Possible optimisation of pastes and the according apparatus in process engineering by MRI flow experiments

Götz, Joachim; Zick, Klaus; Kreibich, W

doi:10.1016/s0255-2701(02)00078-8

Cited by 11 publications

(1 citation statement)

References 55 publications

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“…The notion of suspension temperature was introduced by Nott & Brady (1994) in a continuum model aimed at calculating steady-state velocity and concentration profiles in flows of concentrated suspensions. In fact, velocity fluctuations lead to the migration and diffusion of particles in shear flows, phenomena that occur in a wide variety of natural as well as engineering problems, ranging from the dispersion and migration of red blood cells (Bishop et al 2002) to the food industry (Cullen et al 2000;Gotz, Zick & Kreibich 2003), hence it is important to determine their properties. In particular, we are interested in the dependence of the velocity fluctuations on the concentration and microstructure of the suspension.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and velocity fluctuations in sheared suspensions

et al. 2004

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The velocity fluctuations present in macroscopically homogeneous suspensions of neutrally buoyant, non-Brownian spheres undergoing simple shear flow, and their dependence on the microstructure developed by the suspensions, are investigated in the limit of vanishingly small Reynolds numbers using Stokesian dynamics simulations. We show that, in the dilute limit, the standard deviation of the velocity fluctuations (the so-called suspension temperature) is proportional to the volume fraction, in both the transverse and the flow directions, and that a theoretical prediction, which considers only for the hydrodynamic interactions between isolated pairs of spheres, is in good agreement with the numerical results at low concentrations. Furthermore, we show that the whole velocity autocorrelation function can be predicted, in the dilute limit, based purely in two-particle encounters. We also simulate the velocity fluctuations that would result from a random hard-sphere distribution of spheres in simple shear flow, and thereby investigate the effects of the microstructure on the velocity fluctuations. Analogous results are discussed for the fluctuations in the angular velocity of the suspended spheres. In addition, we present the probability density functions for all the linear and angular velocity compo- The simulations include a non-hydrodynamic repulsive force between the spheres which, although extremely short ranged, leads to the development of fore-aft asymmetric distributions for large enough volume fractions, if the range of that force is kept unchanged.On the other hand, we show that, although the pair distribution function recovers its fore-aft symmetry in dilute suspensions, it remains anisotropic and that this anisotropy can be accurately described by assuming the complete absence of any permanent doublets of spheres.We also present a simple correction to the analysis of laser-Doppler velocimetry measurements, that only takes into account the mean angular rotation of the spheres in the vorticity direction, and which substantially improves the interpretation of these measurements at low volume fractions.

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Section: Introductionmentioning

confidence: 99%

Microstructure and velocity fluctuations in sheared suspensions

et al. 2004

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The Principle of the Auger Extruder

Bridgwater

2009

Engineering Materials and Processes

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Ram extrusion force for a frictional plastic material: model prediction and application to cement paste

et al. 2006

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the original publication is available at http://www.springerlink.com/content/pn3034u81144458g/International audienceWe developed a model to predict the ram extrusion force of frictional plastic materials such as cement-based pastes. The extrusion of cement-based materials has already been studied, but the interaction between shaping force and paste behaviour still have to be understood. Our model is based on the plastic frictional behaviour of cement-based materials and integrates the physical mechanisms that govern material extrusion flow and extrusion force increase. When the process starts, a pressure gradient is created in the extruder due to wall friction of the paste that is submitted to plug flow. It induces a consolidation of the material. As a result, a large increase of extrusion force appears. A Coulomb law is used to model cement-based materials, which is considered as consolidating granular media. Such modelling is compared with experimental results. Tests were carried out on extrudible cement pastes. Modelling and experimental results are in good agreement

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Possible optimisation of pastes and the according apparatus in process engineering by MRI flow experiments

Cited by 11 publications

References 55 publications

Microstructure and velocity fluctuations in sheared suspensions

Microstructure and velocity fluctuations in sheared suspensions

The Principle of the Auger Extruder

Ram extrusion force for a frictional plastic material: model prediction and application to cement paste

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