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

Differences in the dynamics and transport of blood make certain regions of the arterial network the preferred sites for initiation and formation of arterial diseases like stenosis and aneurysms. Understanding of such arterial diseases is directly linked to critical hemodynamic parameters such as the wall shear stress (WSS). The present work generalises the influence of WSS on the concentration of LDL that was observed in an earlier study. To this end, a wide variety of simplified flow domain, inspired by the near-wall regions of aneurysms and stenosis, are constructed and analyzed. The effects of pulsatile inflow condition, rheology of blood and curvature of the wall on the correlation between WSS and LDL concentration are investigated. It is demonstrated that the time-scale of variation of lumen-surface-concentration (LSC) of LDL is larger than a single cardiac cycle. As a consequence, the time-average values of WSS are sufficient to locate the regions of higher LSC. This idea is strengthened by making use of simplified flow domain that generates moving stagnation point. Further, it was observed that the rheology of the blood and curvature of the wall does not affect the observed correlation between the WSS and LDL concentration. © 2021 Informa UK Limited, trading as Taylor &amp; Francis Group.

Department of Mechanical Engineering

World University root node

Computer Methods in Biomechanics and Biomedical Engineering

A study on the transport and interaction between blood flow and low-density-lipoprotein in near-wall regions of blood vessels

Recent literature has shown that the spectral characteristics of a harvester can be significantly improved by invoking internal resonance between the modes. Taking motivation from this premise, the present work analyzes the nonlinear dynamics and harvesting performance of a 1:3 internally resonant piezoelectric cantilever beam with a lumped mass under harmonic excitation. The governing modal equations are derived using Galerkin's approach and Hamilton's principle of least action. The method of multiple scales has been used to study the dynamics of the harvester in the proximity of primary resonances. The steady state periodic responses of the harvester are obtained using a pseudo-arc continuation technique and subsequently, their implications on the harvested power are discussed. The frequency responses of the harvested power are shown to boast significantly high magnitudes across a wide frequency band due to the energy transfer between the modes near the primary resonances. Results presented in the study show that the higher mode invoked through internal resonance plays a significant role in broadband power generation. The transfer of energy between the modes is found to occur only within a certain threshold of excitation level which in turn affects the magnitude of harvested power. Numerical simulations have also been carried out the results of which are compared against the analytical results. The outcomes of this first-hand analysis shall aid in the proposition of an efficient design for a broadband energy harvester.

Department Of Physics

Mechanical Systems and Signal Processing

Exploring 1:3 internal resonance for broadband piezoelectric energy harvesting

We show that electrically poled ferroelectric matrix considerably enhances the localized magnetostrictive deformations in a ferroelectric-ferrimagnetic composite. Magnetostrain measurements performed on Dy-free and Dy-modified BiFeO3-PbTiO3 (BF-PT) ferroelectric ceramics revealed no measurable macroscopic strain in poled and unpoled Dy-free nonferromagnetic specimens. Dy-modified BF-PT, on the other hand, exhibit ferrimagnetic dysprosium-iron garnet (DyIG) as precipitates and exhibit a macroscopic strain of -4 ppm in the poled state. Despite the small (6%) volume fraction of DyIG, the macroscopic strain in Dy-modified BF-PT is almost 50% of the strain of pure DyIG. Our results suggest that the amplification of the localized magnetostrictive deformation in the ferrimagnetic islands by the neighboring ferroelectric regions is caused by the magnetostrictive stress-induced motion of ferroelectric-ferroelastic domains of the poled ferroelectric matrix. © 2021 American Physical Society.

Department of Management Studies

Physical Review B

Strain transfer in ferroelectric-ferrimagnetic magnetoelectric composite

This manuscript investigates the snap-through characteristics of a special class of hybrid bistable symmetric laminate (HBSL) subjected to different loading constraints and imperfections. Understanding the behavior under various loading conditions and constraints is necessary to deploy these bistable laminates in structural applications. Towards that, detailed experimental and numerical studies are done to capture the load–displacement characteristics of: (a) an HBSL clamped at different distances at one end, (b) an HBSL clamped at one end subjected to loading at different positions, and (c) HBSL with geometric imperfection concerning the laminae thicknesses. The insights from the numerical and experimental studies are subsequently used to demonstrate the importance of the snap-through characterization in designing a smart actuation system. © 2020 Elsevier Ltd

Composite Structures

Hybrid bistable composite laminates for structural assemblies: A numerical and experimental study

A robust and a compact fiber optic spectral domain low coherence interferometry system for sensing biological analytes in the biological media such as aqueous humor and gingiva, for non-invasive clinical applications has been proposed in this work. A dual wavelength approach employing two SLED sources with centre wavelengths at 1310 nm in the second overtone and 1589 nm in the first overtone region based on vibrational infrared spectroscopy for selective detection of the analyte is presented. Spectral domain low coherence interferometry provides rapid depth scanning by eliminating interference from neighbouring structures, thereby making it suitable for real time analysis. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Department of Engineering Design

Springer Proceedings in Physics

Optical Fiber Based Dual Wavelength Spectral Domain Low Coherence Interferometry for Biomedical Applications

