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| 2. |
- Andersson, Tommy, et al.
(author)
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Multiobjective Optimization of a Heat-Sink Design Using the Sandwiching Algorithm and an Immersed Boundary Conjugate Heat Transfer Solver
- 2018
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In: Journal of Heat Transfer. - : ASME International. - 1528-8943 .- 0022-1481. ; 140:10, s. 102002 -
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Journal article (peer-reviewed)abstract
- The thermal management is an ever increasing challenge in advanced electronic devices. In this paper, simulation-based optimization is applied to improve the design of a plate-fin heat-sink in terms of operational cost and thermal performance. The proposed framework combines a conjugate heat transfer solver, a CAD engine and an adapted Sandwiching algorithm. A key feature is the use of novel immersed boundary (IB) techniques that allows for automated meshing which is perfectly suited for parametric design optimization.
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| 3. |
- Johnson, Tomas, 1979, et al.
(author)
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A finite volume method for electrostatic three species negative corona discharge simulations with application to externally charged powder bells
- 2015
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In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886. ; 74, s. 27-36
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Journal article (peer-reviewed)abstract
- A three species model for steady-state negative corona discharge is studied. Ionization, attachment, and recombination reactions are modeled. A novel unstructured finite volume algorithm to solve the equations is presented, using the secondary emission of electrons from the cathode to set boundary values for the electrons.To show the usefulness of the method for industrial applications it is used to characterize the electrostatic properties of an externally charged rotary powder bell used in the automotive industry. Experimental current density profiles are reconstructed with good accuracy, which validates the model and the method with real experimental data.
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| 4. |
- Johnson, Tomas, 1979, et al.
(author)
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A Multi-Scale Simulation Method for the Prediction of Edge Wicking in Multi-Ply Paperboard
- 2015
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In: Nordic Pulp and Paper Research Journal. - 2000-0669 .- 0283-2631. ; 30:4, s. 640-650
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Journal article (peer-reviewed)abstract
- 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.
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| 5. |
- Johnson, Tomas, 1979, et al.
(author)
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Simulation of the spherical orientation probability distribution of paper fibers in an entire suspension using immersed boundary methods
- 2016
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In: Journal of Non-Newtonian Fluid Mechanics. - : Elsevier BV. - 0377-0257. ; 229, s. 1-7
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Journal article (peer-reviewed)abstract
- A numerical model based on the Fokker–Planck equation for studying the orientation of paper fibers in a suspension is presented. The model is implemented in a finite volume framework. The rotational operators are discretized on a triangulated half sphere and the spatial operators are discretized on a Cartesian octree grid, where internal walls are handled with immersed boundary methods. Transient solutions of the two dimensional fiber orientation distribution are computed in the entire fluid domain. This is in contrast to earlier approaches that either only compute along streamlines or one dimensional projected orientations. The fibers are assumed to have negligible inertia and thus to follow the fluid perfectly and to be evenly distributed. A head-box geometry relevant for paper forming is used to exemplify the usefulness of the method. The influence of translational and rotational diffusion is included in the presented method.
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| 6. |
- Svedung Wettervik, Benjamin, 1990, et al.
(author)
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A domain decomposition method for three species modeling of multielectrode negative corona discharge with applications to electrostatic precipitators
- 2015
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In: Journal of Electrostatics. - : Elsevier BV. - 0304-3886. ; 77, s. 139-146
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Journal article (peer-reviewed)abstract
- The negative corona discharge problem for multi-electrode geometries is modeled by a three speciesmodel. The equations are solved using domain decomposition, by recognizing that multiple species areonly present in a small part of the domain, and hence only need to be incorporated locally in the model.The method is applied to an industrially relevant three wire electrostatic precipitator geometry. Thecalculated current density is in good agreement with experimental data. To further illustrate applicationsof the three species solution, it is used for coupled particle, fluid, and electrostatic simulations to analyzeparticle collection properties.
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