Convection of local level set function for moving surfaces and interfaces in forming flow

Reprinted with permission from AIP Conf. Proc. May 17, 2007 -- Volume 908, pp. 61-66 MATERIALS PROCESSING AND DESIGN; Modeling, Simulation and Applications; NUMIFORM '07; Proceedings of the 9th International Conference on Numerical Methods in Industrial Forming Processes; doi:10.1063/1.2740790 Copyright 2007 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of PhysicsInternational audienceWe propose to improve the Level Set method by introducing a convective derivative in the reinitialisation equation. Our approach allows to keep an unitary gradient for Level Set function at the interface. In this way, it is not necessary to regularize periodically the level set since the basic properties are preserved when it is convected. Moreover a local Level Set is introduced by using a sinus like function which enables to ensure a smooth transition. Examples are given in the context of finite element method for forming applications

Adaptive anisotropic meshing for incompressible navier stokes using a VMS solver with boundary layer

International audienceIn this work, we propose to show that adaptive anisotropic meshing based on a posteriori estimation can be addressed for incompressible Navier Stokes at High Reynolds number. The proposed a posteriori estimate is based on the length distribution tensor approach and the associated edge based error analysis. It will be shown that boundary layer can be produced automatically on an unstructured mesh basis. The Finite Element flow solver is based on a Variational MultiScale (VMS) method, which consists in here of decomposition for both the velocity and the pressure fields into coarse/resolved scales and fine/unresolved scales. This choice of decomposition is shown to be favourable for simulating flows at high Reynolds number. The stabilization parameters are determined rigorously taking into account the anisotropy of the mesh using a directional element diameter

Mesh immersion technique for 3D moving domain calculation and applications to twin-screw extrusion and mixing

International audienceThis work is concerned with the development of numerical techniques devoted to the simulation of the flow of a polymer melt in mixing processes such as twin-screw extrusion. In mixing or twin extrusion process simulation, the absence of symmetry of the moving boundaries (the screws) implies that their rigid body motion has to be taken into account by using a special treatment. In this study, we introduce a new technique called Mesh Immersion Technique (MIT), which consists in : a) using a P1+/P1-based (MINI-element) mixed finite element method for solving the velocity-pressure problem, b) solving the problem in the whole barrel cavity and imposing a rigid motion (rotation) to nodes found located inside the so called immersed domains. Each sub-domain (screw) is represented by a surface mesh. The independent meshes are immersed into a unique background computational mesh by calculating the P1 approximation of the function giving the distance to their respective surfaces. A multiphase approach, combined with parallel computing, is used to compute the flow of generalized Newtonian fluids in a complex system such as a twin screw extruder or a batch mixer, including moving free surfaces

Stabilised Finite Element for High Reynolds Number, LES and Free Surface flow Problems

Avalaible on: http://web.univ-ubs.fr/limatb/EG2M/Disc_Seminaire/ECCOMAS-CFD2010/papers/01019.pdfInternational audienceWe propose a stabilized finite element method to address complex high Reynolds flows with free surface. An implicit stabilized finite element method (SFEM) is used for solving the incompressible two-phase Navier-Stokes equations in three-dimensions. A novel approach to deal with turbulent two-phase flows is highlighted by coupling a local convected levelset method to a Large Eddy simulation turbulent modeling. A comparison between the static and dynamic eddy-viscosity models is analyzed. We assess the behaviour and accuracy of the proposed stabilized finite element method coupled to the two-phase turbulent approximation in the simulation of complex 3D flows, such as the flow in a partially filled two communicating tanks. Results are compared with the experimental data and show that the present implementation is able to exhibit good stability and accuracy properties for high Reynolds number flows using unstructured meshes

Simulations numériques d'écoulements de fluides complexes à l'échelle microscopique : un nouvel outil de rhéologie

National audienceUne méthode de simulation numérique directe a été développée pour l'écoulement de fluides fortement chargés, avec plusieurs populations de particules (fibres et sphères), pouvant entrer en collision. Ce fluide complexe modélise les écoulements de BMC (Bulk Molding Compound) utilisés par Schneider Electric. Une approche par domaines fictifs, avec des conditions limites périodiques, a été utilisée

3D monolithic finite element approach for aero-thermics processes in industrial furnaces

