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

The most hazardous kind of vehicle crash among all road accidents is vehicle rollover. Present-day rollover prevention systems in commercial vehicles mitigate rollover by preventing any wheel lift-off from the ground. These systems make use of actuators such as differential brakes and demand all the wheels on the ground for satisfactory operation. Such systems are not effective in recovering a vehicle from intense rollover scenarios where the wheels on one side are lifted off the ground, and the vehicle is about to rollover to the other side after reaching the tip-over point. A few studies have investigated the possibility of reinstating a vehicle at the tip-over point with the wheels on a side lifted off. The high complexity and computation time of the optimal control strategies such as nonlinear model predictive controller make it unsuitable for real-time implementations. This study proposes a novel gain-scheduled State-dependent Riccati Equation–based optimal anti-rollover controller for reinstating a vehicle from the tip-over point. An inverted double pendulum on a cart vehicle model is used as the plant model. The anti-rollover controller is found to be presentable as a two-dimensional gain-scheduled lookup table with specific state dependencies in existence. It eliminates the necessity of solving the nonlinear performance index minimization problem online. State-dependent Riccati Equation method adequately accounts for the nonlinearities involved, yet possesses a small computational time per sample. The anti-rollover controller is evaluated with a 10 degrees of freedom full vehicle model with a nonlinear pure slip tyre model that incorporates the dynamical effects neglected in the controller formulation. Finally, the anti-rollover controller is evaluated in real-life initial conditions using a sophisticated pick-up truck model obtained from TruckSim® software through a co-simulation with the anti-rollover controller setup in MATLAB®/Simulink® environment. The State-dependent Riccati Equation controller was found to be effective in reinstating the higher-order models from the tip-over point in all the case studies conducted. © IMechE 2020.

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Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering

Vehicle tip-over prevention using gain-scheduled State-dependent Riccati Equation–based anti-rollover controller

Context: Numerous minor bodies of our solar system are covered by loosely bound dust particles; these layers are called regolith. Light scattered by regolith surfaces is a function of their bulk porosity, of the sizes, shapes, structures and compositions of the constituent particles. Aims: To increase our data base, the present work is an extension of our previous work by Kar et al. (2016), where we reported light scattering data for regolith surfaces with different porosities, sizes, and composition of the particles (from very low to moderate absorption). The new samples have larger particles with moderate to high absorption, three originate from industry, and three are natural (among them a mixture of two previously studied samples). Methods: The samples were prepared with different bulk porosities. Photometric phase curves were built for two different geometrical configurations. The light source was a He–Ne laser at 632.8 nm. The phase angle (g) covered for the first configuration is from 45 to 126° and for the second configuration it is from 45 to 108°, in steps of 9 and 4.5° respectively. We maintained incident angle (i)= emergent angle (e) for the first configuration and i=45°, while e varying for the second configuration. The experimental data were fitted successfully to the semi-empirical model proposed by Hapke (2008) and interpreted in terms of the porosities and sizes of the particles. The albedo values obtained from the model for two samples are compared to those calculated directly from Mie theory. Results: The successful fit by the model is confirmed just as the increase of reflectivity with the decrease of porosities for a given composition and particle size. Further, it was observed that reflectivity increases with the decrease in particle size for a given composition. Finally, we have tested that for corundum and silicon carbide samples with a 22μm and 15μm particle sizes ( respectively), the best fitted albedo (ω) values that can be obtained from Hapke model, match very well with those calculated directly by Mie Theory. This also re-validated our approach adopted in the present work. © 2020 Elsevier Inc.

