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In the design process of hydrodynamical and aerodynamical technical applications, the numerical simulation of massively separated vortical flow is crucial for predicting, for example, lift or drag. To obtain reliable numerical results, it is mandatory to accurately predict the physical behavior of vortices. Thus, the dominant vortical flow structures have to be resolved in detail, which requires a local grid refinement and certain adaptation techniques. In this paper, a vortex flow structure adaptation algorithm is presented, which is particularly designed for local grid refinement at vortex axes positions and associated vortex core border locations. To this end, a fast and efficient vortex axis detection scheme is introduced and the algorithm for the vortex core border determination is explained. As the interaction between vortices makes the assignment of grid points to a certain vortex axis difficult, a helicity‐based vortex distinction approach in combination with a geometrical rotational sensor is developed. After describing the combined different techniques in detail, the vortex feature adaptation algorithm is applied to analytical and more realistic examples, which show that the described grid adaptation algorithm is able to enhance the grid cell resolution locally such that all significant vortical flow phenomena are resolved. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Sign and magnitude of the average magnetic hyperfine field Hhf of57Fe in Tb(1?x)Cox intermetallic compounds have been investigated by Mössbauer spectroscopy. For x>0.5, Hhf decreases linearly with increasing Tb concentration. The sign changes from positive for x<0.8 to negative for x>0.8. These trends are discussed in terms of a simple rigid-band model of the Tb(1?x)Cox intermetallics. 相似文献
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Schmidt S Liu T Rütten S Phan KH Möller M Richtering W 《Langmuir : the ACS journal of surfaces and colloids》2011,27(16):9801-9806
Charged poly(N-isopropylacrylamide-co-methacrylic acid) [P(NiPAM-co-MAA)] microgels can stabilize thermo- and pH-sensitive emulsions. By placing charged units at different locations in the microgels and comparing the emulsion properties, we demonstrate that their behaviors as emulsion stabilizers are very different from molecular surfactants and rigid Pickering stabilizers. The results show that the stabilization of the emulsions is independent of electrostatic repulsion although the presence and location of charges are relevant. Apparently, the charges facilitate emulsion stabilization via the extent of swelling and deformability of the microgels. The stabilization of these emulsions is linked to the swelling and structure of the microgels at the oil-water interface, which depends not only on the presence of charged moieties and on solvent polarity but also on the microgel (core-shell) morphology. Therefore, the internal soft and porous structure of microgels is important, and these features make microgel-stabilized emulsions characteristically different from classical, rigid-particle-stabilized Pickering emulsions, the stability of which depends on the surface properties of the particles. 相似文献
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For two‐phase flow models, upwind schemes are most often difficult do derive, and expensive to use. Centred schemes, on the other hand, are simple, but more dissipative. The recently proposed multi‐stage (MUSTA ) method is aimed at coming close to the accuracy of upwind schemes while retaining the simplicity of centred schemes. So far, the MUSTA approach has been shown to work well for the Euler equations of inviscid, compressible single‐phase flow. In this work, we explore the MUSTA scheme for a more complex system of equations: the drift‐flux model, which describes one‐dimensional two‐phase flow where the motions of the phases are strongly coupled. As the number of stages is increased, the results of the MUSTA scheme approach those of the Roe method. The good results of the MUSTA scheme are dependent on the use of a large‐enough local grid. Hence, the main benefit of the MUSTA scheme is its simplicity, rather than CPU ‐time savings. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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A. Weddemann A. Auge D. Kappe F. Wittbracht A. Hütten 《Journal of magnetism and magnetic materials》2010,322(6):643-19229
In this work, we investigate dynamically the dipolar driven demagnetization process of magnetic multi-core particles by solving the Landau-Lifshitz equation for single-domain particles distributed on a three-dimensional sphere. We analyze the relaxation time in respect to different geometry and material parameters. Further we show that the demagnetization times differ from the behaviour of a single magnetic sphere in the case of low damping. To explain these dynamics nanoparticular systems of different dimensions are investigated. We show that deviations can be attributed to a confinement of the relaxation dynamics to a lower dimensional submanifold of the k-space. 相似文献
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Murty A.R.C. Bulusu Peter Waldstätten Thomas Tricotett Gerhard Schulz 《Tetrahedron letters》2004,45(12):2527-2530
A novel photochemical amide cleavage reaction of (6S)-methoxyascomycin opening a pathway for the selective cleavage of the pipecolic acid, is described. The scope of this reaction with several analogues carrying suitable protecting groups is examined. 相似文献
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Murty A.R.C Bulusu Peter Waldstätten Thomas Tricotet Christophe Rochais Andrea Steck Markus Bacher 《Tetrahedron letters》2004,45(30):5833-5836
6-Vinyl (12) and (5R)- and (5S)-vinylproline (18, 19) analogues of ascomycin are synthesised starting from the known suitably protected (6S)-methoxy-9-hydroxy derivative (4) of ascomycin. The strategy involves hydrolytic cleavage of the Cε-N bond of the pipecolic acid moiety, extension of the amino acid side chain by two or one carbon units, functional group manipulations, Pd-catalysed reinstallation of the Cε-N or Cδ-N bonds, followed by deprotection and oxidation. 相似文献
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J. Ellrich R. Kruk R. A. Brand H. Hahn A. Hütten Y. Lei 《Hyperfine Interactions》2012,211(1-3):135-145
The purpose of this communication is to show that arrays of FePt with perpendicular anisotropy can be studied using energy-selective conversion electron M?ssbauer spectroscopy. Magnetic nanostructures have been in the focus of technology and science for many years. One of the economically and comparably scientifically most demanding application of these structures is in storage devices such as hard-disks and MRAMs. The FePt nanodisks presented here show a combination of material and magnetic properties which enable the fabrication of highly ordered nanostructures. 相似文献