Dante De Santis

Linear and non-linear high order accurate residual distribution schemes for the discretization of the steady compressible Navier-Stokes equations

A robust and high order accurate Residual Distribution (RD) scheme for the discretization of the steady Navier-Stokes equations is presented. The proposed method is very flexible: it is formulated for unstructured grids, regardless the shape of the elements and the number of spatial dimensions. A continuous approximation of the solution is adopted and standard Lagrangian shape functions are used to construct the discrete space, as in Finite Element methods. The traditional technique for designing RD schemes is adopted: evaluate, for any element, a total residual, split it into nodal residuals sent to the degrees of freedom of the element, solve the non-linear system that has been assembled and then iterate up to convergence. The main issue addressed by the paper is that the technique relies in depth on the continuity of the normal flux across the element boundaries: this is no longer true since the gradient of the state solution appears in the flux, hence continuity is lost when using standard finite element approximations. Naive solution methods lead to very poor accuracy. To cope with the fact that the normal component of the gradient of the numerical solution is discontinuous across the faces of the elements, a continuous approximation of the gradient of the numerical solution is recovered at each degree of freedom of the grid and then interpolated with the same shape functions used for the solution, preserving the optimal accuracy of the method. Linear and non-linear schemes are constructed, and their accuracy is tested with the method of the manufactured solutions. The numerical method is also used for the discretization of smooth and shocked laminar flows in two and three spatial dimensions. We propose a very high order accurate methods for the approximation of the compressible Navier-Stokes equations with residual distribution schemes.The memory footprint is lower than for Discontinuous Galerkin like methods.We show uniform accuracy for the whole range of Reynolds numbers.The solution technique is described in details, and we show how to reach excellent convergence.

High-Order Preserving Residual Distribution Schemes for Advection-Diffusion Scalar Problems on Arbitrary Grids

This paper deals with the construction of a class of high-order accurate residual distribution schemes for advection-diffusion problems using conformal meshes. The problems considered range from pure diffusion to pure advection. The approximation of the solution is obtained using standard Lagrangian finite elements and the total residual of the problem is constructed taking into account both the advective and the diffusive terms in order to discretize with the same scheme both parts of the governing equation. To cope with the fact that the normal component of the gradient of the numerical solution is discontinuous across the faces of the elements, the gradient of the numerical solution is reconstructed at each degree of freedom of the grid and then interpolated with the same shape functions used for the solution. Linear and nonlinear schemes are constructed and their accuracy is tested with the discretization of advection-diffusion and anisotropic diffusion problems.

High order residual distribution scheme for Navier-Stokes equations.

In this work we describe the use of the Residual Distribution schemes for the discretization of the conservation laws. In particular, emphasis is put on the construction of a third order accurate scheme. We first recall the proprieties of a Residual Distribution scheme and we show how to construct a high order scheme for advection problems, in particular for the system of the Euler equations. Furthermore, we show how to speed up the convergence of implicit scheme to the steady solution by the means of the Jacobian-free technique. We then extend the scheme to the case of advection-diffusion problems. In particular, we propose a new approach in which the residuals of the advection and diffusion terms are distributed together to get high order accuracy. Due to the continuous approximation of the solution the gradients of the variables are reconstructed at the nodes and then interpolated on the elements. The scheme is tested on scalar problems and is used to discretize the Navier-Stokes equations.

High order preserving residual distribution schemes for the laminar and turbulent Navier Stokes on arbitrary grids

This paper deals with the construction of a class of high order accurate Residual Dis- tribution schemes for the Navier Stokes equations using conformal meshes. The approx- imation of the solution is obtained using standard Lagrangian finite elements, and the total residual of the problem is constructed taking into account both the advective and the diffusive terms in order to discretize within the same scheme both parts of the gov- erning equation. To cope with the fact that the normal component of the gradients of the numerical solution is discontinuous across the faces of the elements, the gradient of the numerical solution is recovered at each degree of freedom of the grid and then interpolated with the same shape functions used for the solution. The procedure is fully described for the scalar case, and formaly extended to the system case. Linear and non-linear schemes are constructed and their accuracy is first tested with the help of manufactured solutions, and then applied to several (2D and 3D) test cases.

Node-pair finite volume/finite element schemes for the Euler equation in cylindrical and spherical coordinates

A numerical scheme is presented for the solution of the compressible Euler equations in both cylindrical and spherical coordinates. The unstructured grid solver is based on a mixed finite volume/finite element approach. Equivalence conditions linking the node-centered finite volume and the linear Lagrangian finite element scheme over unstructured grids are reported and used to devise a common framework for solving the discrete Euler equations in both the cylindrical and the spherical reference systems. Numerical simulations are presented for the explosion and implosion problems with spherical symmetry, which are solved in both the axial-radial cylindrical coordinates and the radial-azimuthal spherical coordinates. Numerical results are found to be in good agreement with one-dimensional simulations over a fine mesh.