Showing papers by "Kodakkal Kannan Viswanathan published in 2016"

Phase transition kinetics and surface binding states of methylammonium lead iodide perovskite.

Abstract: We have presented a detailed analysis of the phase transition kinetics and binding energy states of solution processed methylammonium lead iodide (MAPbI3) thin films prepared at ambient conditions and annealed at different elevated temperatures. It is the processing temperature and environmental conditions that predominantly control the crystal structure and surface morphology of MAPbI3 thin films. The structural transformation from tetragonal to cubic occurs at 60 °C with a 30 minute annealing time while the 10 minute annealed films posses a tetragonal crystal structure. The transformed phase is greatly intact even at the higher annealing temperature of 150 °C and after a time of 2 hours. The charge transfer interaction between the Pb 4f and I 3d oxidation states is quantified using XPS.

Free vibration of anti-symmetric angle-ply cylindrical shell walls using first-order shear deformation theory

Abstract: In the present study, free vibration of anti-symmetric angle-ply cylindrical shell walls is investigated under first-order shear deformation theory using the spline method. Assuming the displacement components in a separable form, a system of coupled equations on three displacement and two rotational functions are obtained. A generalized eigenvalue problem is obtained using the collocation procedure and applying the spline function approximation for displacement and rotational function. The resulting eigenvalue problem is solved for the frequency parameters to get as many eigenvalues as required starting from the least. The eigenvectors are the spline coefficients from which the mode shapes can be constructed. The parametric study showed the effect of length parameter, circumferential node number, ply angles, number of lay-ups, lamination materials and different boundary conditions on the shell frequency.

Growth mechanisms and origin of localized surface plasmon resonance coupled exciton effects in Cu2−xS thin films

Abstract: We have demonstrated a robust protocol to prepare Cu2−xS thin films with a controlled crystal phase and size which exhibit localized surface plasmon resonance (LSPR) coupled exciton effects by a simple template free single step wet chemical method without any surfactant. The LSPR frequency can be tuned in the Cu2−xS thin films by the growth temperature and time which controls the free carrier density. These selectively grown Cu2−xS thin films possess a tunable band gap (2.6–1.4 eV) due to the quantum size effect. The origin of the LSPR coupled exciton effects are discussed.

Free vibration of layered cylindrical shells filled with fluid

Abstract: The vibration of the layered cylindrical shells filled with a quiescent, incompressible, and inviscid fluid is analyzed. The governing equations of the cylindrical shells are derived by Love’s approximation. The solutions of the displacement functions are assumed in a separable form to obtain a system of coupled differential equations in terms of the displacement functions. The displacement functions are approximated by Bickley-type splines. A generalized eigenvalue problem is obtained and solved numerically for the frequency parameter and an associated eigenvector of the spline coefficients. Two layered shells with three different types of materials under clamped-clamped (C-C) and simply supported (S-S) boundary conditions are considered. The variations of the frequency parameter with respect to the relative layer thickness, the length-to-radius ratio, the length-to-thickness ratio, and the circumferential node number are analyzed.

Free vibration analysis of composite cylindrical shells with non-uniform thickness walls

Abstract: The paper proposes to characterize the free vibration behaviour of non-uniform cylindrical shells using spline approximation under first order shear deformation theory. The system of coupled differential equations in terms of displacement and rotational functions are obtained. These functions are approximated by cubic splines. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector which are spline coefficients. Four and two layered cylindrical shells consisting of two different lamination materials and plies comprising of same as well as different materials under two different boundary conditions are analyzed. The effect of length parameter, circumferential node number, material properties, ply orientation, number of lay ups, and coefficients of thickness variations on the frequency parameter is investigated.

Free Vibration of Cross-Ply Laminated Plates with Variable Thickness Based on Shear Deformation Theory

Abstract: Free vibration of laminated cross-ply plates of variable thickness including transverse problem is solved numerically to obtain eigenvalues as frequency parameter and associated eigenvectors which are spline coefficients. The variation of frequency parameters with respect to the aspect ratio, side-to-thickness ratio, ply-angle, number of layer and thickness variations for two different materials under simply supported boundary conditions are analyzed.

