| 1. |
- Andersson, Björn O, 1982, et al.
(författare)
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A Modified TAB Model for Simulation of Atomization in Rotary Bell Spray Painting
- 2013
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Ingår i: Journal of Mechanical Engineering and Automation. - 2163-2413. ; 3:2, s. 54-61
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Tidskriftsartikel (refereegranskat)abstract
- The Rotary bell spray applicator technique is commonly used in the automotive industry for paint application because of its high transfer efficiency and high-quality result. The bell spins rapidly around its axis with a tangential velocity at the edge in the order of 100 m/s. The paint falls off the edge and enters the air with a large relative velocity, driving the atomization into small droplets where the resulting size distribution depends on the process conditions. Especially the rotation speed of the bell is an important parameter governing the size distribution. The main research question in this work is to investigate if the Taylor Analogy Breakup (TAB) model can be used to predict the resulting droplet size distributions in spray painting. As the paint is a viscous fluid a modification of the TAB model taking non-linear effects of large viscosity into account is proposed. The parameters in the breakup model are tuned by optimization to match droplet size distributions obtained in CFD simulations with measured ones. Results are presented for three cases with rotation speeds from 30 to 50 thousand RPM where the full droplet size distributions are compared with measurements. Good results are obtained for all three cases where the simulated size distributions compare well to measurements over a wide range of droplet sizes. The TAB method is able to quantitatively predict the result of the breakup process and can be used in a preprocessing stage of a full spray painting simulation, thereby reducing the need for costly and cumbersome measurements.
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| 2. |
- Andersson, Björn O, 1982
(författare)
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Droplet Breakup in Automotive Spray Painting
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Paint and surface treatment processes in a car paint shop are to a largeextent automated and performed by robots. Having access to tools thatincorporate the flexibility of robotic path planning with fast and efficientsimulation of the processes is important to reduce the time required forintroduction of new car models, reduce the environmental impact and increasethe quality. The current version of the software for simulation of spraypainting developed at the Fraunhofer-Chalmers Centre relies on measureddroplet size distributions that can be used as input to the simulations. Thisthesis discusses techniques that can be used to simulate the droplet sizedistributions and therefore reduce the need for costly and complicatedmeasurements.Surface tension plays an important role during breakup as it acts to stabilizethe droplets. On the small scales of droplets from 1-100 µm indiameter it is a strong force yet localized to the interface between thedroplet and the surrounding medium. It is therefore crucial to have controlover the interface and to this end a novel method for reconstructing theinterface of the droplet is described. The method relies on approximation byRadial Basis Functions using a technique that enables the omission of smalllength scale structures in order to obtain a smooth representation that issuitable for numerical discretization.Droplet size distributions have been simulated with the Taylor Analogy Breakup(TAB) model with promising results. A modification taking into account thelarge viscosity of the paint is introduced and the parameters of the model aretuned to the case of rotary bell spray painting commonly used in automotiveindustry. Results show that the model is able to capture the overall shape ofthe size distributions and that it captures the effect of the bell rotationspeed, shifting the distributions toward larger or smaller droplets.
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| 3. |
- Andersson, Björn O, 1982
(författare)
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Modeling and simulation of rotary bell spray atomizers in automotive paint shops
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The paint and surface treatment processes in automotive paint shops are characterized by multiphase and free surface flows, multiphysics interactions, multiscale phenomena, and large moving geometries. The current version of the software for simulation of spray painting developed at the Fraunhofer-Chalmers Centre relies on measurements of droplet size distributions and velocity profiles below the applicator that can be used as input to the simulations. This thesis discusses techniques that can be used to reduce the need for costly and complicated measurements by performing detailed simulations instead.Surface tension plays an important role during breakup as it acts to stabilize the droplets. On the small scales of droplets from 1-100 μm in diameter it is a strong force yet localized to the interface between the droplet and the surrounding medium. It is therefore crucial to have control over the interface and to this end a novel method for reconstructing the interface of the droplet is proposed. The method relies on approximation by Radial Basis Functions using a technique that enables the omission of small length scale structures in order to obtain a smooth representation that is suitable for numerical discretization.Droplet size distributions have been simulated with the Taylor Analogy Breakup model. A modification taking the large viscosity of the paint into account is introduced to the model and it is applied to the case of rotary bell spray painting commonly used in automotive industry. Results show that the model is able to capture the overall shape of the size distributions, as well as the local spatial dependencies on the size distributions where large droplets are typically found further away from the center.By gaining a better understanding of the physical conditions close to the paint applicator the need for costly and complicated measurements is decreased. Having access to tools for fast and efficient simulation of the spray painting processes would be advantageous, since such tools can contribute to reduce the time required for introduction of new models, reduce the cycle time, reduce the environmental impact, and increase quality.