The original publication is available at: http://www.esaim-proc.org/articles/proc/pdf/2011/04/proc113304.pdfInternational audienceWe consider in this paper a mathematical and numerical model to design an industrial software solution able to handle real complex furnaces configurations in terms of geometries, atmospheres, parts positioning, heat generators and physical thermal phenomena. A three dimensional algorithm based on stabilized finite element methods (SFEM) for solving the momentum, energy, turbulence and radiation equations is presented. An immersed volume method (IVM) for thermal coupling of fluids and solids is introduced and detailed. It consists in considering a single 3D grid of the furnace and solving one set of equations for both fluid and solid with different thermal properties. A fast anisotropic mesh adaptation algorithm based on the variations of the level set function is applied to ensure an accurate capture of the discontinuities at the fluid-solid interfaces. The proposed method demonstrates the capability of the model to simulate an unsteady three dimensional heat transfers and turbulent flows in an industrial furnace with the presence of conducting solids. Temperature measurements were carried in different locations and are compared to the experimental results

Multiscale simulation of mixing processes using 3D-parallel, fluid-structure interaction techniques

International audienceThis work focuses on the development of a general finite element code, called Ximex®, devoted to the three-dimensional direct simulation of mixing processes of complex fluids. The code is based on a simplified fictitious domain method coupled with a "level-set" approach to represent the rigid moving boundaries, such as screws and rotors, as well as free surfaces. These techniques, combined with the use of parallel computing, allow computing the time-dependent flow of generalized Newtonian fluids in large and complex processes, involving moving free surfaces which are treated by a level-set/Hamilton-Jacobi method. Two flow case studies will be presented in this paper: the flow within a twin-screw extruder and the flow in a batch mixer

Massively parallel computation on anisotropic meshes

International audienceIn this paper, we present developments done to obtain efficient parallel computations on supercomputers up to 8192 cores. While most massively parallel computation are shown using regular grid it is less common to see massively parallel computation using anisotropic adapted unstructured meshes. We will present here two mains components done to reach very large scale calculation up to 10 billions unknowns using a muligrid method over unstructured mesh running on 8192 cores. We firstly focus on the strategy used to generate computational meshes and in particular anisotropic ones adapted to capture a quite complicated test function. Then we will briefly describe a parallel multigrid method. Performance test over a large range of cores from 512 to 8192 cores is then presented using the French national supercomputers Jade and Curie. The last section will present a calculation done on smallest number of cores on our own cluster, but using more realistic data obtain directly from experimentation. The goal is to be able to realize such kind of simulation on really complex micro structure obtain by tomography at a larger scal

Stabilized Finite Element Methods vs LES modelling for fluid-strucure interaction with anisotropic adaptive meshing

National audienceThis paper presents a stabilised finite element method for the solution of incompressible multiphase flow problems in three dimensions using an immersed volume method with anisotropic adaptive meshing. A recently developed stabilised finite element solver which draws upon features of solving general fluid-structure interactions is presented. The proposed method is developed in the context of the monolithic formulation. Such strategy gives rise to an extra stress tensor in the Navier-Stokes equations coming from the presence of the structure in the fluid. The distinctive feature of the Variational MultiScale approach is not only the decomposition for both the velocity and the pressure fields into coarse/resolved scales and fine/unresolved scales but also the possible efficient enrichment of the extra constraint. This choice of decomposition is shown to be favorable for simulating multiphase flows at high Reynolds number. We assess the behaviour and accuracy of the proposed formulation coupled to the levelset method approximation in the simulation of 2D and 3D time-dependent numerical examples such as : vortex shedding behind an obstacle, conjugate heat transfer inside industrial furnaces and the rigid bodies motion in incompressible flows.See http://hal.archives-ouvertes.fr/docs/00/59/26/96/ANNEX/r_Q1R43125.pd

Stabilized Finite Elements Method For High Reynolds Free Surface Flows

Available on: http://congress.cimne.com/CMWR2010/frontal/default.aspInternational audienceWe propose a stabilized finite element method to address complex high Reynolds flows with free surface. An implicit stabilized finite element method (SFEM) is used for solving the incompressible two-phase Navier-Stokes equations in three-dimensions. A novel approach to deal with turbulent two-phase flows is highlighted by coupling a local convected levelset method to a Large Eddy simulation turbulent modeling. A comparison between the static and dynamic eddy-viscosity models is analyzed. We assess the behaviour and accuracy of the proposed stabilized finite element method coupled to the two-phase turbulent approximation in the simulation of complex 3D flows, such as the flow in a partially filled two communicating tanks. Results are compared with the experimental data and show that the present implementation is able to exhibit good stability and accuracy properties for high Reynolds number flows using unstructured meshes