Department of Mechanical Engineering

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

Wettability patterning of a surface is a passive method to manipulate the flow and heat transport mechanism in many physical processes and industrial applications. This paper proposes a rational wettability pattern comprised of multiple superhydrophilic wedges on a superhydrophobic background, which can continuously remove the impacted spray droplets from the horizontal surface. We observed that the spray droplets falling on the superhydrophilic wedge region spread and form a thin liquid film, which is passively transported away from the surface. However, most of the droplets falling on the superhydrophobic region move towards the wedge without any flooding. The physics of the passive transport of the liquid film on a wedge is also delved into using numerical modelling. In particular, we elucidate the different modes of droplet transport in the superhydrophobic region and the interaction of multiple droplets. The observed droplet dynamics could have profound implications in spray cooling systems and passive removal of liquid from a horizontal surface. This study’s findings will be beneficial for the optimization of efficient wettability patterned surfaces for spray cooling application. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

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Processes

Droplet dynamics on a wettability patterned surface during spray impact

We conceptualize Distributed Learning Machines (DLMs) – a novel machine learning approach that integrates existing machine learning algorithms with traditional mesh-based numerical methods for solving forward and inverse problems in nonlinear partial differential equations (PDEs). In conventional numerical methods such as finite element method (FEM), the discretization of the computational domain is a standard technique to reduce the representation load of basis functions. Along the same lines, we propose a distributed neural network architecture that facilitates the simultaneous deployment of several localized neural networks to solve PDEs in a unified manner. The most critical requirement of the DLMs is the synchronization of the distributed neural networks. For this, we introduce a new physics-based interface regularization term to the cost function of the existing learning machines like the Physics Informed Neural Network (PINN) and the Physics Informed Extreme Learning Machine (PIELM). To evaluate the efficacy of this approach, we develop three distinct variants of DLM namely, time-marching Distributed PIELM (DPIELM), Distributed PINN (DPINN) and time-marching DPINN. We show that ideas of linearization and time-marching allow DPIELM to be able to solve nonlinear PDEs to some extent. Next, we show that DPINNs have potential advantages over existing PINNs to solve the inverse problems in heterogeneous media. Finally, we propose a rapid, time-marching version of DPINN which leverages the ideas of transfer learning to accelerate the training. Collectively, this framework leads towards the promise of hybrid Neural Network-FVM or Neural Network-FEM schemes in the future. © 2020 Elsevier B.V.

Neurocomputing

Distributed learning machines for solving forward and inverse problems in partial differential equations

A three-dimensional numerical investigation of airflow through heated fin-tube heat exchangers with winglet type vortex generators is performed for both inline and staggered arrangements of circular tubes. Heat transfer augmentation of such heat exchangers strongly depends on the mounting locations of the winglet pair corresponding to tubes. The present numerical study shows the effect of location of rectangular winglet pairs (RWPs) on thermal performance for both the arrangements. Among numerous considered RWP locations, all promising locations of RWPs are identified which give higher heat transfer enhancement with less flow loss. The effects of RWP locations on flow features and heat transfer are demonstrated by streamlines and Nusselt number contours respectively. Estimation of enhancement in heat transfer is achieved by Colburn's factor and flow loss is quantified from the measured pressure drop. The thermohydraulic effect is analyzed by using the thermal performance factor. Locations of RWPs, which are capable of producing higher thermal performance, have been optimized and found that upstream RWP location, i.e. ΔX = 2.0, ΔY = ±1.25 delivers higher heat transfer enhancement with maximum thermal performance factor value for both arrangements. Evaluation of secondary flow induced by RWPs is achieved by secondary flow intensity and is correlated with heat transfer. © 2020 Elsevier Ltd

Thermal Science and Engineering Progress

Numerical investigations on fluid flow and heat transfer characteristics of different locations of winglets mounted in fin-tube heat exchangers

An efficient synthesis of substituted 3,4-dihydroisoquinolinones through [4+2]-annulation ofN-chlorobenzamides/acrylamides having a monodentate directing group with alkylidenecyclopropanes in the presence of a less expensive, highly abundant and air stable Co(iii) catalystviaa C-H activation is demonstrated. In this reaction, the N-Cl bond ofN-chlorobenzamide serves as an internal oxidant and thus an external metal oxidant is avoided. The 3,4-dihydroisoquinolinone derivatives are converted successfully into the highly useful imidoyl chloride derivatives. The deuterium labeling and kinetic isolabelling studies reveal that the C-H activation is a rate-determining step in this cyclization reaction. © The Royal Society of Chemistry 2021.

