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

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.

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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

This paper uses a numerical post-stall predictive tool based on ‘decambering’ approach to study the aerodynamic characteristics of a lead-trail formation in pre and post-stall flow conditions. A basic lead-trail formation consisting of 2 wings and an extended formation consisting of 5 wings are studied with a view to the possibility of fuel savings, increase in range of operation, delayed flow separation and efficient positioning of the wings with respect to each other. Whether increasing the number of wings in a configuration is more useful is also looked into. The optimum operational angles of attack for maximum advantage in terms of fuel efficiency of all wings is studied including post-stall angles of attack. Numerical results for CL, CDi, section Cl distribution and their dependence on vertical offsets and angle of attack are reported. © 2019 Elsevier Masson SAS

European Journal of Mechanics, B/Fluids

Aerodynamic analysis of basic and extended lead-trail formation using numerical technique

Carbon capture and sequestration (CCS) is necessary to mitigate global warming caused by anthropogenic CO 2 emissions in the atmosphere. However, due to very high storage cost, it is difficult to sustain the CCS industry. The hot sedimentary and dry rock reservoirs with very high temperature can support both geothermal energy production, and carbon geosequestration economically, provided the CO 2 is used as a heat-carrying fluid with proper optimization of injection parameters according to reservoir conditions. In this paper we have reviewed past studies discussing the working mechanisms, pressure management strategies and various advantages of energy extraction from hydrothermal reservoirs by CO 2 plume geothermal technology and hot dry rock— enhanced geothermal system (EGS) technology. Past studies highlighted that due to very high thermal expansivity and mobility, supercritical CO 2 can produce more heat than water-EGS. For low enthalpy (around 50 ∘C) and shallow (0.5–1.5 km) reservoirs, CO 2 can fetch more heat than water because of higher heat capacity. Other advantages of CCS and EGS are (i) the production of brine or CO 2 assisting to manage the reservoir pressure and restrict the fluid interference with neighboring reservoirs, (ii) the fluid loss, which is a significant concern in a water-EGS but for CO 2-EGS it is environmentally friendly, and (iii) higher pressure and cold fluid injection induced geological deformation and microseismicity are relatively less for CO 2-EGS than water-EGS. In this paper, we have also discussed various challenges of CO 2-EGS to enable CCS in hydrothermal reservoir and hot dry rock system. © 2020, Springer Nature Switzerland AG.

GENERAL

Geomechanics and Geophysics for Geo-Energy and Geo-Resources

Potential of CO 2 based geothermal energy extraction from hot sedimentary and dry rock reservoirs, and enabling carbon geo-sequestration

Surfactant and polymer are used to improve oil recovery. The micro-emulsion phase composition, viscosity and interfacial tension vary with salinity and injection concentration of chemicals. The viscosity contrast which is very large for heavy oil reservoirs, results in various types of viscous instabilities. There is no comprehensive field-scale modelling on the viscous fingering affecting the oil recovery for different types of surfactant-polymer (SP) flooding. We numerically simulated the above phenomena for different types of SP flooding in five-spot wells setup for both water-wet and oil-wet reservoirs. We have observed that many saturation shocks and banks of micro-emulsion, water and polymer are formed. The viscous fingering at the interface of these banks depend on the reservoir wettability, micro-emulsion phase behaviour and injection concentration of chemicals. Fingering can be suppressed by changing the duration of injection and concentration of surfactant and polymer. We have shown that Type II(+) flooding produces more oil than Type II(−) and Type III. But the oil production by Type II(−) can be increased by adopting better injection strategies. We have made a quantitative comparison of output, i.e., oil recovery vs inputs such as injected mass of chemicals, injection duration and pumping energy, which is of interest to industry. The pumping energy requirement is higher for Type II(−) flooding irrespective of wettability. Our results show that short duration injection of surfactant with multistep reduction of polymer concentration suppresses viscous instabilities and produce more than 90% OOIP. © 2019, Springer Nature Switzerland AG.

Numerical analysis of viscous fingering and oil recovery by surfactant and polymer flooding in five-spot setup for water and oil-wet reservoirs

We study the expansion of a vortex ring generated due to the spreading of ethanol-water droplets, with ethanol concentration range of 20%≤Ce ≤ 100%, on the surface of a 50-mm-deep water layer. Once deposited on the water layer, the surface tension difference leads to some part of the lighter ethanol droplet spreading as a thin film over the water layer. We observe an expanding vortex ring below the radially spreading film front. We visualize the film spreading from top using aluminum particles, while the vortex is visualized from the side using polyamide particles with laser induced fluorescence (LIF) from the dyed drop used to distinguish the alcohol from the water. Particle image velocimetry (PIV) is used to obtain the velocity and the vorticity fields below the spreading film. Vortex regions and their centers, identified by the λ2 method from the velocity fields, are tracked to determine the vortex expansion. We show that the vortex ring expands with the same velocity of expansion as that of the spreading ethanol film at the free surface, possibly since the vortex ring is created due to the surface tension difference across the film front. Using dimensional arguments, we also propose a scaling for the upward velocity,uΓ, induced by this expanding vortex ring and show that uΓ ∼ t−1/2. © 2020 by Begell House, Inc.

