Department of Mechanical Engineering

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IIT Jodhpur

The research paradigm for biosensing devices has been focussed to explore flexible sensors. Here, the term “flexible” is indicative of the substrate which has sufficient degree of deformability so that it could be suitably placed at any place. Advances in flexible sensing technologies can be observed by the number of smart products in the market as well as with the number of publications exponentially coming out every year in which diversified development in terms of device operation and performance have been explored. However, as is the case for most new developments, there are several challenges and opportunities which this relatively newfangled field is facing, both in the basic and applied aspects. These challenges and opportunities basically lie in three broad areas, namely design, fabrication, and integration of the developed flexible systems to improve the purpose-oriented sensing capabilities, such as sensing characteristics, functionality, so and so forth. In this chapter, fundamental aspect of various sensing films and associated mechanism has been illustrated. With this article, state-of-the-art work on the promising flexible sensing platforms for biomedical applications is also discussed. © 2018, Springer Nature Singapore Pte Ltd.

World University root node

Energy, Environment, and Sustainability

Flexible Sensors for Biomedical Application

We present a combined experimental and numerical study of an idealized model of the propulsive stroke of the turning manoeuvre in fish. Specifically, we use the framework of Lagrangian coherent structures (LCSs) to describe the kinematics of the flow that results from a thin plate performing a large angle rotation about its tip in still fluid. Temporally and spatially well-resolved velocity fields are obtained using a two-dimensional, incompressible finite-volume solver, and are validated by comparisons with experimentally measured velocity fields and alternate numerical simulations. We then implement the recently proposed variational theory of LCSs to extract the hyperbolic and elliptic LCSs in the numerically generated velocity fields. Detailed LCS analysis is performed for a plate motion profile described by during and zero otherwise. The stopping time is given by , the value of chosen to give a stopping angle of , resulting in a Reynolds number , where is the plate chord length and the kinematic viscosity of water. The flow comprises a starting and a stopping vortex, resulting in a pair of oppositely signed vortices of unequal strengths that move away from the plate in a direction closely aligned with the final plate orientation at . The hyperbolic LCSs are shown to encompass the fluid material that is advected away from the plate for t-{o}$]]>, henceforth referred to as the advected bulk. The starting and stopping vortices, identified using elliptic LCSs and hence more objective than Eulerian vortex detection methods, constitute only around two thirds of the advected bulk area. The advected bulk is traced back to to identify five distinct lobes of fluid that eventually form the advected bulk, and hence map the long-term fate of various regions in the fluid at . The five different lobes of fluid are then shown to be delineated by repelling LCS boundaries at . The linear momentum of the advected bulk region is shown to account for approximately half of the total impulse experienced by the plate in the direction of its final orientation, thus establishing its dynamical significance. We provide direct experimental evidence for the kinematic relevance of hyperbolic and elliptic LCSs using novel dye visualization experiments, and also show that attracting hyperbolic LCSs provide objective characterization of the spiral structures often observed in vortical flows. We conclude by showing that qualitatively similar LCSs persist for several other plate motion profiles and stopping angles as well. © 2018 Cambridge University Press.

Journal of Fluid Mechanics

The kinematic genesis of vortex formation due to finite rotation of a plate in still fluid

We report an experimental study of evaporation of two configurations of layered porous media that are heated from above by infrared (IR) radiation having ~1,000 W/m2 intensity. We used nearly monodisperse glass beads in each of the layers. The two configurations are (1) coarse and fine beads, stacked side by side and (2) fine beads over coarse beads (FoC). The IR heater mimics the natural evaporation process in soils, and the aim is to study, using three diagnostic tools, how the layering affects the evaporation process, and compare it with the homogeneous porous medium case. For each experiment we use three diagnostics simultaneously, evaporation rate measurement using a precision balance, surface temperature imaging using an IR camera, and visualization of the evaporation process with fluorescein dye. The constant (evaporation) rate period (CRP) regime, found in homogeneous porous media, is drastically changed for the two layered configurations. We show new results for side-by-side configuration. In the FoC configuration we show that the near-surface water content in the finer particles does not change in CRP and a true constant evaporation rate is possible. The average water depth at end of CRP in the porous medium, for a wide range of diameter ratios for the FoC configuration are compared with the predictions from theoretical relations proposed by Shokri et al. (2010, https://doi.org/10.1029/2009JB006743) and Assouline et al. (2014, https://doi.org/10.1002/2013WR014489). Using a simple surface energy budget, we show that knowing the surface temperature, the evaporation rate can be estimated with reasonable accuracy (±5%) during drying of a porous medium. ©2018. American Geophysical Union. All Rights Reserved.

