| 1. |
|
|
| 2. |
- Kettil, Gustav, 1990, et al.
(författare)
-
A Multiscale Method for Discrete Fiber Network Models
- 2018
-
Ingår i: 6th European Conference on Computational Mechanics (Solids, Structures and Coupled Problems). 7th European Conference on Computational Fluid Dynamics, 11-15 June 2018, Glasgow, UK.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The mechanics of paper depends on the properties of its fibers and bonds. Modeling paper as a network [1] will include effects of single fibers and bonds, capturing heterogeneous properties. In the ISOP (Innovative Simulation of Paper) project at Fraunhofer-Chalmers Centre, the forming process is simulated [2, 3]. To investigate the mechanical properties of the resulting simulated paper sheets a network approach is utilized. Numerical investigation of fiber networks is demanding due to the large number of fibers and bonds, fluctuation of their properties, and the non-regular network structure. Multiscale methods are useful tools to circumvent such problems. In this work a multi-scale approach for fiber networks is developed, based on a FEM-method for continua [4]. Consider a fiber network governed by a model resulting in an equation Kx = F, where K describes the network properties, x are node displacements, and F are applied forces. The idea of the multi-scale method is to consider a subset of all nodes, denoted coarse nodes, which in turn represents a coarse grid. At each coarse node a basis function is defined similarly as in the finite element method. By solving a system including the coarse nodes an approximation would be attained, however this approximation would leave out the fine scale effects of the heterogeneous network. Instead the coarse basis functions are modified by solving a local system at each coarse node, including surrounding fine nodes. These modified basis functions are thereafter used when solving the global system, resulting in an approximation of the network displacements now including effects from the fine scale.
|
|
| 3. |
- Kettil, Gustav, 1990, et al.
(författare)
-
A Multiscale Methodology for Simulation of Mechanical Properties of Paper
- 2020
-
Ingår i: Proceedings of the 6th European Conference on Computational Mechanics: Solids, Structures and Coupled Problems, ECCM 2018 and 7th European Conference on Computational Fluid Dynamics, ECFD 2018. - 9788494731167 ; 2020, s. 2795-2806
-
Konferensbidrag (refereegranskat)abstract
- In this work a multiscale framework developed for simulation of mechanical properties of paper is presented. The framework consists of two major parts. In the first part the forming process of a paper machine is simulated using the fiber suspension model developed in [8]. Fluid dynamics together with an advanced contact calculation method enables detailed simulation of the lay down process. The resulting paper sheet is used as input to the second part of the framework. In the second part the fiber configuration attained from the unique forming simulations is transformed into a network representation, enabling simulation of mechanical properties. The paper mechanics is governed by a fiber network model. To study macroscale properties a novel numerical upscaling method for networks has been developed. In this paper the complete simulation methodology is outlined and discussed.
|
|
| 4. |
- Kettil, Gustav, 1990, et al.
(författare)
-
Detailed Simulations of Early Paper Forming
- 2015
-
Ingår i: COST FP1005 Fibre Suspension Flow Modelling Final Conference Trondheim 2015 June 9-11.
-
Konferensbidrag (refereegranskat)abstract
- Computer simulations are important to increase the knowledge of the processes involved in paper making. Because of the complexity of the paper processes the development of simulation tools requires models and numerical methods which capture as much as possible of the real physical phenomena. In this paper a framework for simulation of fiber suspension flow is presented. The framework is founded on a fluid solver for the Navier-Stokes equations and a fiber model based on finite strain beam theory including shearing. Moreover, the coupling between fibers and fluid is resolved with the immersed boundary method and the interaction between the fibers is calculated using a model based on DLVO-theory.
|
|
| 5. |
- Kettil, Gustav, 1990, et al.
(författare)
-
Novel Contact Forces for Immersed Boundary Paper Forming Simulations
- 2015
-
Ingår i: Online proceedings: http://tappi.sclivelearningcenter.com/; PF2 - The Past, Present and Future of CFD Papermaking; PaperCon 2015 Atlanta April 19-22.
-
Konferensbidrag (refereegranskat)abstract
- To be able to simulate the different processes involved in paper machines, models, numerical methods and algorithms have to be developed which capture as much as possible of the real physical phenomena. In this paper a model for calculation of the chemical and physical interaction between objects included in a fiber suspension is presented. The contact force model is based on DLVO theory [1, 2] and uses so-called contact points distributed along the fiber suspension objects. The contact model has been used in an existing framework to simulate the build-up of low density paper webs. In the framework fibers are modeled as elliptical cylinders whose movements are described by finite-strain beam theory which includes shearing. The fluid flow is computed using a Navier-Stokes solver and immersed boundary methods are utilized to resolve the flow around each fiber. For validation, the air permeability and thickness of the paper webs have been measured and compared with simulated data. The result demonstrates that the software can be used to simulate paper forming.
|
|
