Search results for "Eulerian path"
showing 5 items of 25 documents
Numerical Simulation of Friction Stir Welding by Natural Element Methods
2008
In this work we address the problem of numerically simulating the Friction Stir Welding process. Due to the special characteristics of this welding method (i.e., high speed of the rotating pin, very large deformations, etc.) finite element methods (FEM) encounter several difficulties. While Lagrangian simulations suffer from mesh distortion, Eulerian or Arbitrary Lagrangian Eulerian (ALE) ones still have difficulties due to the treatment of convective terms, the treatment of the advancing pin, and many others. Meshless methods somewhat alleviate these problems, allowing for an updated Lagrangian framework in the simulation. Accuracy is not affected by mesh distortion (and hence the name mes…
Meshless Simulation of Friction Stir Welding
2007
This paper encompasses our first efforts towards the numerical simulation of friction stir welding by employing a Lagrangian approach. To this end, we have employed a meshless method, namely the Natural Element Method (NEM). Friction Stir welding is a welding process where the union between the work pieces is achieved through the extremely high deformation imposed by a rotating pin, which moves between the two pieces. This extremely high strain is the main responsible of the difficulties associated with the numerical simulation of this forming process. Eulerian and Arbitrary Lagrangian-Eulerian (ALE) frameworks encounter difficulties in some aspects of the simulation. For instance, these ap…
CFD Simulation of Particle Suspension Height in Stirred Vessels
2004
Computational fluid dynamics (CFD) simulation capabilities for stirred solid–liquid dense systems are explored. These systems may give rise to the formation of a thick and well defined clear liquid layer in the upper part of the vessel, whose extension progressively reduces with increasing impeller speed. Experimental measurements of the suspension height (the height of the particle laden layer) were carried out at various agitation speeds for a variety of solid–liquid systems in a fully baffled transparent tank. A clear layer of liquid was actually observed in all runs, with the suspension height almost linearly dependent on agitation speed. CFD simulations of the above described systems w…
Nonlinear evolution of cosmological inhomogeneities
2008
The nonlinear evolution of a cosmologically significant fluid is studied up to shell crossing. The magnetic part of the Weyl tensor, the pressure and the vorticity vanish. A suitable spatial grid is chosen. The relativistic Ellis equations are particularized on the world lines defined by the nodes of the grid and, then, the resulting equations are numerically solved. The integrations are performed in suitable Lagrangian inertial coordinates, in which the differential equations become ordinary. After the integration, a method to change from Lagrangian to Eulerian coordinates is applied. This approach has been outlined with the essential aim of studying the evolution of large scale cosmologic…
An explicit unconditionally stable numerical solution of the advection problem in irrotational flow fields
2004
[1] A new methodology for the Eulerian numerical solution of the advection problem is proposed. The methodology is based on the conservation of both the zero- and the first-order spatial moments inside each element of the computational domain and leads to the solution of several small systems of ordinary differential equations. Since the systems are solved sequentially (one element after the other), the method can be classified as explicit. The proposed methodology has the following properties: (1) it guarantees local and global mass conservation, (2) it is unconditionally stable, and (3) it applies second-order approximation of the concentration and its fluxes inside each element. Limitati…