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Halmstad, Sweden

Glatt E.,Fraunhofer Institute for Industrial Mathematics | Rief S.,Fraunhofer Institute for Industrial Mathematics | Wiegmann A.,Fraunhofer Institute for Industrial Mathematics | Fredlund M.,Stora Enso | And 3 more authors.
Tappi Journal | Year: 2011

Paper forming is the first step in the paper machine where a fiber suspension leaves the headbox and flows through a forming fabric. Complex physical phenomena occur as the paper forms, during which fibers, fillers, fines, and chemicals added to the suspension interact. Understanding this process is important for the development of improved paper products because the configuration of the fibers during this step greatly influences the final paper quality. Because the effective paper properties depend on the microstructure of the fiber web, a continuum model is inadequate to explain the process and the properties of each fiber need to be accounted for in simulations. This study describes a new framework for microstructure simulation of early paper forming. The simulation framework includes a Navier-Stokes solver and immersed boundary methods to resolve the flow around the fibers. The fibers were modeled with a finite element discretization of the Euler-Bernoulli beam equation in a co-rotational formulation. The contact model is based on a penalty method and includes friction and elastic and inelastic collisions. We validated the fiber model and the contact model against demanding test cases from the literature, with excellent results. The fluid-structure interaction in the model was examined by simulating an elastic beam oscillating in a cross flow. We also simulated early paper formation to demonstrate the potential of the proposed framework. Source


Johnson T.,Fraunhofer Chalmers Center | Mark A.,Fraunhofer Chalmers Center | Nystrom J.,Fraunhofer Chalmers Center | Rief S.,Fraunhofer Institute for Industrial Mathematics | And 8 more authors.
Nordic Pulp and Paper Research Journal | Year: 2015

When liquid packaging board is made aseptic in the filling machine the unsealed edges of the board are exposed to a mixture of water and hydrogen peroxide. A high level of liquid penetration may lead to aesthetic as well as functional defects. To be able to make a priori predictions of the edge wicking properties of a certain paperboard material is therefore of great interest to the paper industry as well as to packaging manufacturers. In this paper an extended multi-scale model of edge wicking in multi-ply paperboard is presented. The geometric and physical properties of the paperboard are modeled on the micro-scale, and include fillers and fines. The absolute air permeabilities and pore size distributions are validated with experimental and tomographic values. On the macro-scale random porosity and sizing distributions, time and sizing dependent contact angles, and inter-ply dependence are modeled. Arbitrary shapes of the paperboard are handled through an unstructured 3D surface mesh. Stationary and transient edge wicking simulations are validated against experiments with excellent agreement. The simulations show that the diffusive menisci between the liquid and air phases together with the two-ply model is necessary to achieve good agreement with the transient edge wicking experiments. Source


Mathieu D.,CNRS Textile Mechanics and Physics Laboratory | Sabri M.,Albany International | Jean-Francois O.,CNRS Textile Mechanics and Physics Laboratory | Jean-Yves D.,CNRS Textile Mechanics and Physics Laboratory
Journal of Industrial Textiles | Year: 2014

3D structures for composites, and especially 3D woven preforms use, is growing because of high-performance fibres improvements, field diversification and applications complexity. Critical industries like the air-space industry need a perfect control of processes and products’ final properties. Among other 3D weaving techniques, multilayer weaving is interesting for the diversity and complexity of possible 3D structures. A new Jacquard shedding technology called UNIVAL 100 which can be used with multilayer weaving, has appeared few years ago and uses actuators instead of the traditional Jacquard hooks. It is synonym of great improvements, as such a technology should enable controlling perfectly the way yarns are moving during shedding. The aim of this paper is first to describe their operating mode. It is our basis for a design of experiments development, the purpose of which is to experimentally determine the effects of UNIVAL parameters on process quality, in the case of high-density multilayer woven fabrics (which we will further call HDMW fabrics). © 2015, © The Author(s) 2015. Source


Svenning E.,Fraunhofer Chalmers Center | Mark A.,Fraunhofer Chalmers Center | Edelvik F.,Fraunhofer Chalmers Center | Glatt E.,Fraunhofer Institute for Industrial Mathematics | And 6 more authors.
Nordic Pulp and Paper Research Journal | Year: 2012

Fiber suspension simulations are challenging since they involve transient fluid flow with immersed solid objects subject to large displacements and rotations. In the present work, a beam model in corotational formulation is coupled with a fluid solver using immersed boundary methods. The model is used to simulate a fiber in a shear flow and excellent agreement is found with Jeffery's equations. The shapes of fibers deforming in a shear flow are found to be in qualitative agreement with shapes observed in experiments. The flow of a fiber suspension is studied by simulating early paper forming with one-way and semi-two-way coupling. It is found that the flow through the fiber web needs to be resolved in order to predict the retention of fibers in the fiber web. Source


Mark A.,Fraunhofer Chalmers Center | Berce A.,Fraunhofer Chalmers Center | Sandboge R.,Fraunhofer Chalmers Center | Edelvik F.,Fraunhofer Chalmers Center | And 10 more authors.
Tappi Journal | Year: 2012

When liquid packaging board is made aseptic in the filling machine, the unsealed edges of the board are exposed to hydrogen peroxide. A high level of liquid penetration may lead to aesthetic as well as functional defects. The ability to make a priori predictions about the edge wicking properties of a certain paperboard material is therefore of great interest to the paper industry, as well as to packaging manufacturers. In this paper, a multi-scale framework is proposed that allows for detailed simulation of the edge wicking process. On the fiber micro-scale, virtual paper models are generated based on input from tomographic and scanning electron microscope (SEM) images. A pore morphology method is used to calculate capillary pressure curves, and on the active pores, one-phase flow simulations are performed for relative permeabilities. The results as functions of saturation and porosity are stored in a database. The database is used as input for two-phase flow simulations on the paper macro-scale. The resulting fluid penetration is validated against pressurized edge wick measurements on paper lab sheets with very good agreement. The proposed multi-scale approach can be used to increase the understanding of how edge wicking in paperboard packages depends on the micro-structure. Source

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