Department of Applied Mechanics

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

Gas entrainment in cold pool of fast reactors, induced by partially submerged pump shafts is studied by experimental and computational simulations. The model is a partially filled annular tank with a rotating shaft at the centre. The rotational Reynolds number (Re) has been varied and the resulting gas entrainment due to various mechanisms has been characterized. It is found that the fluid dynamics in the annular region can be classified into four regimes that occur with increasing Reynolds number. In the first regime encountered at low Re, there is no risk of gas entrainment. In the second regime, mild gas entrainment takes place due to the shearing at the free surface between two opposite vortices. In the third regime, gas entrainment is almost absent due to weakening of flow mechanism of the second regime. In the fourth regime, vortex break down is observed at the rotating shaft leading to large scale gas entrainment. © 2020

World University root node

Annals of Nuclear Energy

Experimental and computational investigations of gas entrainment in SFR due to rotation of partially submerged pump shaft

Nuclear reactor containment flows are primarily driven by density differences in the long term of a severe accident. It is crucial to predict such flows from the perspective of reactor safety. The present work addresses the assessment of open-source CFD code OpenFOAM in modelling buoyancy-driven turbulent flows and heat transfer relevant for analyzing the flow and mixing in a nuclear reactor containment during severe accident scenarios. A fully compressible solver with the k-ω based shear stress transport (SST) turbulence model was utilized to simulate the two-dimensional turbulent flow of a differentially heated square cavity(h   0.75, Ra   109) and then against the technical scale THAI-TH21 natural convection test (60 m3, h   9 m, Ra   1012). The results from the current study, emphasize the importance of considering radiation phenomenon in buoyancy-driven flows and the grid resolution needed in the near-wall region to accurately predict wall heat flux. Overall, the simulation results of time-averaged temperature and velocity profiles in the quasi-steady state compare very well with experimental data. The predicted values of external wall heat transfer rates on the THAI vessel, the convective wall heat flux in the gas region, and the impact of buoyancy on turbulence are discussed. © 2020 Elsevier B.V.

Department of Ocean Engineering

Nuclear Engineering and Design

CFD modelling of buoyancy driven flows in enclosures with relevance to nuclear reactor safety

We study the normal fluctuations of an MCF-7 cell membrane and calibrate the optical trap to detect pitch motion to get information about the rocking motion of a birefringent particle. We could show both theoretically and experimentally that the Z power spectrum has a power-law behavior of (frequency)-5/3, and We find that the power spectrum of slope fluctuations is proportional to (frequency)-1. We could extract parameters like bending rigidity directly from the power spectrum fitting parameters in 5 Hz to 1 kHz range. Our method was powerful enough to identify pitch rotation for a spherical birefringent particle to a high resolution using optical tweezers. © COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.

Department Of Physics

Proceedings of SPIE - The International Society for Optical Engineering

Determination of local cell membrane slope fluctuations using the pitch rotational mode of optical tweezers

Riverine systems play an important role in the global carbon cycle, and they are considered hotspots for bacterial activities such as organic matter decomposition. However, our knowledge about these processes in tropical or subtropical regions is limited. The aim of this study was to investigate anthropogenically induced changes of water quality, the distribution of selected pharmaceuticals, and the effects of pollution on greenhouse gas concentrations and bacterial community composition along the 800 km long Cauvery river, the main river serving as a potable and irrigation water supply in Southern India. We found that in situ measured pCO2 and pCH4 concentrations were supersaturated relative to the atmosphere and ranged from 7.9 to 168.7 μmol L-1, and from 0.01 to 2.76 μmol L-1, respectively. Pharmaceuticals like triclosan, carbamazepine, ibuprofen, naproxen, propylparaben, and diclofenac exceeded warning limits along the Cauvery. Proteobacteria was the major phylum in all samples, ranging between 26.1% and 82.2% relative abundance, and it coincided with the accumulation of nutrients in the flowing water. Results emphasized the impact of industrialization and increased population density on changes in water quality, riverine carbon fluxes, and bacterial community structure. © 2020 by the authors.

Department Of Civil Engineering

Fulltext

Water (Switzerland)

Anthropogenic impact on tropical perennial river in south India: Snapshot of carbon dynamics and bacterial community composition

Numerical investigations of heat transfer and fluid flow have been carried out to study the effect of variation of longitudinal and transverse pitch-to-diameter ratios for a cross-flow heat exchanger with elliptical tubes. A total of 17 configurations of varying compactness are investigated. This investigation also covers the effect of aspect ratio (0.40, 0.53, 0.78, 0.92, and 1.00) and tube arrangement (inline and staggered) on the performance of a cross-flow heat exchanger. Details of heat transfer, friction factor, goodness factor and heat transfer per unit pumping power of (3 × 5) elliptic tube bundle are evaluated in the Reynolds number range of 5,500–14,500. Based on these criteria, weighed by the compactness, the configurations with the longitudinal and transverse pitch-to-diameter values of (2:1.75) and (1.75:2) are recommended. © 2020 Taylor & Francis Group, LLC.

