A note on two upwind strategies for RBF-based grid-free schemes to solve steady convection-diffusion equations
In this paper, two radial basis function (RBF)-based local grid-free upwind schemes have been discussed for convection-diffusion equations. The schemes have been validated over some convection-diffusion problems with sharp boundary layers. It is found that one of the upwind schemes realizes the boundary layers more accurately than the rest. Comparisons with the analytical solutions demonstrate that the local RBF grid-free upwind schemes based on the exact velocity direction are stable and produce accurate results on domains discretized even with scattered distribution of nodal points. Copyright © 2009 John Wiley & Sons, Ltd.
On optimization of the RBF shape parameter in a grid-free local scheme for convection dominated problems over non-uniform centers
Global optimization techniques exist in the literature for finding the optimal shape parameter of the infinitely smooth radial basis functions (RBF) if they are used to solve partial differential equations. However these global collocation methods, applied directly, suffer from severe ill-conditioning when the number of centers is large. To circumvent this, we have used a local optimization algorithm, in the optimization of the RBF shape parameter which is then used to develop a grid-free local (LRBF) scheme for solving convection-diffusion equations. The developed algorithm is based on the re-construction of the forcing term of the governing partial differential equation over the centers in a local support domain. The variable (optimal) shape parameter in this process is obtained by minimizing the local Cost function at each center (node) of the computational domain. It has been observed that for convection dominated problems, the local optimization scheme over uniform centers has produced oscillatory solutions, therefore, in this work the local optimization algorithm has been experimented over Chebyshev and non-uniform distribution of the centers. The numerical experiments presented in this work have shown that the LRBF scheme with the local optimization produced accurate and stable solutions over the non-uniform points even for convection dominant convection-diffusion equations. © 2013 Elsevier Inc.
Free vibration study of anti-symmetric angle-ply laminated plates under clamped boundary conditions
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.
Upwind biased local RBF scheme with PDE centres for the steady convection diffusion equations with continuous and discontinuous boundary conditions
RBF based grid-free scheme with PDE centres is experimented in this work for solving Convection-Diffusion Equations (CDE), a simplified model of the Navier-Stokes equations. For convection dominated problems, very few integration schemes can give converged solutions for the entire range of diffusivity wherein sharp layers are expected in the solutions and accurate computation of these layers is a big challenge for most of the numerical schemes. Radial Basis Function (RBF) based Local Hermitian Interpolation (LHI) with PDE centres is one such integration scheme which has some built in upwind effect and hence may be a good solver for the convection dominated problems. In the present work, to get convergent solutions consistently for small diffusion parameters, an explicit upwinding is also introduced in to the RBF based scheme with PDE centres, which was initially used to solve some time dependent problems in [10]. RBF based numerical schemes are one type of grid free numerical schemes based on the radial distances and hence very easy to use in high dimensional problems. In this work, the RBF scheme, with different upwind biasing, is used to a variety of steady benchmark problems with continuous and discontinuous boundary data and validated against the corresponding exact solutions. Comparisons of the solutions of the convective dominant benchmark problems show that the upwind biasing either in source centres or PDE centres gives convergent solutions consistently and is stable without any oscillations especially for problems with discontinuities in the boundary conditions. It is observed that the accuracy of the solutions is better than the solutions of other standard integration schemes particularly when the computations are carried out with fewer centers.
Upwind strategies for local RBF scheme to solve convection dominated problems
The most common strategy existing in the literature for solving convection dominated Convection-Diffusion Equations (CDE) is using central approximation to the diffusive terms and upwind approximation to the convective terms. In the present work, we propose a multiquadric local RBF based grid-free upwind (LRBF-U) scheme for solving convection dominated CDE. In this method, the entire CDE operator is discretized over the nodes in the upwind local support domain for strongly convection dominant problems. The variable (optimal) shape parameter for LRBF-U scheme has been obtained by using a local optimization algorithm developed by the authors. It has been observed that for highly convection dominated problems, the LRBF-U scheme produces stable and accurate results. The proposed scheme is also been compared with the conventional Central-Upwind combined scheme, to demonstrate its superiority in generating high accurate solutions than the latter. © 2014 Elsevier Ltd.
Local radial basis function based gridfree scheme for unsteady incompressible viscous flows
A 'local' radial basic function (RBF) based gridfree scheme has been developed to solve unsteady, incompressible Navier-Stokes equations in primitive variables. The velocity-pressure decoupling is obtained by making use of a fractional step algorithm. The scheme is validated over a variety of benchmark problems and found a very good agreement with the existing results. Comparisons with the benchmark solutions show that the developed local RBF gridfree scheme is stable and produces accurate results on domains discretized even with non-uniform distribution of nodal points. © 2008 Elsevier Inc. All rights reserved.
Local RBF-FD solutions for steady convection-diffusion problems
This paper describes the application of radial basis function (RBF) based finite difference type scheme (RBF-FD) for solving steady convection-diffusion equations. Numerical studies are made using multiquadric (MQ) RBF. By varying the shape parameter in MQ, the accuracy of the solution is seen to be highly improved for large values of Reynolds' numbers. The developed scheme has been compared with the corresponding finite difference scheme and found that the solutions obtained using the former are non-oscillatory. Copyright © 2007 John Wiley & Sons, Ltd.