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| 4. |
- Andersson, Björn O, 1982, et al.
(författare)
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Modeling Surface Tension in SPH by Interface Reconstruction using Radial Basis Functions
- 2010
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Ingår i: Proceedings of the 5th International SPHERIC Workshop, 22-25 June 2010, Manchester, U.K., edited by B. D. Rogers. ; , s. 7-14
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- A novel method for reconstructing the interface between two fluids is described and evaluated. The method uses a different basis for approximating the color function than what is common practice in SPH simulations. The key feature of the new method is the ability to omit small length scale structures in order to obtain a smoother representation. A smoother interface is more suitable to derive a surface tension force from, as the magnitude of the force is proportional to the curvature which is related to the second derivative along the interface.
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| 5. |
- Andersson, Björn O, 1982, et al.
(författare)
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Modified TAB Model for Viscous Fluids applied to Breakup in Rotary Bell Spray Painting
- 2012
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Ingår i: ICLASS 2012 - 12th International Conference on Liquid Atomization and Spray Systems.
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Konferensbidrag (refereegranskat)abstract
- The Taylor Analogy Breakup (TAB) model is applied to droplet breakup in rotary bell spray painting commonly used in the automotive industry. The bell spins rapidly around its axis with a tangential velocity at the edge in the order of 100 m/s. The paint falls off the edge and enters the air with a large relative velocity, driving the atomization. The paint is a viscous fluid and a modification of the TAB model taking non-linear effects of large viscosity into account is described. The parameters in the breakup model are tuned to match droplet size distributions obtained in CFD simulations with measured ones. Results are presented for three cases with rotation speeds from 30 to 50 thousand RPM where the full droplet size distributions are compared with measurements. Good results are obtained for all three cases where the simulated size distributions compare well to measurements over a wide range of droplet sizes. The obtained results can be used in a preprocessing stage of a full spray painting simulation thereby reducing the need for costly and cumbersome measurements.
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| 6. |
- Andersson, Björn O, 1982, et al.
(författare)
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MPI-Parallelization of a Structured Grid CFD Solver including an Integrated Octree Grid Generator
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- An existing Computational Fluid Dynamics (CFD) solver is parallelized by means of MPI. The solver includes a dynamic and adaptive grid generator for Cartesian Quadtree and Octree grids, which therefore also have to be parallelized. The grid generator generates grids fulfilling a specific set of rules, that have to be enforced also in parallel. The assembly of the large sparse matrices resulting from the implicit discretization of Navier-Stokes equations is done in parallel, as is the solving process. The parallel performance of both of these processes depends heavily on a good load balancing in order to reach satisfactory speedup. Two versions of load balancing are demonstrated, one based on block swapping, and the other by utilizing the Metis or Parmetis software packages for load balancing of graphs. Results are presented for load balancing and for the parallel speedup of solving the linear algebra system of equations.
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| 7. |
- Edelvik, Fredrik, 1972, et al.
(författare)
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An improved method for dipole modeling in EEG-based source localization
- 2009
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Ingår i: International Federation for Medical and Biological Engineering Proceedings. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 1680-0737. - 9783642038884 ; 25:9, s. 146-149
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Konferensbidrag (refereegranskat)abstract
- The inverse problem in EEG-based source localizationis to determine the location of the brain sources that areresponsible for the measured potentials at the scalp electrodes.The brain sources are usually modeled as current dipoles whichlead to a singularity in the right-hand side of the governing Poisson’sequation. Subtraction methods have been proposed as aremedy and in this paper an improved subtraction method formodeling the dipoles is presented. The accuracy is demonstratedfor radial and tangential sources in layered sphere models and isto the best of the authors’ knowledge superior to previous methodsfor superficial sources. An additional advantage is that itproduces a right hand side with few non-zeros which is beneficialfor efficient solution of the inverse problem.
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| 8. |
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| 9. |
- Jakobsson, S, et al.
(författare)
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Combustion engine optimization: A multiobjective approach
- 2010
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Ingår i: Optimization & Engineering. - : Springer Science and Business Media LLC. - 1389-4420 .- 1573-2924. ; 11:4, s. 533-554
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Tidskriftsartikel (refereegranskat)abstract
- To simulate the physical and chemical processes inside combustion engines is possible by appropriate software and high performance computers. For combustion engines a good design is such that it combines a low fuel consumption with low emissions of soot and nitrogen oxides. These are however partly conflicting requirements. In this paper we approach this problem in a multi-criteria setting which has the advantage that it is possible to estimate the trade off between the different objectives and the decision of the optimal solution is postponed until all possibilities and limitations are known. The optimization algorithm is based on surrogate models and is here applied to optimize the design of a diesel combustion engine.
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| 10. |
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