| 1. |
- Andersson, Anders G., et al.
(författare)
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Flow through a two-scale porosity material
- 2009
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Ingår i: Research Letters in Materials Science. - : Hindawi Limited. - 1687-6822 .- 1687-6830.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Flow through a two-scale porous medium is here investigated by a unique comparison between simulations performed with computational fluid dynamics and the boundary element method with microparticle image velocimetry in model geometries.
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| 2. |
- Andersson, Anders G., et al.
(författare)
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Fluid flow through porous media with dual scale porosity
- 2008
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Ingår i: Proceedings of the 19th International Symposium on Transport Phenomena (ISTP-19). - : University of Iceland, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science.
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Konferensbidrag (refereegranskat)abstract
- Flow in two scale porous media takes place in applications such as advanced composites manufacturing. Knowledge of this flow is of general importance and is crucial for filtration mechanisms when functional filler-particles are added to the liquid resin impregnating the fibrous preform. Means to model and experimentally visualise this flow is here investigated. In particular simulations performed with computational fluid dynamics and the boundary element method are compared to micro particle image velocimetry in a model geometry.
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| 3. |
- Thungström, Göran, et al.
(författare)
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Fabrication and Characterization of thin delta E-Detectors for Spectroscopic Application
- 2005
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 546:1-2, s. 312-318
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Tidskriftsartikel (refereegranskat)abstract
- Ultra thin delta E-detectors for spectroscopic applications have been fabricated and characterized down to a thickness of 4.5 μm. A common one-side mask aligner was in use to fabricate the detectors. The detectors display low leakage current and the resulting capacitance is close to the detector window capacitance below a threshold voltage. The detector telescope should be slightly tilted to reduce the probability for channeling. However, even better control of the thickness uniformity is needed to improve the resolution in the E-E detector telescope
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| 4. |
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| 5. |
- Westerberg, Lars-Göran, et al.
(författare)
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3D MHD reconnection model coupled with Cluster multi-spacecraft data : 3D reconnection model
- 2008
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 113
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Tidskriftsartikel (refereegranskat)abstract
- We present a model where a three-dimensional viscous/resistive analytical model of the large scale plasma flow in the outflow region about a reconnection site at the dayside magnetopause, is coupled with multi-spacecraft measurements from the Cluster satellite armada. A total of ten magnetopause crossings have been analyzed during the period 10:29-11:05 UT January 26, 2001, where nine are shown to be suitable to be coupled with the analytical model. Five of these nine reconnection events results in a successful coupling. By fitting the analytical expressions of the plasma velocity and magnetic field behaviour during the transition of the magnetopause, with data from the Cluster spacecraft we obtain estimates of the location of the X-line together with estimates on the anomalous transport coeffcients of kinematic viscosity (v) and magnetic diffusivity (ηd). We also obtain the development of the magnetopause transition layer away from the X-line. It is shown that the distance from the spacecraft to the X-line varies between 0.01 and 1 Earth radii, while v + ηd have a value between 4 . 104 km2/ s and 4 . 106 km2/ s. Furthermore it is shown that the transition layer thickness follows the analytical pattern where it grows proportional to the square root of the distance from the reconnection site. The estimated thickness obtained from each spacecraft is shown to follow the analytical structure well.
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| 6. |
- Westerberg, Lars-Göran, et al.
(författare)
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A three-dimensional analysis of the flow past an open terrestrial magnetopause
- 2006
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 72:3, s. 359-382
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Tidskriftsartikel (refereegranskat)abstract
- We present a three-dimensional analysis covering an investigation of the behavior of the magnetosheath plasma velocity and the magnetic field during the transfer from the magnetosheath to the magnetosphere. magnetic reconnection is assumed to occur at an arbitrary line parallel to the $y$-axis, located in a region along the magnetopause stretching from the sub-solar point to the north. we do not focus on the process itself, but on its implications for the plasma flow and the magnetic field outside the diffusion region. viscosity and resistivity are included in the magnetohydrodynamic equation of motion as non-ideal effects. the governing equations are solved approximately using the method of asymptotic expansions, with expansion in orders of large reynolds and lundquist numbers. we present two classes of solutions describing the properties north and south of the reconnection line, respectively. results are presented for two locations of the reconnection line at distances of two and seven earth radii from the sub-solar point correspondingly. it is shown that the velocity increases faster north of the reconnection line, and that the effect intensifies as the location of the reconnection line moves further away from the sub-solar point. it is also shown for this case, that there is less variation of the magnetic field and an increase in the field strength.