Water Resources Research

Evaporation From Layered Porous Medium in the Presence of Infrared Heating

We know that on the global scale till now the major sources of energy are fossil fuels like coal, oil, and natural gases. Because of following three reasons, it is pertinent to use the naturally available renewable energy in the form of solar energy to replace fossil fuel energy: (a) With the advent of science and technology and with ever increasing global population, the total energy consumption is increasing day by day, (b) the fossil fuel reserves world over are fast depleting, and (c) the fossil fuels emit greenhouse gas during combustion, contributing significantly to global warming. Not surprising, during the last two, three decades, hectic research has been going on in almost all developed/developing countries to develop techniques to make maximum use of solar energy through various processes like thermal processes, photovoltaic processes. In India many research groups are actively engaged in studying utilization of solar energy in an efficient way using variety of techniques. The present monograph titled “Applications of Solar Energy” is the result of collection of work done by some such research groups. © 2018, Springer Nature Singapore Pte Ltd.

Introduction to Applications of Solar Energy

Solar power generation has accelerated worldwide during the last decade. Often the regions of high intensity of solar radiation are in the desert areas which are prone to Haboobs (Arabic word meaning "wind"). Haboobs are sandstorms caused by strong horizontal winds. They occur regularly in arid regions throughout the world. Impact of these events has been examined from various angles such as health, aviation, transportation, agriculture as they affect a billion people around the world. Here it is shown that these events can decrease the yield of a solar photovoltaic plant significantly. Analysis of measured solar radiation during a sand storm is carried out to assess its impact on solar power generation. © 2018 Author(s).

AIP Conference Proceedings

Can a sand storm in Arabia cause a dip in the yield of your photovoltaic plant?

Studies of drying from a conventional porous medium (CPM), consisting of spheres, have shown the existence of three periods. In the first period drying rate is high and essentially depends on the atmospheric demand while in the last stage mass transfer happens from within the porous medium and is solely governed by the internal properties. In a previous study (Kumar and Arakeri) it was shown, using a cluster of closely packed smooth rods stacked vertically, that stage 1 was sustained till nearly the whole liquid gets evaporated. Near-zero radii contacts, between the rods, offering infinite height rise was shown to be the reason behind such high sustained evaporation rates and elongated duration of stage 1. Here we show that the orientation of the rods dramatically changes the evaporation process from this vertically oriented rod-based porous medium (VRBPM). Unlike the vertical case, in the horizontal case (HRBPM) smooth rods do not support stage 1. In this case transition to stage 2 was due to the liquid-vapour meniscus receding continuously in the network from the start of the experiment. Rough rods pinned the liquid along its rough surfaces and stage 1 is sustained although its duration is much smaller compared to the vertical case. Maintained hydraulic connections against gravity along the roughness of the rods thus provides a better insight towards understanding stage 1 in a conventional porous medium consisting of complicated pore geometry and their connectivity. In all the experiments, infra-red heating at about 1000 W/m2 causes evaporation from an initially saturated RBPM kept in an acrylic box. © 2018 Elsevier Ltd

International Journal of Multiphase Flow

Experimental investigation of effect of orientation and surface roughness on drying of porous media consisting of rods

