Guillaume Ovarlez
University of Bordeaux
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Rheologica Acta | 2017
Philippe Coussot; Alexander Ya. Malkin; Guillaume Ovarlez
This issue ofRheologica Acta is devoted to the centenary of the first publication of the newly nascent science—rheology. This was a paper of E.C. Bingham (1916) “An investigation of the laws of plastic flow”, Bull US Bur Stand 13:309–353. Well, but what about earlier works demonstrating rheological effects—W. Weber (1841), F. Kohlrausch (1863), Lord Kelvin (1865) speaking about “viscosity of solids,” J.K. Maxwell (1867), with the concept of relaxation, O.E. Meyer (1874), L Boltzmann (1874) with the principle of superposition, W. Voigt (1884), T. Schwedoff (1890) and some others? Yes, there were a lot of interesting observations and even general concepts, but a push was needed or a jump of some kind to give rise to numerous, significant, and continuous developments in a new consistent field. Once, Mark Twain said: “How lucky Adam was. He knew when he said a good thing, nobody had said it before.” This is true for science too. It seemsthatsuchajump(calledtheconceptof theyieldstress) was given byE.Bingham. It happened a century ago and—quite conventionally—it is thought as the birthday of rheology. The frequency of using of “yield stress” and/or viscoplasticity is quite comparable with such fundamental terms as viscosity and elasticity. Thousands of publications concerned yielding of various materials for this century and the flood of studies related to this concept does not dry out, meaning that Bingham’s concept continues to live and be in demand. Meanwhile, one concept (yielding) was not enough for creating a new science. So, further steps were needed and they have been made. The second fundamental concept was time effects, either as thixotropy or visco-elasticity. And finally, the concept of finite deformations and non-linearity finalized the main structure components of rheology. Now, the concept of yielding should be considered in the frames of the more general theoretical structures and included as a part of the other basic ideas making up the body of modern rheology. Indeed, recent years have brought new results, novel ideas, and doubts. Is there “the” yield stress or something different? “The yield stress myth?” or reality. All rheologists repeat as an incantation that “everything flows” (παντα ρει), but since the discovery of “viscosity bifurcation” 15 years ago, most people now consider that the yield stress marks a limit between the existence of steady-state flows—above the yield stress—and the observation of continuously slowed down
Archive | 2019
Guillaume Ovarlez
This chapter deals with the rheological properties of viscoplastic suspensions. In Sect. 2, we discuss the theoretical behavior of suspensions of rigid particles in linear and nonlinear media. In Sect. 3, we present appropriate model systems, experimental setups and methods. The main experimental observations are presented in Sect. 4: we present the evolution of the elastic, plastic, and flow properties with the particle volume fraction, and we discuss the emergence of a shear-dependent microstructure. Finally, shear-induced migration and its link with normal stress differences are briefly discussed in Sect. 5.
Archive | 2019
Guillaume Ovarlez
This chapter deals with experimental methods for the measurement of the rheological properties of materials, with a focus on yield stress fluids. Section 2 provides the basis of rheometry. Standard equations for viscosimetric flows are given and their application to visco-plastic fluids is discussed. The third section deals with the measurements of the main properties of simple yield stress fluids: solid viscoelastic properties, yield stress, and visco-plastic properties. The fourth section is devoted to the measurements of the properties of thixotropic yield stress fluids, with a focus on the dependence of their behaviour on shear history and on their aging at rest. The phenomena of shear localisation and shear banding are finally discussed in the fifth section, together with possible material inhomogeneities.
Physical Review Fluids | 2017
Yasaman Madraki; Sarah Hormozi; Guillaume Ovarlez; Elisabeth Guazzelli
Journal of Non-newtonian Fluid Mechanics | 2018
Mohammadhossein Firouznia; Bloen Metzger; Guillaume Ovarlez; Sarah Hormozi
Journal of Non-newtonian Fluid Mechanics | 2018
Hassan Fahs; Guillaume Ovarlez; Xavier Chateau
XVIth International Congress on Rheology, IC | 2012
Jalila Boujlel; Mathilde Maillard; Guillaume Ovarlez; Anke Lindner; Xavier Chateau; Philippe Coussot
Rhéologie et Génie des Procédés et des Produits | 2010
Guillaume Ovarlez; Philippe Coussot
3rd Southern African Conference on Rheology | 2010
Thai-Son Vu; Guillaume Ovarlez; Xavier Chateau
XVIIEMES RENCONTRES UNIVERSITAIRES DE GENIE CIVIL : AUGC 2009 | 2009
Thai Son Vu; Fabien Mahaut; Guillaume Ovarlez; Xavier Chateau