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| 7. |
- Westerberg, Lars-Göran, et al.
(författare)
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A two dimensional analysis of the compressible flow near a reconnection site at the dayside magnetopause
- 2007
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 73:1, s. 89-115
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Tidskriftsartikel (refereegranskat)abstract
- An improvement of an existing three-dimensional analytical model describing the solar wind flow near a reconnection site at the dayside magnetopause is reported. Introducing an arbitrary orientation of the reconnection line, general solutions for the plasma velocity and magnetic field during the transition of the magnetopause are presented, together with the development of the magnetopause transition layer away from the reconnection site.
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| 8. |
- Westerberg, Lars-Göran, et al.
(författare)
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A two-dimensional analysis of the flow past an open terrestrial magnetopause
- 2005
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Ingår i: Journal of Plasma Physics. - 0022-3778 .- 1469-7807. ; 71:5, s. 537-562
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Tidskriftsartikel (refereegranskat)abstract
- A study of the two-dimensional incompressible flow of the solar wind past an open terrestrial magnetosphere is presented. The plasma is described by the magnetohydrodynamic (MHD) equations including non-ideal effects such as resistivity and viscosity. The theoretical analysis is based on an ordinary perturbation technique with expansion in orders of large Reynolds and Lundqvist numbers. Magnetic reconnection is assumed to occur at an arbitrary point along a region of the magnetopause, stretching from the sub-solar point to the north. From the analysis we find analytical solutions describing the transition layers north and south of a reconnection point. It is shown that the transition layer north of the reconnection point is thinner than the layer on the south side. It is also shown that in order for steady reconnection to occur, the velocity at the reconnection point must be less than the Alfvén velocity. Using the method of matched asymptotic expansions, we match the transition layer solution with a potential flow solution describing the flow and magnetic field in the exterior magnetosheath.
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| 9. |
- Westerberg, Lars-Göran, et al.
(författare)
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Effects of varying magnetosheath flow and dissipation on the two-dimensional reconnection structure at the magnetopause
- 2009
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 16:5, s. 052902-1
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Tidskriftsartikel (refereegranskat)abstract
- The stationary Riemann problem including dissipation in form of resistivity and viscosity for the reconnection structure at the dayside magnetopause is considered. Including tangential velocity shear and gradients across the complete reconnection structure from the magnetosheath side into the magnetosphere, it is shown how dissipation affects the thickness of the intermediate shock wave in the vicinity of a reconnection site. We present how plasma flow structure undergoes a significant change for a nonzero uniform plasma velocity and velocity gradient. It is also shown how the reconnection rate changes and leads to a cutoff when the velocity becomes Alfvénic.
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| 10. |
- Westerberg, Lars-Göran, et al.
(författare)
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Hall effects on the steady structure of the rotational layer at the dayside magnetopause
- 2007
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 14
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Tidskriftsartikel (refereegranskat)abstract
- The influence of the Hall term in the generalized Ohm's law on the large-scale plasma flow during conditions of ongoing magnetic reconnection at the dayside magnetopause (MP) is investigated. Of special interest is the plasma flow behavior during the transition of the MP transition layer as the Hall effect grows in proportion to the viscous-resistive effects. The governing equations are solved approximately by an ordinary perturbation expansion in orders of large Reynolds and Lundqvist numbers. It is shown that the flow pattern is strongly dependent on the magnitude of the Hall parameter; as it approaches zero, the viscous-resistive solution is obtained, while for an ordering of the same magnitude as the resistivity/viscosity, the Hall effect begins to affect the flow structure severely. For an increasing value on the Hall parameter, oscillations are brought into the system, an effect that is enhanced with the magnitude of the Hall parameter. Furthermore, it is shown that as the Hall effect begins to dominate, the transition layer thickens.
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