Studies of drying from a conventional porous medium, consisting of spheres, have shown the existence of three periods. In the first period evaporation rate is high and essentially depends on the atmospheric demand. Relatively simpler geometry, such as polygonal capillaries, pins liquid along the corner and retains high evaporation rate till a certain extent. We report an experimental study of evaporation from a new, but yet, simpler rod-based porous medium (RBPM) consisting of closely packed vertical circular rods. This configuration can be thought of an ‘extreme case’ of a polygonal capillary where the internal angle is zero (00). Infrared heating at about 1000 W/m2 causes evaporation from an initially saturated RBPM kept in an acrylic box. We find sustained high evaporation rates until almost all the water is depleted, a feature very different from either a conventional porous medium or a polygonal capillary. Near-zero radii contacts between the rods are able to source the liquid, against gravity, to the open end throughout the rod length (75 mm) and thus capillary depinning in all the experiments were forced due to limited liquid content. Using a novel fluorescein dye visualization technique and a simple mathematical model, we show that the corner films present in the near-zero radii contacts between rods results in the high sustained evaporation rate. © 2018 Elsevier Masson SAS

International Journal of Thermal Sciences

Sustained high evaporation rates from porous media consisting of packed circular rods

The effect of all-inclusive generic offset payload characteristics on the modes of vibration and nonlinear characteristics of a rotating flexible manipulator with a revolute pair has been accomplished in the present article. A brief dynamic modelling and free vibration analysis to obtain the eigenspectrums of the system, whereafter nonlinear analysis of a manipulator with a general offset payload undergoing overall motion has been accomplished. Dynamic equation of motion and associated boundary conditions have been developed where the payload is considered as a mass whose center of gravity doesn’t coincide with the point of attachment with the manipulator. The effect of various system parameters such as offset mass, offset inertia, offset length, hub mass, actuated inertia and hub stiffness on eigenfrequency is well tabulated and the same effect on eigenspectrums is presented graphically. Further, MMS is employed to investigate the effect of parametric variation on the nonlinear behaviour and associated bifurcation of the rotating single-link flexible manipulator being harmonically driven at the joint under primary resonance considering the centrifugal forces acting on the link and payload as well. The present analysis indicated the pronounced effect of system mass, inertia, stiffness and rotating speed on the eigencharacteristics and bifurcations of a flexible manipulator with a rotating joint. Copyright © 2018 ASME.

ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE)

Modal identification and nonlinear vibration of flexible manipulator with revolute pair incorporating generic payload

In creep-strength-enhanced ferritic steels, hydrogen-induced cold cracking of weldments is a serious issue. In the present research work, the effect of cooling medium on tensile properties and microstructure evolution of P91 steel weldments has been studied. For water-cooling condition, the diffusible hydrogen metal in deposited metal was measured by the mercury method. The microstructure of weldments in different cooling condition was characterized by using the field-emission scanning electron microscope (FE-SEM) and optical microscope. The fractured tensile test samples were characterized using the FE-SEM. The maximum tensile strength was measured to be 624 MPa for air-cooling medium (very low level of diffusible hydrogen). © 2018 Sociedade Portuguesa de Materiais (SPM)

Science and Technology of Materials

Effect of cooling medium on microstructure evolution and tensile properties of creep-strength-enhanced ferritic steel

The paper deals with the measurement of the residual stresses in P91 welded pipe using the blind hole drilling technique. The P91 pipe weld joints were prepared using gas tungsten arc welding process. The residual stress measurement was carried out using the strain gauge rosette that was associated with the plastic deformation of material and stress concentration effect of multi-point cutting tool. Strain gauge response was estimated experimentally using the tensile testing for the uniaxial loading while finite element analysis was performed for biaxial loading. Gas tungsten arc welds joint was prepared for conventional V-groove and narrow groove design. The corrective formulation was developed for calculating the corrected value of residual stresses from the experimentally obtained strain value. The corrected and experimental induced residual stresses values as per ASTM E837-13 were calculated for both V-groove and narrow groove design. Post weld heat treatment (PWHT) of P91 welded pipe was also conducted to study their effect on residual stresses. © 2018 Politechnika Wrocławska