Department of Mechanical Engineering

Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

World University root node

Cryogenics

Prediction of vapour-liquid and vapour-liquid-liquid equilibria of nitrogen-hydrocarbon mixtures used in JT refrigerators

We propose both monolithic and partitioned approach to solve conjugate heat transfer in an immersed boundary framework for complex geometries. The present framework is based on the staggered/non-staggered finite volume framework for incompressible flows which is extended to handle conjugate heat transfer. The key difference in the monolithic framework is that only a single hybrid momentum equation for normal momentum and single hybrid energy equation for temperature are solved simultaneously for both fluid and solid domains. However, in partitioned approach the energy equation is solved in each sub domain and temperature of both domains are coupled using suitable boundary conditions. The equations are discretized using a second-order accurate spatial and temporal scheme, that uses three point backward differencing for time discretisation and high-resolution schemes for convective discretisation, while central differencing is adopted for the viscous terms. The resulting discretized non-linear system of equations are solved using the Newton-Krylov approach. The momentum field at the cell centroids is then reconstructed using a defect-correction algorithm. The energy conservation equation is discretized similar to the collocated framework, with a second-order convection scheme for the convective terms and implicit Euler time stepping. These equations are linearized by considering the velocity field at the latest available time step, and the resulting linear system of equations are solved using SAAMG preconditioned GMRES solver using the LiS library. The effect of immersed solids are accounted for in the governing equation using a solid fraction approach. The investigations are be carried out for conjugate heat transfer with a backward-facing flow at different ratios of solid to fluid thermal diffusivities. Studies show that both monolithic and partitioned approaches can successfully simulate conjugate heat transfer with a backward-facing flow although the former shows a faster convergence to steady state solution. © 2018 by the authors of the abstracts.

International Conference on Computational Methods for Thermal Problems

A comparison between monolithic and partitioned approach for conjugate heat transfer in an immersed boundary framework

The objective of this present work is to study the effect of initial relative density (IRD) on microstructure evolution of sintered Al–4wt.%B4C preforms during hot compression tests with different temperatures and strain rates. The hot compression tests of sintered Al–4wt.%B4C preforms were performed in a hydraulic press for different range of temperature (300–500) °C, strain rate (0.1–0.3 s−1), IRD (80–90)%, and deformation degree (10–50)%. The microstructure of sintered Al–4wt.%B4C preforms was characterized by optical microscope, and the average dynamic recrystallization grain size was calculated by intercept line method. It is found that the average grain size of sintered Al–4wt.%B4C deformed preforms is increased with increasing deformation temperature and IRD, whereas it decreased with increasing the strain rate and deformation degree. On the other hand, the average grain size of sintered Al–4wt.%B4C deformed preforms is dependent on the Zener–Hollomon (Z) parameter. © 2018, Springer Science+Business Media, LLC, part of Springer Nature and ASM International.

Metallography, Microstructure, and Analysis

Analysis of Grain Size Evolution of Sintered Al–4wt.%B4C Preforms Subjected to Hot Compression

In this paper, a robust finite time trajectory tracking control approach is proposed for autonomous underwater vehicle (AUV), which belongs to the class of highly nonlinear, coupled dynamics with motion in 6-degrees-of-freedom (DOF). The finite-time error convergence and robust control task is accomplished by designing a non-singular fast fuzzy terminal sliding mode controller (NFFTSMC) with disturbance estimator for the 6-DOF dynamics of an AUV. The proposed NFFTSMC incorporates a non-singular fast terminal sliding mode controller (NFTSMC) which not only assures faster and finite convergence of the tracking errors to the equilibrium from anywhere in the phase portrait but also eliminates the issue of singularity dilemma appeared in conventional terminal sliding mode controller (TSMC); a fuzzy logic control (FLC) tool is employed to generate the hitting control signal in order to reduce chattering in control inputs, which commonly occur in conventional TSMC, and an estimated uncertainty term to compensate for the un-modeled dynamics, external disturbances, and time-varying parameters. Furthermore to investigate the effectiveness of the proposed method, it has been extended to task space control problem of an AUV - manipulator system (AUVMS) employed for underwater manipulation tasks. Simulation studies confirms the potency of the proposed method. © 2018 Elsevier Ltd

Ocean Engineering

Disturbance estimator based non-singular fast fuzzy terminal sliding mode control of an autonomous underwater vehicle

