Reservoir formation in shallow granular flows through a contraction

We consider flow of dry granular matter down an inclined chute with a localized contraction. Measurements and analysis show that changes in particle volume fraction are important, especially across granular bores. For fixed upstream conditions and depending on the nozzle width of the contraction, we observe either small oblique jumps, a reservoir with a steady jump, or a reservoir with an upstream traveling bore. Shallow layer theory extended to include porosity changes qualitatively predicts these regimes. Implications for volcanic debris \ud ows are discussed

Noncommuting filters and dynamic modelling for LES of turbulent compressible flow in 3D shear layers

Abstract in publication

Overdracht van lood, cadmium, kwik en arseen van diervoeders naar dierlijke produkten van mestlammeren

In samemo1erking met het IVVO te Lelystad werd nagegaan wat het effekt bij mestlammeren was van toediening van zware metalen via het voer op het gehalte van deze metalen in een aantal dierlijke produkten. Lood, cadmium, kwik en arseen werden toegediend in de vorm van oplosbare verbindingen of zoals ze voorkomen in haven- en rioolslib. De toegediende hoeveelheden bedroegen voor lood, cadmium, kwik en arseen respektievelijk 10, 2, 0,1 en 2 mg/kg droge stof

Modeling and simulation of phase-transitions in multicomponent aluminum alloy casting

The casting process of aluminum products involves the spatial distribution of alloying elements. It is essential that these elements are uniformly distributed in order to guarantee reliable and consistent products. This requires a good understanding of the main physical mechanisms that affect the solidification, in particular the thermodynamic description and its coupling to the transport processes of heat and mass that take place. The continuum modeling is reviewed and methods for handling the thermodynamics component of multi-element alloys are proposed. Savings in data-storage and computing costs on the order of 100 or more appear possible, when a combination of data-reduction and data-representation methods is used. To test the new approach a simplified model was proposed and shown to qualitatively capture the evolving solidification front

Overdracht van cadmium vanuit diervoeders naar melk, bloed, vlees en organen van melkkoeien

In verband met het opstellen van een proefplan voor overdrachtsonderzoek met cadmium bij lacterende melkkoeien is een inventarisatie gemaakt van het voorkomen van cadmium in dierlijke produkten van weidende- en op stal gehuisveste melkkoeien die cadmium in oplosbare vorm of via haven- en rioolslib toegediend kregen

Overdrachtsonderzoek van cadmium, lood, kwik en arseen vanuit diervoeders waaraan oplosbare verbindingen, havenslib of rioolslib zijn/is toegevoegd, naar dierlijke produkten van vleesstieren (IVVO-RIKILT proefplan C/D)

Onderzoek naar de overdracht van zware metalen en spoorelementen van diervoeders naar dierlijke produkten

The filtering analog of the variational multiscale method in large-eddy simulation

The variational multiscale method introduced by Hughes et al. [Comput. Visual. Sci. 3, 47 (2000)] is extended to the classic filtering approach in large-eddy simulation. The role of the Germano identity in the formulation is precisely indicated. Multiscale methods based on standard eddy-viscosity models are related to (anisotropic) hyperviscosity models under certain conditions. Several models are tested and found to be as accurate as the standard dynamic model, while the implementations are more simple. Finally, the turbulent stress tensor is reformulated, such that filter and derivative in the filtered equations can be treated as a single operator

Statistics of spatial derivatives of velocity and pressure in turbulent channel flow

Statistical profiles of the first- and second-order spatial derivatives of velocity and pressure are reported for turbulent channel flow at Re τ = 590. The statistics were extracted from a high-resolution direct numerical simulation. To quantify the anisotropic behavior of fine-scale structures, the variances of the derivatives are compared with the theoretical values for isotropic turbulence. It is shown that appropriate combinations of first- and second-order velocity derivatives lead to (directional) viscous length scales without explicit occurrence of the viscosity in the definitions. To quantify the non-Gaussian and intermittent behavior of fine-scale structures, higher-order moments and probability density functions of spatial derivatives are reported. Absolute skewnesses and flatnesses of several spatial derivatives display high peaks in the near wall region. In the logarithmic and central regions of the channel flow, all first-order derivatives appear to be significantly more intermittent than in isotropic turbulence at the same Taylor Reynolds number. Since the nine variances of first-order velocity derivatives are the distinct elements of the turbulence dissipation, the budgets of these nine variances are shown, together with the budget of the turbulence dissipation. The comparison of the budgets in the near-wall region indicates that the normal derivative of the fluctuating streamwise velocity (∂u ′/∂y) plays a more important role than other components of the fluctuating velocity gradient. The small-scale generation term formed by triple correlations of fluctuations of first-order velocity derivatives is analyzed. A typical mechanism of small-scale generation near the wall (around y + = 1), the intensification of positive ∂u ′/∂y by local strain fluctuation (compression in normal and stretching in spanwise direction), is illustrated and discussed