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

A unique hybrid Aerodynamic Shape Optimization (ASO) framework is devised for axisymmetric bodies with minimum drag coefficient in hypersonic inviscid flow at zero angle of attack. The hybrid ASO framework that has been developed in this paper makes use of a combination of low fidelity framework and high fidelity framework, with the intention to reduce the turn-around time from initial guess to final optimal solution with accurate estimation of cost function. This was achieved when low fidelity framework was able to generate near optimal solution with quick and reasonably accurate estimation of coefficient of drag (cost function for present study). The near optimal solution was then fed as the initial guess for high fidelity framework and it accelerated the convergence to global optimal solution. The low fidelity framework comprised of Modified Newtonian Theory as flow solver while ANSYS FLUENT (v 14.5) formed the flow solver for high fidelity framework. Optimization was effected using Steepest Decent in both the framework and Bezier curves were used for generic shape representation of bodies. ICEM-CFD was used to create the structured grid as required in Fluent. The result show significant reduction in computational cost from initial guess to final optimal solution. It was also observed that the optimal solution obtained from proposed multi-fidelity framework and optimal solution from CFD simulation only, are nearly comparable with marginal difference in the volume. The optimization also resulted in a reduction of coefficient of drag by more than 28%. © Springer India 2017.

World University root node

Lecture Notes in Mechanical Engineering

A hybrid aerodynamic shape optimization approach for axisymmetric body in hypersonic flow

We propose an algorithm to solve thermobuoyant flows in the presence of magnetic field in enclosures with large temperature differences. The method is based on a staggered/non–staggered finite volume framework for incompressible flows which is modified to solve quasi-incompressible flows with heat transfer in the presence of applied magnetic field. The present framework is solves a single equation for normal momentum in the domain. This equation is discretized using a second–order convection scheme while central differencing is adopted for the viscous terms. An implicit solution approach which is first order accurate in time is employed and the resulting non–linear system of equations is 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 a collocated framework, with a first–order upwind 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 an ILU preconditioned GMRES solver using the LiS library. The approach is however still pressure–based with the energy equation employed to derive the divergence constraint to be used for solution of the pressure correction equation. Studies in enclosures over a range of temperature differences indicate that proposed approach can successfully simulate magneto-hydrodynamics convective flows with large density variation. © 2017, Begell House Inc. All Rights Reserved.

International Symposium on Advances in Computational Heat Transfer

Numerical investigation of high temperature gradient thermobuoyant flows with magnetic field

The study of dispersed laminar gas-particle flow in a horizontal channel is carried out using finite volume method on unstructured grid. In this context, Eulerian-Eulerian two-fluid model is employed to analyze the flow behaviour of both the phases inside the flow domain. The interaction between the gas phase and the particle phase is taken care by introducing the drag force term in their governing equations. The behavior of the particle phase when released at a low velocity into a uniform fluid flow is analyzed for particles having different sets of diameters. It has been found that for the particles of same material density, particle diameter plays an important role in the amount of drag force experienced by the particle phase dispersed in a continuous fluid medium. © Springer India 2017.

Eulerian-Eulerian modeling of dispersed laminar gas-particle flows over an unstructured grid

This paper proposes a vertical planar 2PRP-2PPR parallel manipulator along with a serial planar RRR passive orthosis (exoskeleton/supporting system) for performing sitting/lying type (stationary trainer) lower limb rehabilitation therapies in the sagittal plane. Proposed system's kinematic arrangement along with forward and inverse solutions is presented. System dynamics is derived to understand the behavior of the over-constrained manipulator-orthosis system. Further, a robust motion control scheme is proposed and the motion control scheme is based on non-singular fast terminal sliding mode control along with a nonlinear disturbance observer. The effectiveness and usefulness of the proposed manipulator is shown with the implementation of the motion controller through computer based numerical simulations using a clinical gait motion pattern. The proposed motion control scheme is also validated on an in-house fabricated prototype through motion control experiments. The controller parameter sensitivity and controller robustness are further analyzed at different working conditions. In comparison to the conventional controllers, the proposed control scheme possess few advantages namely better robustness, less chattering, high precision and fast finite time convergence, and can work in the presence of parameter uncertainties. From the demonstration, the proposed manipulator has certain advantages over existing stationary lower limb rehabilitation trainers namely, simple design, larger workspace, higher stiffness, modular design and low cost. © 2017 Elsevier Ltd

Mechanism and Machine Theory

Design, development and control of a 2PRP-2PPR planar parallel manipulator for lower limb rehabilitation therapies

A meshfree framework for numerical simulations of magnetohydrodynamic flows is proposed. The framework is based on the Least-Squares-Based Upwind Finite Difference method (LSFD-U) and is capable of handling arbitrary point distributions. The approach is based on the least-squares method of error minimisation to compute the inviscid flux derivatives. The flux derivatives at every point require the fluxes at the point as well as those in fictitious interfaces in a neighbourhood around it. The fluxes at the fictitious interfaces are computed by using any numerical flux formula of interest that incorporates upwinding and consequently a global rather than the one-sided stencil may be chosen for computation. The meshfree framework is implemented through AUSM scheme, using a first-order accurate spatial and temporal discretisation. Studies on the one-dimensional MHD shock tube problems demonstrate the efficacy of the algorithm. The effect of non-uniform point distributions on the performance of the meshfree framework particularly with regard to conservation has also been studied. On the non-uniform grid the solutions of meshfree framework are not in agreement with the solutions of the finite volume framework unlike on uniform meshes. The finite volume formulation is known to be conservative and therefore it is very clear that meshfree formulation has conservation issues particularly as the grid becomes more non-uniform. It is therefore desirable to have a formulation for meshfree framework that preserves conservation at a discrete level like the finite volume method. Attempts have been made to develop a conservative meshfree framework using weighted least-squares technique for a particular case of one-dimensional non-uniform point distribution. © Springer India 2017.