This study describes a computational framework for non-Oberbeck-Boussinesq buoyancy-driven turbulent convection coupled with thermal radiation at large temperature difference. A low-Mach number (LMN) model based on the Favre-averaged (Navier-Stokes and energy) equations with the standard k-ε model is presented using unstructured finite volume method. The proposed model is used to simulate turbulent buoyancy-driven convection influenced by radiative heat transfer in a differentially heated square cavity with large temperature and density variation. The primary emphasis of the present study is to understand the non-Oberbeck-Boussinesq effects on buoyancy driven turbulent convection-radiation interaction in enclosures and its influence on overall flow dynamics and heat transfer. In this context, simulations are performed at Rayleigh numbers Ra=109,1010 and 1011 for pure natural convection and coupled convection with surface and gas radiation (τ = 0.2 and 1) at a large temperature difference. Results for Ra=1010 are discussed extensively for all the scenarios. Studies on the influence of Rayleigh number are performed for a particular case of coupled convection with gas radiation (τ=0.2). These simulations reveal that the consideration of wall and gas radiation leads to asymmetry in the flow and heat transfer. Further, the convection currents intensify, and the magnitude and extent of the turbulence effects primarily increase with the consideration of thermal radiation in the simulation. Additionally, the deviations between the proposed variable density low-Mach number model and popularly used incompressible model based on Reynolds averaged governing equations are quantified. The deviation between the two models is found to be growing with the increase in the optical thickness which invalidates the commonly used Boussinesq approximation for such flows. © 2018

International Journal of Thermal Sciences

Investigations of turbulence-radiation interaction in non-Oberbeck-Boussinesq buoyancy-driven flows

The development of a non-Boussinesq flow solver for simulating combined radiative-convective heat transfer is presented on arbitrary polygonal meshes using the ideas of low-Mach number asymptotics. A segregated approach for solving the governing equations using a fractional step methodology on finite-volume method is adapted to handle the low-Mach number formulation. Simulations are carried out for two- and three-dimensional problems involving combined convective-radiative heat transfer both in the small and large temperature difference regimes. It is shown through investigations over a range of Gay-Lussac's and Planck numbers that non-Boussinesq effects could become significant due to the sole influence of large temperature difference and radiative heat transfer. Furthermore, the influence of non-Boussinesq effect on overall heat transfer is larger for the three-dimensional simulation of a given radiation-convection heat transfer problem relative to the two-dimensional assumption for the same problem. Interestingly, even at the low-temperature difference with the presence of significant radiation the Boussinesq approximation fails. This study clearly identifies the limits of validity of the Boussinesq approximation and conclusively prove that solutions to radiation-convection heat transfer problems are best acquired using a quasi-incompressible approach as described in this work. © 2018 Elsevier Ltd

International Journal of Heat and Mass Transfer

Unified framework for buoyancy induced radiative-convective flow and heat transfer on hybrid unstructured meshes

Micromachining techniques such as mechanical micro-drilling, electrical discharge machining (EDM) and laser beam machining (LBM) play an important role in the manufacturing of micro-devices used in mechanical, electronics, aerospace and medical applications. In this paper, an effort has been made to compare the performance of these micromachining techniques with regard to tool wear, burr formation and surface integrity. This is done by producing 20 micro-holes of approximately 800 μm diameter on a rectangular block (90×30×3 mm3) of Nimonic 80A superalloy. TiAlN coated WC micro-drills, Cu electrodes and CO2 laser beam are used to produce these holes in conventional micro-drilling, EDM and LBM, respectively. The quality of the drilled hole (diameter, surface roughness and micro-burr formation), tool diameter analysis, taper angle and material removal rate (MRR) are compared and reported. A comprehensive analysis is also carried out on overcut, which leads to hole inaccuracy. Results show that mechanical micro-drilling produces better results in the above mentioned characteristics in comparison to LBM and EDM techniques. The relatively better performance of mechanical micro-drilling is attributed to the usage of TiAlN coating on WC tool. © 2018, National Institute of Science Communication and Information Resources (NISCAIR). All rights reserved.

