experiments, with initial pesticide concentration (1–15 mg/l), initial pH (3.5–10.5), and catalyst loading (2–6 g/l) as process variables. About 50–80% degradation was achieved depending on the levels of initial pesticide concentration, pH, and the amount of catalyst. A quadratic polynomial model was fitted to the experimental removal efficiency and the statistical analysis revealed that the coefficients for the main effects are significant. © 2016 Balaban Desalination Publications. All rights reserved.

GENERAL

Desalination and Water Treatment

Optimization studies on degradation of monocrotophos in an immobilized bead photo reactor using design of experiment

The traditional Vishu festival in the state of Kerala in South India is celebrated in April with extensive coordinated fireworks display. The influence of these celebrations on the immediate and long-term air quality and impact on the health and well being of the public needs research. The combustion clouds contain harmful fumes (sulfur dioxide, oxides of nitrogen) and particulate matter released at the surface. This study is focused on the influence of fireworks on the air quality at Kannur, India, during Vishu in April 2010 and 2011. Elevated concentrations of various air pollutants such as O 3, NO 2, NO and PM 10 were measured during the intense usage of fireworks. Surprisingly, the organic analysis of the Particulate Matter (PM) samples collected on Vishu day revealed the emission of a variety of hazardous organic compounds during the fireworks display. One of the unique observations in this work is the nighttime production of O 3 by the photodissociation of NO 2 from the flash of firecrackers. The concentration of O 3 was observed to increase two fold over the control days of observation during the same month. Moreover, the concentrations of NO 2, and PM 10 increased by 100%. The concentration of NO was reduced by four fold during the event. A scheme based on the organic combustion from fireworks and peroxyl radical mediation is proposed for the nighttime production of ozone. The diurnal profile of all pollutants except NO showed higher concentrations starting from the Vishu eve on April 14 to Vishu day on April 15 and this pattern repeated for years 2010 and 2011. The fireworks activities have been increasing every year and generation of pollutants at their increased levels for short duration can potentially cause adverse health impacts on a regional scale in a highly populated region. © 2011 Elsevier Ltd.

Atmospheric Environment

Atmospheric pollution in a semi-urban, coastal region in India following festival seasons

Atmospheric aerosols are important from a perspective of ambient air pollution and health to humans and other biological receptors as well as for potential effects on local weather and global climate. This review attempts to account for the different research efforts of individual research groups and regulatory agencies in India on the issue of atmospheric aerosols and their effects. The review refers to representative studies reporting the physical characterization (size), chemical composition (organic and inorganic), radiative forcing effects and health effects of aerosols. There are several reports on source apportionment studies identifying sources of aerosols and some focus on specific issues. The review also points out a significant need for more data with a greater spatial and temporal resolution for better understanding of the dynamics of atmospheric aerosols in the Indian context.

Current Science

Current atmospheric aerosol research in India

In the present work, a complete algorithm is presented to simulate the gas exchange process across domains in a multi-block computation involving a piston-controlled port. The moving boundary scheme of Peric is used in conjunction with the zonal boundary scheme of Rai. The algorithm has been applied to two cases. The first case involves a typical air-filling process through the piston-operated port of a pneumatic pump, and the analysis shows that flowfield variable information is smoothly communicated across the zonal boundary using this algorithm. The second case involves modelling of the scavenging process in a loop-scavenged two-stroke internal combustion (IC) engine. In this case, the stepwise evolution of the scavenging flow in the engine cylinder is studied. Initiation of short circuiting at early stages of scavenging, tilting of the inlet flow in directions different from inlet port angles and the existence of a low-purity swirling loop in the exhaust-side top corner of the engine cylinder are observed from the flowfield computations.

Department of Mechanical Engineering

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

Multidimensional modelling of flow through piston-controlled ports using a multi-block, moving mesh algorithm

The pressure-time characteristics for the charging process of a cylinder with a piston-controlled port through a connecting duct is studied with the objective of assessing the accuracy of various methods such as the lumped parameter or zero-dimensional approach, an intermediate hybrid approach and a full three-dimensional computational fluid dynamics (CFD) calculation. The predictions from all the approaches are compared with experimental data. It is observed that, for a particular cup-shaped geometry of the piston, both the zero-dimensional and hybrid approach overpredict the pressure recovery rate in comparison with the three-dimensional CFD calculation, which is in good agreement with the experimental pressure-time variation. On the other hand, the agreement between the lumped parameter approach and the detailed CFD calculation is better for a flat piston, indicating the importance of the piston geometry.

Assessment of zero-dimensional, hydbrid and multidimensional simulations for transient air flow through a cylinder-duct assembly

A model is developed based on Lagrangian-drop and Eulerian-fluid procedure to simulate fuel spray structure and the interaction of spray with in-cylinder gas motion. The hollow cone spray is modeled assuming the sheet consisting of blobs of droplets and these blobs are further subjected to secondary breakup. The droplet equations of position, momentum and temperature have been solved by the fourth order Runge-Kutta scheme. The gas phase compressible flow is solved using the finite volume method in conjunction with the SIMPLEC algorithm. The coupling between gas phase and the liquid phase has been achieved through the source terms arising in each phase. Three-dimensional spray and interaction with air motion inside the cylinder have been performed. The results show that the spray structure is well simulated. The model predicts the entrained air velocities and the fuel vapour concentration distribution as a function of time. Copyright © 2001 Society of Automotive Engineers, Inc.