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

A detailed measurement of rainfall is an important input to various climate models. Accuracy of rainfall measurements also has a socio-economic impact since it forms an important constituent in the region-wise and seasonal water budget. Radar measurements are most promising in this direction since they provide the detailed spatiooral data than any conventional method. However, it also has the disadvantage that rainfall estimation using radar is an indirect measurement and often involves the use of a number of correlations. The amount of scattered radiation is directly related to the raindrop size and shape distribution. Therefore, this project is aimed at solving Maxwell's equations of electromagnetism using the lattice Boltzmann method with the intention of accurately relating the size and shape distribution of falling raindrops to scattered intensity and thus improving the rainfall measurement. Towards this objective, a D3Q7 code for a pseudo vector discrete Boltzmann distribution function has been developed following the work of Hauser and Verhey (2017) [1]. Standard validations involving scattering of electromagnetic waves by a dielectric interface and a circular scatterer have been performed. Error in the solutions was found to be minimal on comparing with analytical solutions. The applicability of the proposed numerical method towards analyzing scattering of electromagnetic waves by a three-dimensional scatterer, modelled on realistic hydrometeors, will be discussed.. © 2020 IEEE.

World University root node

Department Of Chemical Engineering

Proceedings of the 2020 IEEE International Conference on Computational Electromagnetics, ICCEM 2020

A lattice boltzmann method for electromagnetic wave propagation in medium

This paper aims to estimate the enhancement in the energy absorption characteristics of the glass fiber reinforced composites (GFRP) by embedding prestrained pseudo-elastic shape memory alloy (SMA) that was used as a secondary reinforcement. The pseudo-elastic SMA (PE-SMA) embedded were in the form of wires and have an equiatomic composition (i.e., 50%-50%) of nickel (Ni) and titanium (Ti). These specimens are fabricated using a vacuum-assisted resin infusion process. The estimation is done for the GFRP and SMA/GFRP specimens at four different impact velocities (65, 75, 85, and 103 m/s) using a gas-gun impact set-up. At all different impact velocities, the failure modes change as we switch from GFRP to SMA/GFRP specimen. In the SMA/GFRP specimen, the failure mode changed from delamination in the primary region to SMA-pull out and SMA deformation. This leads to an increase in the ballistic limit. It is observed that energy absorbed by SMA/GFRP specimens is higher than the GFRP specimens subjected to the same levels of impact energy. To understand the damping capabilities of SMA embedment, vibration signals are captured, and the damping ratio is calculated. SMA dampens the vibrations imparted by the projectile to the specimen. The damping ratio of the SMA/GFRP specimens is higher than the GFRP specimens. The damping effect is more prominent below the ballistic limit when the projectile got rebounded (65 m/s).

Department of Engineering Design

Fulltext

Molecules (Basel, Switzerland)

Ballistic Impact Behaviour of Glass/Epoxy Composite Laminates Embedded with Shape Memory Alloy (SMA) Wires

Failure of bioengineered meniscus implant after transplantation is a major concern owing to mechanical failure, lack of chondrogenic capability and patient specific design. In this article, we have, for the first time, fabricated a 3D printed scaffold with carbohydrate based self-healing interpenetrating network (IPN) hydrogels-based monolith construct for load bearing meniscus tissue. 3D printed PLA scaffold was surface functionalized and embedded with self-healing IPN hydrogel for interfacial bonding further characterized by micro CT. Using collagen (C), alginate (A) and oxidized alginate (ADA), we developed self-healing IPN hydrogels with dual crosslinking (Ca2+ based ionic crosslinking and Schiff base (A-A, A-ADA)) capability and studied their physicochemical properties. Further, we studied human stem cells behaviour and chondrogenic differentiation potential within these IPN hydrogels. In-vivo heterotopic implantation confirmed biocompatibility of the monolith showing the feasibility of using carbohydrate based IPN hydrogel embedded in 3D printed scaffold for meniscal tissue development. © 2020 Elsevier B.V.