Department Of Chemistry

Chemical Communications

Cobalt(iii)-catalyzed redox-neutral [4+2]-annulation ofN-chlorobenzamides/acrylamides with alkylidenecyclopropanes at room temperature

Semi-active systems using magnetorheological fluids have been realized in many novel devices such as linear dampers, rotary dampers, brakes, and so on. Rotary vane-type magnetorheological damper is one such device that uses magnetorheological fluid as a hydraulic medium and a controllable magnetorheological valve to generate variable resistance. This device, due to its limited angle motion, lends itself to a natural application for prosthetic knee joint. In this article, a bypass rotary vane-type magnetorheological damper suitable for prosthetic knee device is designed. In the proposed design, the rotary vane chamber and the bypass magnetorheological valve are connected using hydraulic cables and ports. The design of rotary cylinder is implemented based on the largest possible dimensions within the envelope of a healthy human knee, while the magnetorheological valve is designed optimally using a multi-objective genetic algorithm optimization. Off-state braking torque, induced on-state braking torque and mass of the valve are selected as three objectives. The torque and angular velocity requirements of the normal human knee are used as design limits. The optimal solution is chosen from the obtained Pareto fronts by prioritizing the objective of weight reduction of magnetorheological valve. The optimal solution is capable of producing a damping torque of 73 Nm at a design speed of 8.4 rpm and current supply of 1.9 A. Potential benefits offered by this design when compared with multi-plate magnetorheological brake are flow mode operation, large clearance gap, and fewer design components, thus reducing the manufacturing complexity. © The Author(s) 2020.

Journal of Intelligent Material Systems and Structures

Design of bypass rotary vane magnetorheological damper for prosthetic knee application

Alpha-tocopherol, a highly active form of the antioxidant vitamin E in humans, effectively scavenges free radicals and protects the cell membranes. The aim of our study was to enhance alpha-tocopherol production in sunflower cell suspension using elicitation, precursor addition and culture condition optimization. Among various elicitors and precursors studied, sodium chloride (50 mg/L) added as elicitor and phytol (50 mg/L) added as the precursor to an untransformed sunflower cell suspension, resulted in maximum productivity enhancement of alpha-tocopherol up to 2.3- and 1.9-fold, respectively compared to a control untransformed sunflower cell suspension (0.02 mg/L/d). In separate experiments, the volumetric productivity of alpha-tocopherol in the untransformed suspension was enhanced up to 2.1- fold (0.09 mg/L/d) under optimized conditions of light intensity (3500 lx), temperature (30 °C), initial pH (6.5) and inoculum size (6 g/L). We then extrapolated these strategies (elicitor and precursor addition, culture condition optimization) for implementation on a high alpha-tocopherol yielding metabolically engineered cell suspension overexpressing 4-hydroxyphenylpyruvate dioxygenase (TS4), which resulted in enhancement (1.9-, 1.45- and 2.72-fold respectively) in the volumetric productivity of alpha-tocopherol compared to the transformed cell suspension grown under control conditions (0.18 mg/L/d). Thus, integration of bioprocess optimization and metabolic engineering resulted in a multi-fold (up to 12-fold) enhancement in alpha-tocopherol productivity in comparison to the untransformed cells. Therefore, our study demonstrates that productivity enhancement strategies like bioprocess optimisation and metabolic engineering (developed separately in parallel) for a given system can be combined to achieve maximum productivity in lesser time and cost than a relay system of optimization in long-duration plant cell cultivations. © 2021, Society for Plant Biochemistry and Biotechnology.

