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

Background. The human hand plays a crucial role in accomplishing activities of daily living. The contribution of each finger in the human hand is remarkably unique in establishing object stabilization. According to the mechanical advantage hypothesis, the little finger tends to exert a greater normal force than the ring finger during a supination moment production task to stabilize the object. Similarly, during pronation, the index finger produces more normal force when compared with the middle finger. Hence, the central nervous system employs the peripheral fingers for torque generation to establish the equilibrium as they have a mechanical advantage of longer moment arms for normal force. In our study, we tested whether the mechanical advantage hypothesis is supported in a task in which the contribution of thumb was artificially reduced. We also computed the safety margin of the individual fingers and thumb. Methodology. Fifteen participants used five-finger prismatic precision grip to hold a custom-built handle with a vertical railing on the thumb side. A slider platform was placed on the railing such that the thumb sensor could move either up or down. There were two experimental conditions. In the "Fixed"condition, the slider was mechanically fixed, and hence the thumb sensor could not move. In the "Free"condition, the slider platform on which the thumb sensor was placed could freely move. In both conditions, the instruction was to grasp and hold the handle (and the platform) in static equilibrium. We recorded tangential and normal forces of all the fingers. Results. The distribution of fingertip forces and moments changed depending on whether the thumb platform was movable (or not). In the free condition, the drop in the tangential force of thumb was counteracted by an increase in the normal force of the ring and little finger. Critically, the normal forces of the ring and little finger were statistically equivalent. The safety margin of the index and middle finger did not show a significant drop in the free condition when compared to fixed condition. Conclusion. We conclude that our results does not support the mechanical advantage hypothesis at least for the specific mechanical task considered in our study. In the free condition, the normal force of little finger was comparable to the normal force of the ring finger. Also, the safety margin of the thumb and ring finger increased to prevent slipping of the thumb platform and to maintain the handle in static equilibrium during the free condition. However, the rise in the safety margin of the ring finger was not compensated by a drop in the safety margin of the index and middle finger. Copyright 2020 Rajakumar and SKM.

Department Of Chemistry

Fulltext

PeerJ

Comparable behaviour of ring and little fingers due to an artificial reduction in thumb contribution to hold objects

Resin Film Infusion (RFI) process is used for manufacturing large and thick unidirectional fiber reinforced polymer (UD FRP) composite structures for load bearing applications. Designing these load bearing structures requires the knowledge of effective elastic and strength characteristics of these composites. In this study, strength and stiffness properties of UD FRP manufactured through RFI process are predicted using a micromechanical modeling approach. A 3D representative volume element (3DRVE) with hexagonal array of fibers is used and all nine elastic constants of UD FRP composite are predicted. Failure models for fiber and resin are used to predict longitudinal tension/compression, transverse tension/compression and longitudinal shear strengths. Experiments were conducted on UD FRP composite manufactured through RFI process to obtain strength and stiffness properties. Results of experiment and simulations are compared and results validated.

Department of Engineering Design

World University root node

Materials Today: Proceedings

Characterization of unidirectional fiber reinforced polymer composites manufactured through resin film infusion process using micromechanical modeling

Magnetorheological (MR) gels belong to a group of smart materials whose attributes can be altered when it is exposed to an external magnetic field. In this paper, the investigation on the creep behavior of MR gels under constant stress is performed. MR gels are prepared by dispersing carbonyl iron (CI) microparticles of different volume percentages (10%, 20%, 30%) in a polymer gel. Using a free decay test apparatus built in-house, the effect of the magnetic field on the creep behavior of MR gels with various volume percentages of CI particles is studied, and the results are compared. From the results, a clear increasing trend is noticed in the creep resistance of the magnetic gel with the increase in the volume percentage of the particles under the same magnitudes of the magnetic field. The obtained experimental creep data are fitted suitably using a three-parameter model. © 2020, © 2020 Taylor & Francis Group, LLC.