Department Of Biotechnology

Department of Ocean Engineering

International Journal of Biological Macromolecules

Meniscal tissue engineering via 3D printed PLA monolith with carbohydrate based self-healing interpenetrating network hydrogel

Polymer bi-layer systems are often exposed to different environmental service conditions which can potentially alter the mechanical properties as it approaches the glass transition temperature of an inaccessible substrate. However, since the substrate is inaccessible, it is difficult to measure or quantify the changes in these properties while in use. A methodology has been proposed in this work for prediction of glass transition temperature and Young's modulus of an inaccessible substrate in a bilayer system. The composite mechanical property of a bi-layer system is a function of the mechanical properties of coating, substrate and the depth at which it is measured. In the present work, poly-Methylmethacrylate (PMMA) coating of 900 nm is deposited on epoxy substrate. Nanoindentation experiments are conducted at different temperatures on the bi-layer system as well as on bulk PMMA. Finite element analysis has been used to obtain the material dependency of stress distribution coefficient (α) for deconvoluting the modulus of the substrate. The methodology developed by the present authors can predict the glass transition temperature as well the magnitudes of Young's modulus of an inaccessible substrate reasonably well. © 2020

Department of Mechanical Engineering

Polymer

Prediction of glass transition temperature and Young's modulus of an inaccessible polymer substrate in changing environment

Garlic (Allium sativum L.), a popular spice, has been used for decades in treating several medical conditions. Although Allicin, an active ingredient of garlic has been extensively studied on carcinogen-induced hepatotoxicity and oxidative stress in rats (Rattus norvegicus), no systematic study on the beneficial effects of generic aged garlic and specific aged garlic extract-Kyolic has been done. The present study involves rats fed chronically with two liver carcinogens, p-dimethylaminoazobenzene and phenobarbital, to produce hepatotoxicity. The aged garlic extract was characterized by UV-spectra, FTIR, HPLC and GC-MS. Biochemical and pathophysiological tests were performed by keeping suitable controls at four fixation intervals, namely, 30, 60, 90, and 120 days, utilizing several widely accepted toxicity biomarkers. Compared to the controls, remarkable elevation in the activities of lactate dehydrogenase, gamma glutamyl transferase and decline in catalase and glucose-6-phosphate dehydrogenase were observed in the carcinogen fed rats. Daily administration of aged garlic extract, could favorably modulate the elevated levels of various toxicity biomarkers including serum triglyceride, creatinine, urea, bilirubin, blood urea nitrogen except total cholesterol. It also altered the levels of blood glucose, HDL-cholesterol, albumin, AST, ALT, and hemoglobin contents in carcinogen intoxicated rats, indicating its protective potential against hepatotoxicity and oxidative stress in the experimental rats. Down-regulation of Bcl-2 and p53 proteins caused cell cycle arrest and apoptosis in garlic fed group. Kyolic exhibited additional benefits by arresting cell viability of cancer cells. This study would thus validate the use of aged garlic extract in the treatment of diseases causing liver toxicity including hepatocarcinoma.

Benefits of aged garlic extract in modulating toxicity biomarkers against p-dimethylaminoazobenzene and phenobarbital induced liver damage in Rattus norvegicus

Intersecting sprays are important to several practical applications from rocket combustion to spray painting. The characteristics of these sprays are examined using water as the working fluid. Three types of atomizer configurations are used for this study: (i) Single spray (ii) Double spray- two pressure swirl atomizers of same type, separated by a distance in the exit orifice plane and (iii) Triple spray- three pressure swirl atomizers of same type, placed on the corners of an equilateral triangle. The Sauter mean diameter, joint velocity and diameter distributions as well as the radial and circumferential liquid distribution are experimentally measured using phase doppler interferometry (PDI) technique. From these results, it is observed that at low injection pressures the liquid sheets emerge from exit orifices interacts. As the injection pressure is increased, the breakup length tends to decrease and a regime is identified where the liquid sheets and droplet clouds interfere. In this regime, the drop clouds formed from the different sheets collide with each other resulting in further increases in velocity and drop size remain unaltered. As a result, the hollow cone nature of the overall spray is transformed into solid cone spray of almost an even mean drop size distribution downstream of the spray intersection region. The study demonstrates that the dynamics of wave propagation on the liquid sheets in intersecting sprays is markedly different from the non-intersecting spray. The superimposition of diameter and velocity distribution of two or more single spray is different from the mutual intersection of multiple sprays. © 2018 Solar Turbines Incorporated.

ICLASS 2018 - 14th International Conference on Liquid Atomization and Spray Systems

Dynamics of intersecting pressure swirl sprays

Foraging and other natural phenomena show superdiffusive transport that are described by Lévy walks. We present a model experimental system, an octanoic acid (OA) drop on aqueous unsaturated OA solutions, for studying Lévy walks in controlled environments. The drop spontaneously moves due to unbalanced Marangoni forces, in a manner that mimics biological propulsion in living systems. The drop motion is shown to be a Lévy walk by demonstrating superdiffusive transport, Lévy-stable distributed step lengths, and power-law decay in the velocity autocorrelation function, with consistent exponents. © 2020 American Physical Society.

