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Spatial Oscillation (spatial + oscillation)
Selected AbstractsNumerical characteristics of a simple finite element formulation for consolidation analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 10 2004Guofu Zhu Abstract The spatial oscillation of values in the consolidation analysis when using small time increments has been a common problem for most existing methods. In this paper, the numerical characteristics of a simple finite element formulation for 1-D consolidation analysis recently proposed by the authors have been examined in detail. This paper proves that the commonly encountered phenomenon of spatial oscillation due to small time increments does not occur in the simple finite element formulation. The criterion of minimum time step used in most existing methods can be eliminated at least for linear situations by using the simple formulation proposed by the authors. Thus, the consolidation analysis can be carried easily for many situations, such as the one involving a relatively impermeable clay layer sandwiched between sandy layers. Copyright © 2004 John Wiley & Sons, Ltd. [source] Experimental observation of a strange temporal oscillation of X-ray Pendellösung fringesJOURNAL OF SYNCHROTRON RADIATION, Issue 5 2009Jun-ichi Yoshimura As a strange property not explained by existing theories, it has been known from experiment that X-ray moiré and Pendellösung interference fringes show a small spatial oscillation in the beam path in free space that the diffraction image carrying those fringes is propagated after emerging from the crystal. In connection with the investigation into this strange fringe oscillation, it has been found, by an experiment successively recording Pendellösung-fringe topographs using an X-ray CCD camera, that X-ray Pendellösung fringes also show a small temporal oscillation. Characteristics of this temporal Pendellösung-fringe oscillation, namely irregularities in the fringe profile, the manner of fringe oscillation and a reciprocal correlation between oscillation amplitude and fringe contrast, are shown to be very similar to those of the previously reported spatial oscillation of moiré and Pendellösung fringes. Therefore this temporal oscillation is supposed to have the same origin as the spatial oscillation, revealing another section of the same phenomenon. This discovery of the temporal oscillation advances a step nearer to the full understanding of this strange phenomenon, while disclosing a new property of Pendellösung fringes. As well as the above, a three-dimensional profile representation (surface plot) is given of the image of Pendellösung fringes, to make it clear that unidentified fine intensity modulations, called subfringes in this paper, are produced superposed on the main fringe system. Overall inspection of the intensity profiles of the fringe-imaged topographs suggests that temporal intensity oscillations also occur on a more global scale than the extension of individual fringes, as an unidentified action of the wavefield. [source] Simulation of lid-driven cavity flows by parallel lattice Boltzmann method using multi-relaxation-time schemeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2004J.-S. Wu Abstract Two-dimensional near-incompressible steady lid-driven cavity flows (Re = 100,7,500) are simulated using multi-relaxation-time (MRT) model in the parallel lattice Boltzmann BGK Bhatnager,Gross,Krook method (LBGK). Results are compared with those using single-relaxation-time (SRT) model in the LBGK method and previous simulation data using Navier,Stokes equations for the same flow conditions. Effects of variation of relaxation parameters in the MRT model, effects of number of the lattice points, improved computational convergence and reduced spatial oscillations of solution near geometrically singular points in the flow field using LBGK method due to MRT model are highlighted in the study. In summary, lattice Boltzmann method using MRT model introduces much less spatial oscillations near geometrical singular points, which is important for the successful simulation of higher Reynolds number flows. Copyright © 2004 John Wiley & Sons, Ltd. [source] | ||||||||||