Lead-free Na0.4K0.1Bi0.5TiO3 (NKBT) and NiFe2O4 (NFO) ceramics are synthesized by solid-state reaction, and the laminated NKBT/NFO composites have been prepared by gluing the sintered discs with silver-epoxy. The measured parameters, dielectric constant (ε′) ∼1450 at 1 kHz, remanent polarization (Pr)∼39 μC/cm2, coercive electric field (Ec)∼27 kV/cm and maximum strain (Smax)∼0.3 % of NKBT along with saturation magnetization (Ms)∼49 emu/g, coercive magnetic field (Hc)∼27 Oe and magnetostriction (λ)∼-30 ppm of NFO, makes them suitable materials to evaluate as laminated magnetoelectric (ME) composites. A maximum ME response of 37, 67 and 86 mV/cm Oe at Hdc∼350−400 Oe field and 1 kHz frequency is observed for NKBT/NFO, NKBT/NFO/NKBT and NFO/NKBT/NFO layered composites, respectively. The high ME response at reasonable fields implies that NKBT/NFO laminated composite is a worthy lead-free candidate for ME sensor and energy harvesting applications. © 2020 Elsevier Ltd

Materials Today Communications

Magnetoelectric response in lead-free Na0.4K0.1Bi0.5TiO3/NiFe2O4 laminated composites

This study shows development of highly sensitive and stable localized surface plasmon resonance (LSPR)-active U-bent glass and polymeric optical fiber (GOF and POF) sensor probes by a seed-mediated in situ growth technique. Here, the nickel/nickel oxide seeds (Ni/NiO, 3 to 5&nbsp;nm size) were formed on the U-region of the fiber probe by sputter coating nickel under a low vacuum (3&nbsp;Pa), and then, gold nanostructures (AuNSs) were grown over the Ni/NiO seeds. The evanescent wave absorbance (EWA) phenomenon in the U-bent fiber probe was exploited to monitor the growth kinetics of AuNSs in real-time. Experimental observations point to a potential galvanic replacement of Ni by Au. The newly formed AuNSs on U-bent GOF and POF probes gave rise to a LSPR-based refractive index sensitivity of 27.66 and 25.65 ΔA/ΔRIU with plasmonic peak at 600 and 570&nbsp;nm, respectively. These plasmonic probes show an excellent chemical and mechanical stability, in addition to high surface&nbsp;enhanced Raman scattering (SERS) activity. This quick and facile technique is highly suitable for large-scale manufacture of reliable plasmonic fiber optic sensor probes for chemical and bio&nbsp;sensing applications.

Fulltext

Plasmonics

Highly Stable Plasmonic Nanostructures on a Nickel-Sputtered Glass and Polymeric Optical Fiber Sensors

This paper investigates the transitional flow dynamics behind a passively flapping airfoil supported by nonlinear springs in the presence of gusty inflow. The fluid-structure interaction (FSI) framework is composed of an incompressible Navier-Stokes solver weakly coupled with a two degree-of-freedom (dof) nonlinear structural model. The fluid-elastic system shows a rich bifurcation behavior in terms of successive Hopf bifurcations in uniform flow condition as the mean wind speed is increased. Presence of gusty fluctuations in the inflow makes the dynamics more complex through transitional states that we refer to as ‘intermittency’ between different dynamical states. A regular intermittent state between quasi-periodic dynamics and low amplitude aperiodic response has been observed when the FSI system is subjected to a time harmonic gust in terms of sinusoidal fluctuation. A parametric study has been carried out for various amplitudes and frequencies of the sinusoidal fluctuation to demarcate the transitional regimes. Thereafter, the system is subjected to random gusts modeled as Ornstein-Uhlenbeck process and ‘on-off’ and ‘burst’ type intermittent dynamics have been observed for long time-scale and short time-scale input fluctuations respectively. The intermittent states have been characterized through time series analyses tools and the corresponding flow-field dynamics has been investigated in detail. © 2021, Springer Nature Switzerland AG.

Department of Aerospace Engineering

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

Transitional Flow Dynamics Past a Passively Flapping Airfoil in Gusty Flow

Flow over airfoil is extensively studied to identify point of flow separation, transition, re-attachment (formation of laminar separation bubble), and to understand relation between aerodynamic forces generated by airfoil with change in angles of attack. Extension of flow separation concept to finite wing is not straight forward as flow has an additional degree of freedom to move when it detaches from surface of wing. A preliminary investigation of location of flow separation lines over finite wings is carried out using numerical simulations in ANSYS (FLUENT).

Lecture Notes in Mechanical Engineering

Investigation of Flow Separation Lines Over a Finite Wing

This study investigates the transitional wake dynamics of a simultaneously pitching-heaving airfoil in the low Reynolds number regime. The transition from Kármán to reverse Kármán wakes and the subsequent wake deflection are known to take place entirely in the periodic regime as the dynamic heave velocity (proportionally, the amplitude-based Strouhal number) is gradually increased. However, further increase in may result in the loss of dynamic stability of the deflected vortex street and an eventual transition to chaos. This phenomenon has largely remained unexplored in the existing literature. The present study attempts to fill this gap and aims to establish a dynamic link between the near-and far-field wake transitions. It is shown that the deflected jet undergoes a switching of deflection direction in the far-field as the near-field encounters a quasi-periodic transition with the increase in. The quasi-periodic behaviour of the near-field is seen to get interspersed with intermittent aperiodic windows, resulting in a complete reversal of the deflection direction through flipping of the immediate vortex couple. Eventually, the wake topology becomes fully chaotic through a series of rapid aperiodic jet-switching. To the best of the authors' knowledge, this is the first study that investigates the role of this aperiodic jet-switching in ushering in chaos in the wake of a pitch-heave flapping system. The mechanism of jet-switching and the role of leading-edge vortex are also revealed. Flow field dynamics during these changes and the underlying vortex interactions are analysed using nonlinear dynamical tools. © 2021 The Author(s). Published by Cambridge University Press.