Physical Review Fluids

Lévy walking droplets

This empirical study aims to characterize the dynamical behaviour of sprays using time-series analysis of the size-velocity data acquired using a phase Doppler particle analyser. The prime motivation of this analysis is to capture the spatio-temporal correlations using time-series modelling paradigms that provide valuable new insights into spray dynamics. As a first step, we study long-held assumptions, especially on stationarity and time unsteadiness. We show that air-blast sprays have increased drop size as well as velocity ordering near the edge of the spray. Analysis of the inter-particle time of the droplets shows non-Poisson behaviour where droplets that are closely spaced in time are also closely spaced in the size and velocity coordinates. Temporal auto-correlation and partial auto-correlation calculations reveal the presence of inherent correlated features in the spray. This correlation is stronger and short lived in an air-blast spray and weaker but more persistent in a pressure swirl spray. These correlations render the probability density function (p.d.f.) estimate obtained from standard methods inaccurate; therefore, we propose a technically correct way of estimating the p.d.f. using a suitable downsampling and averaging method. Statistical analysis of residuals (from appropriate autoregressive integrated moving average time-series models) uncovers an interesting feature of spray data pertaining to heteroskedasticity (stochastically changing variance) of the diameter series. In order to account for heteroskedasticity, appropriate generalized autoregressive conditional heteroskedasticity models are developed. Finally, we present a utilitarian view of these results as an empirically consistent boundary condition implementation tool for computational fluid dynamics (CFD). © 2021 American Medical Association. All rights reserved.

Journal of Fluid Mechanics

Spatio-temporal microstructure of sprays: Data science-based analysis and modelling

Surface coatings are mainly applied to protect concrete structures against various environmental conditions. However, the interface between the concrete and coating is a weak link, and interfacial delamination is the primary mode of failure. Fracture resistance is the main design criteria for these materials, and therefore, it is necessary to investigate possible causes of interfacial failure for preventive measures. To this end, we have investigated the potential failure mechanisms and measured interfacial strength by performing a pull‐off adhesion test on epoxy coated cement paste. From the pull‐off adhesion test, adhesive (interface) failure between cement paste and epoxy is predominantly observed. It is observed that the adhesive (interfacial) strength for the sample tested on 50th day is more than the 28 days hydrated sample. This is due to additional curing of cement paste samples after coating epoxy which leads to higher interfacial strength. We also present the phase‐field model (PFM) to predict the adhesive failure for this system. The results obtained from the PFM, i.e., load at failure and crack path are validated against experimental results. Finally, the influence of various material parameters such as elastic modulus and fracture energy of the interface on interfacial fracture behaviour is studied. © The Author(s) 2021.

Department Of Civil Engineering

RILEM Technical Letters

Interfacial fracture behaviour between cement paste and epoxy coating ‐ an experimental and phase‐field approach

This work reports the growth of stable TiO2 nanotube arrays on flexible Kapton substrates by electrochemical anodization of a sputtered Ti (titanium) film. Although such nanotubes are conventionally fabricated on Ti foils, obtaining these on polymer-based flexible substrates remained a challenge because of higher annealing temperature not compatible with thermal stability of the substrates. Here, we demonstrate the fabrication of TiO2 nanotubes (1.5 μm long and 80 nm diameter) by anodization of the Ti film deposited using the RF sputtering technique at two different substrate temperatures (room temperature and 300 °C). Nanoindentation and nanoscratch techniques reveal better adhesion of the Ti film with an underlying Kapton substrate for 300 °C deposition temperature. Such investigations reveal a more than twofold enhancement of the "rear pileup"for the Ti film deposited at elevated temperature compared to that at room temperature. The amorphous TiO2 nanotubes are crystallized at 220 °C for 3 h using a solvothermal technique that allows crystallization at temperatures much lower than the annealing temperature. Application of these nanotubes for photo-electrochemical water splitting reveals a photocurrent density of 18 μA/cm2 under AM 1.5 G conditions. Furthermore, the charge density and flat band potential (VFB) are calculated from Mott-Schottky analysis, showing features comparable to the TiO2 nanotubes on the Ti foil crystallized through thermal annealing. The present work establishes a scalable approach for developing TiO2 nanotube arrays on the flexible substrate and its use for photo-electrochemical solar energy conversion. © 2020 American Chemical Society. All rights reserved.