Department Of Biotechnology

Journal of Plant Biochemistry and Biotechnology

Multi-fold enhancement in vitamin E (alpha-tocopherol) production via integration of bioprocess optimisation and metabolic engineering in cell suspension of sunflower

The flow stress reduction during plastic deformation superposed with electric current, commonly referred as 'electroplasticity' has been actively researched over the past few decades. While the existence of an electron-dislocation interaction, independent of Joule heating is established, the exact rate controlling mechanism of the observed behaviour lacks consensus. Understanding the governing mechanism is complex due to the combined effect of Joule heating and electron-dislocation interaction. The present work attempts to establish the electroplastic mechanism in AA 6063 alloy and its nanocomposites. The role of microstructure on the electron interaction is investigated by preparing four distinct microstructure from the base alloy. All the samples were subjected to constant amplitude direct current during plastic deformation. The Joule heating effect is decoupled using the experimentally measured temperature history. The potential electroplastic mechanism for the alloy is elucidated by analysing the trend of flow stress reduction with strain and strain rate. It is inferred that micro Joule heating and electron wind effect cannot completely explain the observed electroplastic behaviour in AA 6063. The SiC particles in nano-composites suppressed the electroplastic effect. The observed mechanical behaviour under electric current is in agreement with the trend predicted assuming magnetic depinning mechanism. The reduction of dislocation density quantified using X-ray diffraction is found to concur with the inferred mechanism. © 2021 The Author(s).

Department of Metallurgical and Materials Engineering

Journal of Materials Research and Technology

Microstructure dependent electroplastic effect in AA 6063 alloy and its nanocomposites

The influence of temperature on the tribological performance of alloy 718 is studied in the present work. The alloy 718 samples were used in double aged condition for reciprocating wear test with a ball on flat configurations. The wear tests were conducted at two conditions viz: room temperature and 300 °C temperature. The testing temperature had a significant influence on the coefficient of friction (COF) and wear resistance of alloy 718. The alloy 718 sample, subjected to high-temperature testing environment had a lower COF and higher wear rate compared to samples tested at ambient temperature. The lower COF values of the alloy 718 samples subjected to high wear testing temperature conditions were attributed to the extent and presence of glaze layer formation, which is insignificant in the case of samples subjected to ambient temperature. The higher wear rate values of the alloy 718 samples subjected to high wear testing temperature conditions were attributed to the due to occurrence of tribo-chemical reactions at the contact zone of tribo-pair. © 2021, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Investigation on Elevated Temperature Tribological Performance of Alloy 718

Labyrinth seals are the most widely used non-contact-type turbine seals. The main design concern is to prevent the seal rub with the stator in the range of operating conditions and to control the system rotordynamics. This work aims at experimentally evaluating the effect of thermal growth of labyrinth seal on the leakage flow rates and effect on vibration characteristics of the system. An experimental seal test rig for teeth on rotor (TOR)-type straight labyrinth seal with four flat tip teeth has been developed. Constant clearance between seal and stator is maintained and tested at different speeds and temperatures by varying the inlet air pressure. Leakage results are compared for the seal for the range of operating conditions and for a given seal radial clearance. In addition, vibration data are measured at various locations to understand the influence of seal on the vibration characteristics of the rotor system. It is seen that flow leakage rate and vibration of system are influenced by the pressure difference and the temperature. © 2021, Springer Nature Singapore Pte Ltd.

Experimental Study of Temperature Effect on Labyrinth Seal Leakage and Vibration Characteristics of Rotor

Lung cancer is a prominent type of cancer, which leads to high mortality rate worldwide. The major lung cancers lung adenocarcinoma (LUAD) and lung squamous carcinoma (LUSC) occur mainly due to somatic driver mutations in proteins and screening of such mutations is often cost and time intensive. Hence, in the present study, we systematically analyzed the preferred residues, residues pairs and motifs of 4172 disease prone sites in 195 proteins and compared with 4137 neutral sites. We observed that the motifs LG, QF and TST are preferred in disease prone sites whereas GK, KA and ISL are predominant in neutral sites. In addition, Gly, Asp, Glu, Gln and Trp are preferred in disease prone sites whereas, Ile, Val, Lys, Asn and Phe are preferred in neutral sites. Further, utilizing deep neural networks, we have developed a method for predicting disease prone sites with amino acid sequence based features such as physicochemical properties, conservation scores, secondary structure and di and tri-peptide motifs. The model is able to predict the disease prone sites at an accuracy of 81 % with sensitivity, specificity and AUC of 82 %, 78 % and 0.91, respectively, on 10-fold cross-validation. When the model was tested with a set of 417 disease-causing and 413 neutral sites, we obtained an accuracy and AUC of 80 % and 0.89, respectively. We suggest that our method can serve as an effective method to identify the disease causing and neutral sites in lung cancer. We have developed a web server CanProSite for identifying the disease prone sites and it is freely available at-https://web.iitm.ac.in/bioinfo2/CanProSite/. © 2020 Elsevier B.V.