Department of Mechanical Engineering

Heat Transfer Engineering

Flow and Heat Transfer Characteristics of a Cross-Flow Heat Exchanger with Elliptical Tubes

Increasing terror attacks and development of improvised explosive devices (IEDs) has resulted in the development of protective structures for armoured personnel vehicles (APV). Protective members like flat steel plates are susceptible to damage due to blast load and have been already explored. As an improvement, composite plate having steel with coatings of hyperplastic materials like polyurea, for enhancing the blast mitigation, is being explored. These coated metallic plates can deflect away and absorb a major part of the blast load. One of the objectives of this work is to develop numerical methods for blast loading of structures using Abaqus explicit and validate the results against published results. These validated methods can be used for assessing the effectiveness of protective structures like V-plate with polyurea coating under blast loading. In this work, the main focus is on numerical simulation of the mechanical response of the V-shaped plate. The validation studies cover blast load generation and its interaction with V-shaped plates with and without polyurea coatings and its comparison with results reported in the literature. It is observed that blast functions can adequately model the shock waves generated in the blast loading. The latter part studies the impulse transmitted and deformations. The numerical work was carried out with a full-scale V-shaped plate made of mild steel (and having a projected dimension of about 2500 &times; 2500 mm), having polyurea coatings of 16&nbsp;mm, 16 &times; 2&nbsp;mm and 16 &times; 4&nbsp;mm thickness. The impulse transmitted to the base structure was compared with a V-plate without coating and reduction in the transmitted impulse was observed. It is assumed that the above results may be helpful in obtaining optimized plate designs. &copy; 2020, Springer Nature Singapore Pte Ltd.

GENERAL

Lecture Notes in Mechanical Engineering

Effectiveness of Polyurea Coated Steel Plates in Blast Mitigation in Vehicles

A hybrid Brain Computer Interface (BCI) system is developed using steady state visual evoked potential (SSVEP) along with the video-oculogram (VOG). The keyboard layout is designed with 23 characters flickering at selected frequencies. The template matched webcam images provide the direction of eye gaze information to localize the user gazing space on the visual keyboard/display. This spatial localization helps to use/make multiple stimuli of the same frequency. The canonical correlation analysis (CCA) is used for SSVEP frequency recognition. The experiments were conducted on 8 subjects for both online and offline analysis. Based on the classification accuracy from offline analysis, the subject specific SSVEP stimulus duration and the optimal number of EEG channels were selected for online analysis. An average online classification accuracy of 93.5% was obtained with the information transfer rate (ITR) of 96.54Â&nbsp;bits/min without inter character identifying delay. When a delay of 0.5 s is introduced between stimulus window the ITR of 80.17Â&nbsp;bits/min is realized. © Springer Nature Switzerland AG 2020.

Advances in Intelligent Systems and Computing

A visual spelling system using SSVEP based hybrid brain computer interface with video-oculography

Thermal transport in graphene is strongly influenced by strain. We investigate the influence of biaxial tensile strain on the thermal conductivity of zigzag and armchair graphene (AG and ZG) using non-equilibrium molecular dynamics simulations (NEMD). We observe that the thermal conductivity is significantly reduced under strain with a maximum reduction obtained at equi-biaxial strain. It is interesting to note that the high lateral to longitudinal strain ratios reduce the negative impact of strain on the thermal conductivity of AG and ZG. The in-plane acoustic modes are found to be the major heat carriers in unstrained graphene but are severely softened due to strain, and hence, their contribution to the conductivity drops down significantly. Strain alleviates the out-of-plane fluctuations in graphene and the group velocity of the out-of-plane acoustic mode (ZA) increases due to the linearisation of its dispersion relation. These factors result in the dominance of ZA mode in the thermal transport of strained graphene. Significant increase in the size dependence of the thermal conductivity of strained graphene is observed, which is attributed to the long-wavelength ZA phonons. The discrepancies between the results of BTE studies and NEMD are also discussed. This study suggests that biaxial strain can be an effective method to tune the thermal transport in graphene. Our findings can lead to better phonon engineering of graphene for various nanoscale applications.

Department Of Chemical Engineering

Thermal conductivity of graphene under biaxial strain: an analysis of spectral phonon properties

In the originally published article,1 the symbol τhb was not properly rendered in Figs. 5–7. The corrections to the individual figures are given below. The label to the x-axis in Fig. 5(b) of the original article1 should be “τhb (ps).” Including this rectification, Fig. 5 should be read as given below. (Figure Presented). © 2020 EDP Sciences. All rights reserved.

Journal of Chemical Physics

Erratum: The effect of temperature on water desalination through two-dimensional nanopores (J. Chem. Phys. (2020)152 (164701) DOI: 10.1063/1.5143069)

The present study investigates the fluid flow and heat transfer characteristics in a 180∘ bend domain with a bypass in the divider section using an in-house code based on Streamline Upwind Petrov-Galerkin Finite Element Method. The ratio of the inlet height to outlet height (IOR), location of the bypass (Lbyp) and Reynolds number (Re) are the parameters considered to assess the effects of heat transfer in a 180∘ bend. Flow in three IOR geometries i.e., IOR 1:2, 1:1, 2:1 with three Lbyp (−7, −5, −3) and Re in the range of 100–900 is investigated. IOR and Lbyp significantly affect the flow transitions from steady-state to periodic unsteady and finally to chaotic unsteady state. In this study, it is established that the IOR-bypass combination augments the heat transfer and decreases the pressure drop, which has been quantified using Thermal Performance Factor (TPF) and Nusselt number distribution (Nu). The increase in Nu and TPF for IOR 1:2 and 2:1 domains is higher than IOR 1:1 domains. A three-dimensional unsteady state investigation at Re=300 is also performed for IOR 1:2 with Lbyp=−7 to understand the convection of 3D vortices in the span-wise direction and its influence on heat transfer. From the 3D study, it is concluded that though the vortex shedding in the streamwise direction is similar to the 2D case, the spatial arrangement of 3D vortices along the span-wise direction is irregular at any given instant, which results in variable temperature and Nu distribution in the domain. © 2020