Icarus

Laboratory photometry of regolith analogues: Effect of porosity-II

Background and Aim: The proposed work was planned to evaluate the potential protective role of aqueous Aloe vera (AV) concentrate and/or Omega-3 fatty acids (O3FAs) against GM -initiated renal toxicity in rats. Materials and Methods: Thirty female Wistar-albino rats were distributed into five equivalent groups as follows: Normal control group, GM control group, GM + AV group (200 mg/kg, p.o.), GM + O3FAs group (100 mg/kg, p.o.), GM + AV + O3FAs group. All the treatments were administered for 10 days. Renal toxicity was initiated by intraperitoneal administration of GM (80 mg/kg/day) for last 5 days of test duration. Results: Noticeable rise in the levels of serum creatinine, urea, MDA, TNF-α, TGF-β1, Fibronectin and NGAL was seen alongside a significant decrese in the levels of serum albumin, total protein content and antioxidant enzymes, SOD, GSH, catalase in GM control group. Treatment with AV or O3FAs or AV + O3FAs exhibited a considerable reduction in serum creatinine, urea, MDA, TNF-α, TGF-β1, Fibronectin and NGAL levels and a rise in the levels of serum albumin, total protein and antioxidant enzymes. Conclusion: The study concluded the importance of AV and Omgea-3 fatty acids as effective nephroprotective agents. However, the combined treatment with AV and O3FAs showed similar beneficial effects as compared to monotherapy in mitigating adverse effects of GM-initiated renal toxicity. There was no significant difference observed in monotherapy as well as combination therapy. © 2021, Association of Pharmaceutical Teachers of India. All rights reserved.

Indian Journal of Pharmaceutical Education and Research

Therapeutic interventions using monotherapy versus combination therapy of aloe Vera and omega-3 fatty acids on gentamicin-initiated renal toxicity via attenuation of renal biomarkers

Inhomogeneous co-flowing fluids inside a microchannel exposed to an acoustic standing wave can lead to the relocation of the fluids. Here we investigate the use of combined acoustic relocation and acoustophoretic migration for the transfer of particles between co-flowing fluids inside a microchannel exposed to a standing pressure half-wave with a pressure nodal plane along the channel center line and antinodal planes along the walls. We show that under the influence of the applied field, particles suspended in a carrier fluid of low acoustic impedance flowing along the channel center are initially dragged toward the walls along with the relocating fluid and later migrate into the target fluid that relocates from the walls to the channel center. We found that the particle motion is initially controlled by the dominant fluid relocation-induced Stokes drag force and later governed by the primary acoustic radiation force as stable fluid configuration is reached. Experimentally we unraveled that depending on the operating parameters-particle size, flow rates, and acoustic energy density-the final locations of the particles at the end of the channel leads to three distinct regimes-complete medium exchange, partial medium exchange, and no medium exchange. Our study reveals that the relocation and migration dynamics of the particles is underpinned by the relevant timescales â advection timescale, acoustophoretic timescale, and the relocation timescale, which in turn govern the different regimes observed. Numerical simulations predicted the complete migration and nonmigration of particles of two different sizes, in agreement with the experimental observations. We also demonstrate the medium exchange and size-based sorting of biological cells, which shows the potential application of the study in biochemical assays. © 2021 American Physical Society.

Physical Review Fluids

Combined acoustic relocation and acoustophoretic migration for particle transfer between co-flowing fluids in a microchannel

In the present study rotating vaneless diffusers are considered to minimize energy losses associated with diffusion and to improve the operating range of the compressor. Depending on the speed of rotation the diffusers are classified into two types forced and free. Simulations using ANSYS CFX 17.2 are performed with free rotating diffusers, in which diffusers are rotated at fraction of impeller speed. The performance of rotating diffuser with the stationary diffuser is compared using several performance characteristics such as total pressure ratio, static pressure recovery coefficient, coefficient of torque and stagnation pressure loss coefficient are plotted in each case. Simulations are performed at different speed ratio over a range of 0.25-0.95. Among all the cases vaneless diffuser with speed ratio 0.75 has optimum performance in terms of performance characteristics and velocity streamlines are uniform with lower Mach number compared to the stationary vaneless diffuser. © 2021 Author(s).

AIP Conference Proceedings

Computational study of influence by rotating vaneless diffuser on the performance of centrifugal compressor

Numerical simulations using ANSYS Fluent 17.2 are carried out to explore the heat transfer characteristics of jet impingement on a protruded leading edge of a gas turbine blade. Many researchers have found that inclusion of protrusion does not improve Nusselt number though this contributes to augmentation in heat transfer due to an increase of surface area. In certain cases, the protrusion has also been found to degrade the heat transfer performance. Therefore, this work focuses on the effect of single protrusion to determine the effect of position of the protrusion on a concave surface and finally obtaining an optimized position of protrusions. The position of the single protrusion is varied at several angles with respect to the centre of the plate to explore the corresponding heat transfer characteristics. Thereafter, multiple protrusions are considered at desired positions to determine optimum effective location of protrusions for maximum heat transfer. The optimal position is determined using Genetic Algorithm. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Optimization of Protrusions for an Impinging Jet on a Curved Surface

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

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

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.

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.