Indian Journal of Engineering and Materials Sciences

Performance evaluation of mechanical micro-drilling, electrical discharge machining and laser beam machining on nimonic 80A alloy

In this study, a robust nonlinear control method with an uncertainty estimator is proposed and applied to a kinematically redundant mobile manipulator (MM) position tracking in its task space. The proposed MM has four degrees-of-freedom (dof) serial manipulator mounted on three of mobile bases. The proposed method incorporates a feed-forward control term to reinforce the control action with extravagance from the desired acceleration vector; a disturbance estimator to reimburse for the unknown effects such as parametric uncertainties, external disturbances, unmodeled dynamics and a decentralized PID (proportional-integral-derivative) controller as a feedback loop to strengthen the stability of the system. The main strengths of the proposed scheme are its high robustness against parameter uncertainties and external disturbances, simplicity in design and ease of implementation. The effectiveness, feasibility, and robustness of the proposed method are illustrated using computer-based simulations with and without uncertainty estimator. © 2017 Elsevier Ltd

Computers and Electrical Engineering

Robust task-space motion control of a mobile manipulator using a nonlinear control with an uncertainty estimator

We present an interpolation-free diffuse interface immersed boundary method for multiphase flows with moving bodies. A single fluid formalism using the volume-of-fluid approach is adopted to handle multiple immiscible fluids which are distinguished using the volume fractions, while the rigid bodies are tracked using an analogous volume-of-solid approach that solves for the solid fractions. The solution to the fluid flow equations are carried out using a finite volume-immersed boundary method, with the latter based on a diffuse interface philosophy. In the present work, we assume that the solids are filled with a “virtual” fluid with density and viscosity equal to the largest among all fluids in the domain. The solids are assumed to be rigid and their motion is solved using Newton's second law of motion. The immersed boundary methodology constructs a modified momentum equation that reduces to the Navier–Stokes equations in the fully fluid region and recovers the no-slip boundary condition inside the solids. An implicit incremental fractional-step methodology in conjunction with a novel hybrid staggered/non-staggered approach is employed, wherein a single equation for normal momentum at the cell faces is solved everywhere in the domain, independent of the number of spatial dimensions. The scalars are all solved for at the cell centres, with the transport equations for solid and fluid volume fractions solved using a high-resolution scheme. The pressure is determined everywhere in the domain (including inside the solids) using a variable coefficient Poisson equation. The solution to momentum, pressure, solid and fluid volume fraction equations everywhere in the domain circumvents the issue of pressure and velocity interpolation, which is a source of spurious oscillations in sharp interface immersed boundary methods. A well-balanced algorithm with consistent mass/momentum transport ensures robust simulations of high density ratio flows with strong body forces. The proposed diffuse interface immersed boundary method is shown to be discretely mass-preserving while being temporally second-order accurate and exhibits nominal second-order accuracy in space. We examine the efficacy of the proposed approach through extensive numerical experiments involving one or more fluids and solids, that include two-particle sedimentation in homogeneous and stratified environment. The results from the numerical simulations show that the proposed methodology results in reduced spurious force oscillations in case of moving bodies while accurately resolving complex flow phenomena in multiphase flows with moving solids. These studies demonstrate that the proposed diffuse interface immersed boundary method, which could be related to a class of penalisation approaches, is a robust and promising alternative to computationally expensive conformal moving mesh algorithms as well as the class of sharp interface immersed boundary methods for multibody problems in multi-phase flows. © 2018 Elsevier Inc.

Journal of Computational Physics

Diffuse interface immersed boundary method for multi-fluid flows with arbitrarily moving rigid bodies

The present study considers a measure for enhancing mixing capability in micromixers. It incorporates a new design of obstacle, in the form of thin curved ribs, inside the micromixer and explored numerically for its mixing capabilities. The ribs can be uniquely defined by its chord length (l) and its thickness (to). An in-house three-dimensional finite volume solver based on quasi-incompressible formulation is employed for the simulations. Results show that the use of curved obstacles enhances mixing efficiency with a significantly lower pressure drop compared to that of using straight ribs. Also, a set of parametric studies is conducted for effects of parameters namely number of modules, angle of inclination, size and spacing between the curved obstacles and with inlet Re. The results show that mixing can be enhanced with the increase in the number of modules, sizes etc. of the obstacles. About 45 % mixing enhancement has been observed for the channel having curved obstacles with of four modules and 60 ∘ angle of inclination than that of no obstacle case. © 2017, Springer-Verlag GmbH Germany.