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Author index ►Blaise Nsom, Noureddine Latrache

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Measurement of Drag Reduction in Dilute Polymer Solution using Triboelectric Effect

Appl. Rheol.28:2 (2018) 25922 (9 pages) ►

In this paper, we present a novel method we have developed for measuring the drag reduction in a dilute polymer solution, based on the triboelectricity phenomenon. The presence of a small quantity of polymer with high molecular density in a liquid decreases the friction of the liquid on solid walls. This property defines drag reduction. The friction itself produces electricity in the liquid known as triboelectricity. In this work, we show that drag reduction can be measured by measuring the triboelectric voltage in the solvent and in the polymer solution. The method was tested on well characterized dilute solution of polyethylene oxide (PEO) and the results obtained agree qualitatively well with those available in the literature, notably showing that for given flow rate, drag reduction by PEO increases with polymer concentration until reaching a plateau. Also, for given concentration, drag reduction increases with flow rate in the range of concentration and flow rate tested. More generally, a similar behavior is expected for any polymer solution obeying the power-law rheological model.► Cite this publication as follows:

Nsom B, Latrache N: Measurement of Drag Reduction in Dilute Polymer Solution using Triboelectric Effect, Appl. Rheol. 28 (2018) 25922.

We present an experimental study of the stability of the Taylor-Dean flow of well characterized suspensions of solid disks occurring between two horizontal coaxial cylinders. The inner cylinder is rotating and the outer cylinder is at rest. By means of a visualization technique, we determine the shape of the vortices which take place in the flow at the onset of the instability and the corresponding critical parameters against the flake concentration and the system aspect ratio.► Cite this publication as follows:

Daimallah A, Bouabdallah A, Nsom B, Adnane M, Alemany A: Onset of Instabilities in Taylor-Dean Flow of Yield-Stress Fluid, Appl. Rheol. 19 (2009) 33960.

The main characteristics of geological flows such as debris flows, avalanches and lahars is due to the relative importance of viscous versus inertial forces in the momentum balance.This paper considers the motion generated by the collapse of a damretaining mud, itself modeled as a power-law fluid. The equation of motion is derived in a non-dimensional form and solved analytically with the shallow-water assumption in a dry and smooth horizontal channel. Notably indicated are flow regimes and the effect of the reservoir length as well as the effect of mud rheology on flow development. Then, a parametric study of this model is produced and the effect of mud shear-thinning on flow development is pointed out.► Cite this publication as follows:

Nsom B, Ravelo B, Ndong W: Flow regimes in viscous horizontal dam-break flow of clayous mud, Appl. Rheol. 18 (2008) 43577.

This paper presents a characterization of the following dry granular materials: soya, colza and rye seeds. The physical properties of the grains and the materials are useful for characterizing the materialsÂ’ behaviour during flow, while the external conditions (consolidation) determine storage and handling conditions. The physical properties of the grains (specific densities) and of the materials as a whole (compacity or porosity, and critical angles) were measured. The flow functions were determined by modified shear box testing. Then the internal friction angles and the flowability index for each granular material were obtained. Indeed, the behaviour of a flowing granular material results from these two groups of factors and is characterized by the flowability, which is the ratio of highest consolidation stress and unconfined yield strength. In practice, the flowability index is used to classify materials, so that the larger the flowability index, the smaller the bulk solids strength will be in relation to the consolidation stress, and therefore the higher the flowability of the bulk solid.► Cite this publication as follows:

Degouet C, Nsom B, Lolive E, Grohens A: Characterization of wood granules, soya, colza and rye seeds, Appl. Rheol. 17 (2007) 36546.

► Cite this publication as follows:

Nsom B: The dam break problem for a hyperconcentrated suspension, Appl. Rheol. 10 (2000) 224.

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