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

Approximate multidimensional Riemann solvers are essential building blocks in designing globally constraint-preserving finite volume time domain and discontinuous Galerkin time domain schemes for computational electrodynamics (CED). In those schemes, we can achieve high-order temporal accuracy with the help of Runge–Kutta or ADER time-stepping. This paper presents the design of a multidimensional approximate generalized Riemann problem (GRP) solver for the first time. The multidimensional Riemann solver accepts as its inputs the four states surrounding an edge on a structured mesh, and its output consists of a resolved state and its associated fluxes. In contrast, the multidimensional GRP solver accepts as its inputs the four states and their gradients in all directions; its output consists of the resolved state and its corresponding fluxes and the gradients of the resolved state. The gradients can then be used to extend the solution in time. As a result, we achieve second-order temporal accuracy in a single step. In this work, the formulation is optimized for linear hyperbolic systems with stiff, linear source terms because such a formulation will find maximal use in CED. Our formulation produces an overall constraint-preserving time-stepping strategy based on the GRP that is provably L-stable in the presence of stiff source terms. We present several stringent test problems, showing that the multidimensional GRP solver for CED meets its design accuracy and performs stably with optimal time steps. The test problems include cases with high conductivity, showing that the beneficial L-stability is indeed realized in practical applications. © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.

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Journal of Scientific Computing

Multidimensional Generalized Riemann Problem Solver for Maxwell’s Equations

We present a comprehensive investigation of Partially-Saturated-Cells method (PSC) for the simulations of incompressible thermal flows. The methodology comprises an additional collision operator introduced into the conventional simplified thermal lattice-Boltzmann (STLBM) method that offers a unified evolution equation for solid and fluid media present in the computational domain. It is a type of diffuse-interface immersed-boundary method that is dictated by the volume fraction of the solid medium and facilitates a smooth transition of boundary conditions at the solid-fluid interface. In this work, we devise a mechanism to evaluate local heat flux at the solid-fluid interface and present its congruity with several heat transfer problems. We also derive the recovery of the macroscopic energy equation from PSC's evolution equation through Chapman-Enskog multiscale expansion. Our investigation also reveals that the method is first-order accurate for moving body simulations irrespective of the straight or curved boundary. It is also Galilean invariant and demonstrates identical heat transfer characteristics in stationary and moving reference frames. A comprehensive analysis of the PSC algorithm is presented to enlighten its suitability for predicting thermo-hydrodynamic characteristics in free, forced, and mixed convection phenomena involving both stationary and moving boundary scenarios. To the best of our knowledge, these aspects pertaining to PSC methodology have not been discussed in the literature so far. © 2023 Elsevier Ltd

International Journal of Heat and Mass Transfer

Comprehensive assessment of the partially-saturated-cells framework for convective problems

Aluminium matrix composites (AMCs) have found widespread applications in automobile, aerospace and marine industries because of their attractive properties. These include good strength to weight ratio, better corrosion and fatigue resistance. Stir casting has been identified as the most suitable method to fabricate AMCs because it provides good matrix-reinforcement bonding while also being a cost-effective process for mass production. However, this process suffers from drawbacks that include cast porosity, less wettability and agglomeration of reinforcement particles. A means to overcome these disadvantages is the use of acoustic cavitation using ultrasonic vibrations which can scatter the agglomerated particles and creates a uniform distribution of particles through acoustic streaming. Since the effect of ultrasonic cavitation is extremely localized, it is often combined with stir casting method to leverage the advantages of both approaches while negating their respective demerits. This hybrid approach known as Ultrasonic Assisted Stir Casting can be used to fabricate AMCs with better mechanical properties. The regions of cavitation as well as acoustic streaming in this process are strongly influenced by parameters such as power, wave frequency and container geometry which directly impact the performance characteristics of the process. In this work, we numerically investigate the influence of acoustic parameters and geometry of the processor container on cavitation regions and acoustic streaming. Simulation results showed that the cavitation region is concentrated near to the sonotrode and the acoustic streaming results in a circulating flow within the processor container.The analysis of cavitation zones and streaming patterns in these preliminary studies without reinforcement particles is expected to provide insights to optimize the acoustic parameters for uniform distribution of particles. © 2023 Author(s).

AIP Conference Proceedings

Numerical investigation of ultrasonic cavitation in stir cast aluminium matrix melt composites

In the present work, we investigate the accuracy and robustness of our in-house OpenMP parallelized direct-forcing immersed boundary–lattice Boltzmann (DF-IB-LB) solver by undertaking studies on accuracy, discrete conservation, Galilean invariance and quantification of spurious force oscillations (SFO). Our study reveals that DF-IB-LB exhibits first and second-order spatial accuracy for velocity and pressure errors, respectively, for generic moving boundary problems. The method is found to be Galilean invariant, while errors in discrete conservation and SFO decay linearly and superlinearly, respectively, with grid refinement. The numerical simulations with the proposed solver on a vast number of complex moving boundary problems involving imposed and induced motion highlight its efficacy as a fast, robust and accurate framework for single-phase flows with and without fluid–particle interactions. © 2022, The Author(s) under exclusive licence to OWZ.