Numerical solutions of free convective flow from a vertical cone with mass transfer under the influence of chemical reaction and heat generation/absorption in the presence of UWT/UWC

Abstract: The purpose of this paper is to present a mathematical model for the combined effects of chemical reaction and heat generation/absorption on unsteady laminar free convective flow with heat and mass transfer over an incompressible viscous fluid past a vertical permeable cone with uniform wall temperature and concentration (UWT/UWC).The dimensionless governing boundary layer equations of the flow that are transient, coupled and non-linear partial differential equations are solved by an efficient, accurate and unconditionally stable finite difference scheme of Crank-Nicholson type. The velocity, temperature, and concentration profiles have been studied for various parameters viz., chemical reaction parameter , the heat generation and absorption parameter  , Schmidt number Sc , Prandtl number Pr , buoyancy ratio parameter N . The local as well as average skin friction, Nusselt number, Sherwood number, are discussed and analyzed graphically. The present results are compared with available results in open literature and are found to be in excellent agreement

Vibration of antisymmetric angle-ply laminated plates under higher order shear theory

Abstract: This paper deals with the analysis of vibration of antisymmetric angle-ply plates using spline method for higher order shear theory. Free vibration of laminated plates is addressed to show the capability of the present method in the vicinity of higher order shear deformation theory and simply supported edges of plates. The coupled differential equations are obtained in terms displacement and rotational functions. These displacement and rotational functions are approximated using cubic and quantic spline. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The antisymmetric angle-ply fiber orientation are taken as design variables. Numerical results enable us to examine the frequencies for various geometric and material parameters and accuracy and effectiveness of the proposed method is also verified by comparative study.

Vibration analysis of a shear deformed anti-symmetric angle-ply conical shells with varying sinusoidal thickness

Abstract: The study is to investigate the free vibration of antisymmetric angle-ply conical shells having non-uniform sinusoidal thickness variation. The arbitrarily varying thickness is considered in the axial direction of the shell. The vibrational behavior of shear deformable conical shells is analyzed for three different support conditions. The coupled differential equations in terms displacement and rotational functions are obtained. These displacement and rotational functions are invariantly approximated using cubic spline. A generalized eigenvalue problem is obtained and solved numerically for an eigenfrequency parameter and an associated eigenvector of spline coefficients. The vibration characteristic of the shells is examined for cone angle, aspect ratio, sinusoidal thickness variation, layer number, stacking sequence, and boundary conditions.

Exact solutions and lattice Boltzmann method modelling for shallow water equations

Abstract: In this study, lattice Boltzmann Method (LBM) is applied for shallow water flows problem in order to handle two dimensional flows. The LBM and its implementation in solving Shallow Water Equation (SWE)for physically significant nonlinear partial differential equations were also analysed.An analytical solution of steady and two dimensional SWE was derived from a cubic algebraic form of SWE, and obtained the analytical solution of unsteady and two-dimensional SWE from sub inertial and super inertial frequency quadratic algebraic form of SWE. The numerical solution of the two dimensional SWE was generated by applying the LBM. The LBM numerical result of SWE was then compared graphically with the SWE result obtained via the finite difference method (FDM). Our findings revealed that the simulation via LBM is more stable than FDM in the microscopic sense. AMS subject classification:

Free Vibration Study of Anti-Symmetric Angle-Ply Laminated Plates under Clamped Boundary Conditions

Abstract: Abstract Two type of numerical approach namely, Radial Basis Function and Spline approximation, used to analyse the free vibration of anti-symmetric angle-ply laminated plates under clamped boundary conditions. The equations of motion are derived using YNS theory under first order shear deformation. By assuming the solution in separable form, coupled differential equations obtained in term of mid-plane displacement and rotational functions. The coupled differential is then approximated using Spline function and radial basis function to obtain the generalize eigenvalue problem and parametric studies are made to investigate the effect of aspect ratio, length-to-thickness ratio, number of layers, fibre orientation and material properties with respect to the frequency parameter. Some results are compared with the existing literature and other new results are given in tables and graphs.