Journal of Flow Visualization and Image Processing

Vortex ring below a spreading alcohol film on water

Fluid flow and heat transfer characteristics past four elliptic cylinders arranged in square configuration are numerically investigated in this study. An in-house finite element method code based on streamline upwind Petrov - Galerkin algorithm has been used for simulations of two-dimensional, incompressible and laminar flow of air. Analyses are carried out by changing geometric parameters such as spacing ratio, axis ratio and incident angle. Results in terms of vorticity and temperature contours, Strouhal number, drag and lift coefficients and Nusselt number are studied for all cases. These results show that fluid flow patterns are strongly influenced by geometric parameters, based on which flow can be categorized into different types. A critical spacing ratio is found for some of the configurations, where a steep increase in drag coefficient is encountered. From this study, it is observed that incident angle 22.5 degree gives a higher heat transfer rate compared to the other two configurations (0 and 45 degree). Also, elliptic cylinders (axis ratio of 0.8 and 0.5) have similar Nusselt number value with less drag force compared to circular cylinders (axis ratio of 1.0) which justifies the utilization of elliptic cylinders as an alternative for circular ones. © 2020 Taylor &amp; Francis Group, LLC.

Department of Mechanical Engineering

Heat Transfer Engineering

Effect of Cylinder Arrangement on Fluid Flow and Heat Transfer Characteristics past Four Elliptic Cylinders

A two-dimensional numerical simulation of tandem wings flapping in inclined stroke plane kinematics is carried out. The distance between the two wings is varied to understand its effect on the vortex dynamics and dipole jet. Immersed boundary method is employed for the study. The change in instantaneous and average vertical force production of individual wings of the tandem wing configuration is compared to the single isolated wing. Further, various lift enhancement mechanism in the class of flows is understood. The alignment of dipole jet identified could be used in understanding the vertical force production of multiple flapping wings. © 2020, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

AIAA Scitech 2020 Forum

Numerical investigation of flapping wings in inclined stroke plane kinematics

In this, study, an attempt is made to differentiate muscle nonfatigue and fatigue condition using signal complexity metrics derived from phase space network features. A total of 55 healthy adult volunteers performed dynamic contraction of the biceps brachii muscle. The first and last curl are segmented and are considered as nonfatigue and fatigue condition respectively. A weighted phase space network is constructed and reduced to a binary network based on various radii. The mean and median degree centrality features are extracted from these networks and are used for classification. The results of the classification indicate that these features are capable of differentiating nonfatigue and fatigue condition with 91% accuracy. This method of analysis can be extended to applications such as diagnosis of neuromuscular disorder where fatigue is a symptom. © 2020 European Federation for Medical Informatics (EFMI) and IOS Press.

Studies in Health Technology and Informatics

Classification of biceps brachii muscle fatigue condition using phase space network features

In this paper, the development of a modified beamforming method, named as, Filtered Delay Weight Multiply and Sum (F-DwMAS) beamforming is reported. The developed F-DwMAS method was investigated on a minimum-redundancy synthetic aperture technique, called as 2 Receive Synthetic Aperture Focussing Technique (2R-SAFT), which uses one element in the transmit and two consecutive elements in the receive, for achieving high-quality imaging in low complex ultrasound systems. Notably, in F-DwMAS, an additional aperture window function is designed and incorporated to the recently introduced F-DMAS method. The different methods of F-DwMAS, F-DMAS and Delay and Sum (DAS) were compared in terms of Lateral Resolution (LR), Axial Resolution (AR), Contrast Ratio (CR) and contrast-to-noise ratio (CNR) in a simulation study. Results show that the proposed F-DwMAS resulted in improvements of LR by 22.86 % and 25.19 %, AR by 5.18 % and 11.06 % and CR by 152 % and 112.8 % compared to those obtained using F-DMAS and DAS, respectively. However, CNR of F-DwMAS was 12.3 % less compared to DAS, but 103.09 % more than F-DMAS. Hence, it can be concluded that the image quality improved by F-DwMAS compared to DAS and F-DMAS. © 2020 IEEE.