Computational Particle Mechanics

Computational assessment of immersed boundary–lattice Boltzmann method for complex moving boundary problems

The least squares and Green-Gauss gradient schemes have been traditionally studied as two distinct techniques for gradient computation on unstructured meshes in the literature. In this Letter, we show that the Green-Gauss gradient method can be interpreted as a weighted least squares gradient scheme and that methods of the Green-Gauss family may therefore be encompassed in the larger set of least squares-based gradient schemes. © 2023 Author(s).

Physics of Fluids

A least squares perspective of Green-Gauss gradient schemes

We consider steady, fully-developed flows of deformable, inelastic grains driven by gravity between identical bumpy walls. Using constitutive relations from extended kinetic theory (EKT) for the erodible bed near the centreline and the collisional flow between the surfaces of the bed and the walls, we calculate the fields of mean velocity, fluctuation velocity and solid volume fraction across the chute. We consider both situations in which the solid volume fraction at and near the centreline is high enough to form a bed and when it is not. We compare results predicted by EKT with recent discrete element simulations results, and obtain very good agreement.

Journal of Fluid Mechanics

Extended kinetic theory for granular flow in a vertical chute

We investigate arbitrarily large indentations of beams in two dimensions by a frictionless and rigid cylindrical punch whose axis is perpendicular to the plane of the beam. The beam is modeled as a geometrically exact beam that admits large displacements and rotations. Absence of both friction and inter-penetration between the contacting surfaces allows the normal contact pressure and the separation between the surfaces to be related by the Karush–Kuhn–Tucker (KKT) conditions. This is then implemented in a nonlinear finite element framework through both penalty and augmented lagrangian methods. We solve for the contact domain and the forces and moments acting within it, and relate them to the total applied force and the extent of indentation. We report results for several punch radii and beam thicknesses and consider both pinned and clamped beams. In this, we discuss the importance of nonlinear effects such as wrapping of the beam around the punch and the stiffening of the beam due to axial stretch. We demonstrate the importance of utilizing a nonlinear beam formulation by comparing our results with the predictions of theories predicated on small deformations. For example, while the latter claim loss of contact with the beam in the vicinity of the punch’s apex as the indentation proceeds, we find that the punch and the beam remain in contact. &nbsp;

International Journal of Solids and Structures

Indentation of geometrically exact beams

Cellular membranes are highly dynamic in shape. They can rapidly and precisely regulate their shape to perform various cellular functions. The protein’s ability to sense membrane curvature is essential in various biological events such as cell signaling and membrane trafficking. As they are bound, these curvature-sensing proteins may also change the local membrane shape by one or more curvature driving mechanisms. Established curvature-sensing/driving mechanisms rely on proteins with specific structural features such as amphipathic helices and intrinsically curved shapes. However, the recent discovery and characterization of many proteins have shattered the protein structure–function paradigm, believing that the protein functions require a unique structural feature. Typically, such structure-independent functions are carried either entirely by intrinsically disordered proteins or hybrid proteins containing disordered regions and structured domains. It is becoming more apparent that disordered proteins and regions can be potent sensors/inducers of membrane curvatures. In this article, we outline the basic features of disordered proteins and regions, the motifs in such proteins that encode the function, mem- brane remodeling by disordered proteins and regions, and assays that may be employed to investigate curvature sensing and generation by ordered/disordered proteins.

Journal of Membrane Biology

Insights into Membrane Curvature Sensing and Membrane Remodeling by Intrinsically Disordered Proteins and Protein Regions

Haynes 282 is a creep-resistant, γ′ strengthened nickel-based superalloy with excellent weldability. Additive manufacturing, especially laser powder bed fusion (LPBF), of Haynes 282 is being researched for its potential applications in aerospace and power generation sectors. LPBF enables us to achieve desired properties via microstructure control through process parameter optimization. Integrated computational materials engineering (ICME) approach can be used to tune the process parameters to obtain desired microstructure, instead of trial-and-error methods. In this report, ICME framework has been established to simulate microstructural evolution during LPBF and post-processing of Haynes 282. A dimensionless number was used to optimize the process parameters with minimal porosity. Thermal modelling was performed using a semi-analytical model and the obtained thermal data was used to simulate solidification during LPBF. The corresponding cell spacing obtained matched closely with the experimental data. The segregation pattern extracted from the phase-field model was used as input for homogenization simulation. The γ′ precipitate evolution was predicted using Langer–Schwartz theory and Kampmann–Wagner-Numerical (KWN) approach. The predicted values agreed with the experimentally measured values. The room temperature yield strength of as-built samples was comparable and that of heat-treated samples were superior to the aged wrought material.

Journal of Materials Science

ICME framework to simulate microstructure evolution during laser powder bed fusion of Haynes 282 nickel-based superalloy

The title problem is 2-D exterior problem which is solved here by superposing Flamant problems followed by annihilating far-field and boundary tractions using limiting case of Lame’s problem. This method being identical to that used for classical problem of disk under diametral compression (corresponding interior problem), leads to closed-form solution for the exterior problem. Series solution is applicable for distributed loads, which in the limit approaches solution for the title problem. FEM which can model only finite geometries, approximates the infinite domain in the limit. The latter two methods are adopted here for validation of the analytical method by comparison. The analytical method is extended to solve three-point, four-point and n-point loading cases on the circular hole boundary.