Mechanics of Advanced Materials and Structures

Creep behavior of magnetorheological gels

Different body postures that can be maintained for a certain duration with awareness are called yogaasanas. These asanas matter flexibility, coordination, and strength, while the breathing practices and meditation sharpens the mind for better awareness and reduce anxiety and thus adds quality into life. Other beneficial effects might involve a reduction of stress, blood pressure, and improvements in resilience, mood, and metabolic regulation. The asanas performed regularly for a short duration in hours is well studied in the literature. However, when performed for a long duration continuously for several hours (40-hour yogathon), without food and sleep has a significant effect in regulating homeostasis. The homeostasis is accessed through cardio-respiratory and galvanic skin response changes. The study shows the physiological changes after the yogathon and compares it with effects on physiology due to short term yoga. It also emphasizes on the reduction of dependency on food, because of energy compensation through yoga-asanas. © 2021 by IGI Global. All rights reserved.

Handbook of Research on Evidence-Based Perspectives on the Psychophysiology of Yoga and Its Applications

An exploration of influence of duration on physiological effects of asanas

The primary aim of the research reported in this paper was to understand the effect of change of gusty simple shear inflow’s gradient on the force and moment patterns of a flapping wing in the 3D reference frame. A wing undergoing one degree of freedom asymmetric flapping and rectangular planform shape was considered. The gradient of the gusty simple shear inflow profile, Vgrad, was varied from –10 to +10 in steps of 5 and corresponding vertical and horizontal forces and moment about the flapping axis were computed. Time series of these forces and moment were used to plot the global recurrence plots and were compared. Quantitative analysis of the findings was carried out by the windowed recurrence quantification analysis of the force and moment patterns. Eight recurrence parameters, viz. recurrence rate, determinism, laminarity, trapping time, ratio, entropy, maximum line and trend were calculated and compared. Numerical investigations revealed that negative gusty shear gradient induced a considerable increase in vertical force and moment and marginally decreased the horizontal forces. Positive gusty shear gradient induced a marginal increase in horizontal forces but caused a substantial decrement in vertical force and moment. © 2020, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

On the Recurrence Signatures of Flapping Wings Exposed to Gusty Simple Shear Flow

For millimetre to micron sized bubbles, floating at the free surface of different low viscosity fluids with different surface tensions, and then collapsing, we study the ensuing expansion of the outer radius of the hole (ro) at the free surface, as well as its velocity of expansion (uo). Since the thin film cap of the bubble disintegrates before the hole in it reaches the static rim, the hole expansion at intermediate times occurs as if it initiates at the bubble's static rim of radius Rr; the evolution of ro then results to be a strong function of gravity, since Rr depends strongly on the bubble radius R. A scaling analysis, which includes the increase in the tip radius due to mass accumulation and the resulting change in the retraction force, along with the gravity effects by considering the hole radius in excess of its initial static radius, re = ro-Rr, results in a novel scaling law re/R∼(t/tc)4/7, where tc=ρR3/σ is the capillary time scale; this scaling law is shown to capture the evolution of the hole radii in the present study. The dimensionless velocities of hole expansion, namely, the Weber numbers of hole expansion, Weo=ρuo2R/σ, scale as Weo∼(t/tc)-6/7, independent of gravity effects, matching the observations. We also show that these Weber numbers, which reduce with time, begin with a constant initial Weber number of 64, while the viscous limit of the present phenomena occurs when the bubble Ohnesorge number Oh=μ/σρRâ‰ 0.24. © 2020 Author(s).

Physics of Fluids

Hole expansion from a bubble at a liquid surface

We study concentration-driven natural convection boundary layers on horizontal surfaces, subjected to a weak, surface normal, uniform blowing velocity Vi for three orders of range of the dimensionless blowing parameter 10-8 ≥ J = Re3x/Grx ≥ 10-5, where Rex and Grx are the local Reynolds and Grashof numbers at the horizontal location x, based respectively on Vi and ΔC, the concentration difference across the boundary layer. We formulate the integral boundary layer equations, with the assumption of no concentration drop within the species boundary layer, which is valid for weak blowing into the thin species boundary layers that occur at the high Schmidt number (Sc - 600) of concentration-driven convection. The equations are then numerically solved to show that the species boundary layer thickness δd = 1.6 x(Rex/Grx )1/4, the velocity boundary layer thickness δv = δdSc1/5, the horizontal velocity u = Vi(Grx/Rex )1/4f (n), where n = y/δv, and the drag coefficient based on Vi, CD = 2.32/vJ.We find that the vertical profile of the horizontally averaged dimensionless concentration across the boundary layer becomes, surprisingly, independent of the blowing and the species diffusion effects to follow aGr2/3y scaling, where Gry is the Grashof number based on the vertical location y within the boundary layer.We then show that the above profile matches the experimentally observed mean concentration profile within the boundary layers that form on the top surface of a membrane, when a weak flow is forced gravitationally from below the horizontal membrane that has brine above it and water below it. A similar match between the theoretical scaling of the species boundary layer thickness and its experimentally observed variation is also shown to occur. © The Author(s), 2020.