A meshfree framework for ideal magnetohydrodynamics

A pilot scale atomization setup is built to produce metal powder by atomizing molten tin from an annular free-fall nozzle, using high-speed nitrogen gas. The primary breakup mechanism of liquid tin is investigated using high-speed shadow imaging technique starting from the inception of the atomization process. Two different protrusions of the melt nozzle at different gas flow rates are investigated. The atomization process starts by the initiation of surface waves in varicose and sinuous modes of instability. The primary breakup of the molten liquid column is characterized by a series of bag breakup events in multiple directions and subsequent breakup of the rim. The primary breakup mechanism through bag breakup in a free-fall nozzle is very different from breakup mechanisms through "melt-sheet" formation and "umbrella breakup" reported earlier in the context of close-coupled nozzles. © 2017 by Begell House, Inc.

Atomization and Sprays

Study of primary breakup of molten tin during powder production in free-fall configuration

FEM simulation and single grit experimental techniques are available to get an insight into the chip formation mechanism in grinding operations. However, those are case specific. In the present work, an analytical method has been developed by considering specific energy criteria and Johnson's indentation theory to predict the modes of chip formation. The force acting on an abrasive grit at every instance in a trajectory path has been calculated by considering grit size, wheel size, kinematic conditions and work material properties. Yield coefficient and non-dimensional strain at the grit-work interaction have been computed to identify mainly the ploughing to cutting transition phase. © 2017 The Authors.

Fulltext

Procedia CIRP

An Analytical Method for Prediction of Material Deformation Behavior in Grinding Using Single Grit Analogy

The ability to estimate grinding process responses, like the surface roughness, specific energy, cutting forces and temperature, is essential to understand and optimize abrasive grinding. Several models to predict the process behavior with various input parameters have been published. In all of them, the number of active grits per unit area is an important parameter; however, this parameter has been given limited attention. Due to the difficulties associated with the accurate prediction and measurement of grits per unit area, very few grinding models have considered this factor, and most treat it as a constant. The active grits count depends on the depth of cut, the type of wheel, and the nature of the workpiece material. In contrast, the cutting edges count depends mainly on wheel-dressing conditions. A method has been developed to predict the active grits count by assuming a stochastic distribution of abrasive grits and their physical interaction with the workpiece based on a presumed abrasive wear mechanism. In addition, the count of active cutting edges has been included by using dressing kinematics. The variation in the number of active grits count with the depth of cut, grit size, dressing conditions and work material nature was used to validate the efficacy of this newly-proposed, predictive method. © 2017 Elsevier B.V.

Wear

A method for prediction of active grits count in surface grinding

We carry out a linear elastic analysis to study wavy structure generation on lipid membrane by peripheral membrane proteins. We model the lipid membrane as linearly elastic and anisotropic material. The hydrophobic insertion by proteins into the lipid membrane has been idealized as penetration of rigid rod-like inclusions into the membrane and the electrostatic interaction between protein and membrane has been modeled by a distributed surface traction acting on the membrane surface. With the proposed model we study curvature generation by several binding domains of peripheral membrane proteins containing BAR domains and amphipathic alpha-helices. It is observed that electrostatic interaction is essential for curvature generation by the BAR domains. © 2017 Federation of European Biochemical Societies

FEBS Letters

Generation of wavy structure on lipid membrane by peripheral proteins: a linear elastic analysis

Texturing the rake face of the cutting tools has recently emerged as a promising and environment friendly method for reducing friction during machining. Laser surface texturing has been the most commonly used method for fabricating textures on the cutting tool. This paper reports the experimental study of fabricating an array of micro scale dimples on the rake face of high speed steel cutting tool using a pulsed Nd:YAG laser. The effect of the laser parameters like wavelength and fluence on the dimensions and form of individual dimples were studied. Analysis of results show that uniform circular shaped dimples with very little spatter can be obtained using low fluence levels at wavelength of 355 nm. An array of micro scale dimples were then fabricated on the cutting tool using the optimized parameter levels. A very low textured area density was used in order to understand the process of chip flow over the textures and study the effect of machining on individual dimples. This textured cutting tool was then used in orthogonal dry machining of Al7075-T6 aerospace alloy and compared with the performance of conventional tools. Use of textured cutting tools resulted in reduction of both cutting and thrust forces. The tool-chip contact length is also less in the case of textured tool. The results show that textured high speed steel tools can significantly improve the metal cutting process while dry machining ductile workpieces. © 2017 Elsevier B.V.