Free vibration of laminated truncated conical shell structure using spline approximation

Abstract: Free vibration of laminated truncated conical shell structures is studied by using spline approximation method. The governing equations of motion for conical shell are formulated in terms of longitudinal, circumferential and transverse displacement components, by using extension of Love’s first approximation theory. Assuming the displacement components are in a separable form, a system of coupled equations on three displacement functions for each shell are obtained. Since exact solutions are generally impossible, a numerical solution procedure is adopted in which the displacement functions are approximated by using Bickley-type splines of suitable order, which are cubic and quintic, resulting into a generalised eigenvalue problem. 1Corresponding author, E-mail: visu20@yahoo.com The convergence and comparative results are presented. Effects of the circumferential node number, relative thickness ratio, length ratio and semi-cone angle on the frequencies of the laminated truncated conical shell with two kinds of material properties under two different boundary conditions are investigated. AMS subject classification:

Elastic and seismic model for the generation of tsunamis via lattice Boltzmann method

Abstract: An efficient implementation of the Lattice Boltzmann method (LBM) for the numerical simulation of the generation tsunamis, based on Elastic wave equation and P-wave equation is presented. It is provided two examples where the scheme is used to model mechanisms for the generation of seismic waves. Numerical results show good agreement with the theory.

Modeling of propagation tsunami waves via lattice Boltzmann method

Abstract: We present an efficient implementation of the Lattice Boltzmann method (LBM) for the numerical simulation of the propagation of long ocean waves (e.g., tsunamis), based on the Nonlinear Shallow Water (NSW) wave equation. The Lattice Boltzmann Equation (LBE) method is an alternative numerical scheme for the description of incompressible hydrodynamics. The LBE method has potential to serve as an efficient solver for incompressible flows in complex geometries. In the present study, we propose nonlinear shallow water equations for irrotational surface waves for the case of complex bottom elevation. Nowadays shallow water equations have become the model of choice for operational tsunami modeling including the propagation zone estimation. Several test-cases are presented to highlight the added value of the new model. Some implications to tsunami wave modeling are also discussed. The numerical results are found to be in excellent agreement with theory.

Effects on MHD Flow of Oldroyd-B Fluid in a Porous Space via G-Jitter Combined with Heat and Mass Transfer

Abstract: The effects of stimulated g-jitter which come together with heat and mass transfer by mixed convection in microgravity situation on MHD flow of Oldroyd - B fluid in porous space is investigated for a particular system. The system comprises of a pair of heated up perpendicular parallel infinite plates maintained at constant although various concentrations and temperatures. By using modified Darcy’s law, the equations governing the flow are modelled. These equations are solved exactly for the distributions of stimulated velocity, temperature and concentration. Interestingly the solutions for second grade and Maxwell fluids are recovered as new limiting cases of the present general results. Similar result in the relevant literature relating to Newtonian fluid is also obtained as a special case of the present solution. Finally particular attention is given to the graphical results for the velocity profiles of the oscillating flow in the channel. The analysis on the variations of embedded flow parameters in the solution expressions are presented and discussed.

Comparative study of free vibration of anti-symmetric angle-ply laminated plates

Abstract: In this study free vibrations of anti-symmetric angle-ply composite plates including shear deformation under clamped-clamped boundary conditions are presented. Two types of numerical methods are adopted to analyze the problem. The spline and radial basis functions base mesh free scheme are applied simultaneously to approximate the displacement and rotational functions. Comparative studies have been made for analyzing the frequency parameters with respect to the material properties, number of layers, fiber orientations, side-to-thickness ratio and aspect ratio. The results are depicted in terms of tables and graphs.