Journal of Fluid Mechanics

Scaling in concentration-driven convection boundary layers with transpiration

Heat transfer across fluid–solid interfaces in nanoconfinement has received significant attention due to its relevance in nanoscale systems. In this study, we investigate the Kapitza resistance at the water–graphene interface with the help of classical molecular dynamics simulation techniques in conjunction with our recently proposed equilibrium molecular dynamics (EMD) method [S. Alosious et al., J. Chem. Phys. 151, 194502 (2019)]. The size effect of the Kapitza resistance on different factors such as the number of graphene layers, the cross-sectional area, and the width of the water block was studied. The Kapitza resistance decreases slightly with an increase in the number of layers, while the influence of the cross-sectional area and the width of the water block is negligible. The variation in the Kapitza resistance as a function of the number of graphene layers is attributed to the large phonon mean free path along the graphene cross-plane. An optimum water–graphene system, which is independent of size effects, was selected, and the same was used to determine the Kapitza resistance using the predicted EMD method. The values obtained from both the EMD and the non-equilibrium molecular dynamics (NEMD) methods were compared for different potentials and water models, and the results are shown to be in good agreement. Our method allows us to compute the Kapitza resistance using EMD simulations, which obviates the need to create a large temperature gradient required for the NEMD method.<h4>ACKNOWLEDGMENTS</h4>

Department Of Chemical Engineering

Kapitza resistance at water–graphene interfaces

Electrokinetic flows are generally analyzed, assuming isothermal conditions even though such situations are hard to be achieved in practice. In this paper, the flow of a symmetric electrolyte in a charged nanochannel subjected to an axial temperature gradient is investigated using molecular dynamics simulations. We analyze the relative contribution of the Soret effect, the thermoelectric effect, and the double layer potential in the electrical double layer for various surface charges and temperature gradients. We find the flow driven by thermal gradient is analogous to electroosmotic flow. The thermophoretic motion of the electrolyte is significant for negative surface charge than the positive surface charge. The vibrational spectrum of graphene is calculated to delineate the effect of the surface charge polarity on the observed thermophoretic motion of the electrolyte. A unique structure of interfacial water layer is observed for the positive and negative surface charges. We attribute the presence of these structures to the differences in water-carbon interactions existing for various surface charge polarity. For an applied thermal gradient in the range 2.6 K nm-1 to 8 K nm-1, we observe a continuous net flow with average velocities reaching up to 9.4 m s-1 inside the channel for a negative surface charge of -0.101 C m-2. The results indicate that in a charged graphene-based nanochannel, temperature gradients can be employed to induce streaming current, depending on the relative influence of the Soret effect and the double layer potential. © 2020 IOP Publishing Ltd.

Department Of Civil Engineering

Nanotechnology

Non-isothermal flow of an electrolyte in a charged nanochannel

A heat pump unit using CO2 as working fluid is designed to meet not only a part of the heating demand in the centralised kitchen at The Akshaya Patra Foundation, Bengaluru, India, but also the entire cooling demand to replace the existing HCFC units for AC. The proposed heat pump system generates hot water at  90oC which is stored in hot water storage tanks for use in the cooking cauldrons. Moreover, the existing space cooling systems are replaced by a centralised cooling system which circulates chilled water. In order to handle the fluctuation in cold and hot water demand, thermal storage systems are proposed. This concept offers substantial reductions in GHG emissions from the cooling system (approximately 60%). Furthermore, for the overall system (cooking process and space cooling) the reduction in energy demand, energy cost and GHG emissions are all above 30%. © 2020 International Institute of Refrigeration. All rights reserved.