A comparison of several numerical methods for the solution of the Convection-Diffusion Equation using the method of finite spheres

In this paper we compare several numerical methods for the solution of the convection-diffusion equation using the method of finite spheres; a truly meshfree numerical technique for the solution of boundary value problems. By conducting numerical inf-sup tests on a one-dimensional model problem it is found that a higher order derivative artificial diffusion (Ho DAD) method performs the best among the schemes tested. This method is then applied to the analysis of problems in two-dimensions.     

An analysis and comparison of conservative upwind difference schemes for ideal and non-ideal gases

In a recent paper [P. Glaister, Conservative upwind difference schemes for the Euler equations, Comput. Math. Appl. 45 (2003) 1673–1682] a number of numerical schemes were presented for the Euler equations governing compressible flows of an ideal gas, the principal one of which is based on a conservative linearisation approach. This scheme was subsequently extended to encompass compressible flows of real gases where the equation of state allows for non-ideal gases [P. Glaister, Conservative upwind difference schemes for compressible flows of a real gas, Comput. Math. Appl. 48 (2004) 469–480]. These schemes use different parameter vectors in their construction and, consequently, the scheme in [P. Glaister, Conservative upwind difference schemes for compressible flows of a real gas, Comput. Math. Appl. 48 (2004) 469–480] when applied to the special case of an ideal gas is not identical to the principal ideal gas scheme in [P. Glaister, Conservative upwind difference schemes for the Euler equations, Comput. Math. Appl. 45 (2003) 1673–1682]. In this paper it is shown how these schemes are related, followed by a numerical comparison when each is applied to two standard test problems.     

Extension of WAF Type Methods to Non-Homogeneous Shallow Water Equations with Pollutant

This paper deals with the extension of the WAF method to discretize Shallow Water Equations with pollutants. We consider two different versions of the WAF method, by approximating the intermediate waves using the flux of HLL or the direct approach of HLLC solver. It is seen that both versions can be written under the same form with different definitions for the approximation of the velocity waves. We also propose an extension of the method to non-homogeneous systems. In the case of homogeneous systems it is seen that we can rewrite the third component of the numerical flux in terms of an intermediate wave speed approximation. We conclude that—in order to have the same relation for non-homogeneous systems—the approximation of the intermediate wave speed must be modified. The proposed extension of the WAF method preserves all stationary solutions, up to second order accuracy, and water at rest in an exact way, even with arbitrary pollutant concentration. Finally, we perform several numerical tests, by comparing it with HLLC solver, reference solutions and analytical solutions.     

A comparison of conservative upwind difference schemes for the shallow water equations

Numerical results are presented and compared for four conservative upwind difference schemes for the shallow water equations when applied to a standard test problem. This includes consideration of the effect of treating part of the flux balance as a source, and a comparison of square-root and arithmetic averaging.