Suspensions of particles and bubbles in yield stress fluids
Event details
| Date | 29.04.2016 |
| Hour | 12:15 › 13:15 |
| Speaker | Dr Guillaume Ovarlez, Senior Research Scientist at LOF-CNRS-Solvay-University of Bordeaux, France |
| Location | |
| Category | Conferences - Seminars |
Many dense suspensions involved in industrial processes (concrete casting, drilling muds, foodstuff transport, etc.) and natural phenomena (debris-flows, lava flows, etc.) are yield stress fluids which contain a significant fraction of coarse rigid particles. In addition, some of these materials contain air bubbles: crystal bearing magmas, aerated food emulsions, foamed plaster slurries… When scale separation between the paste microstructure (the colloidal particle size) and the noncolloidal particles or bubbles in suspension is possible, a simplification occurs: these materials can be considered as noncolloidal particles or bubbles embedded in a yield stress fluid (the colloidal paste). From a fundamental point of view, one then deals with suspensions in which particles interact through nonlinear hydrodynamical interactions.
In this talk, we will present recent advances in the characterization and understanding of the behavior of suspensions of rigid and soft inclusions in yield stress fluids.
We will first show how model materials and appropriate procedures are designed to focus on the purely mechanical contribution of the particles/bubbles to the yield stress fluid behavior, independently of the physicochemical properties of the materials. This allows an in depth comparison with micromechanical estimates. We will then focus on the impact of particles on the linear and nonlinear rheological properties (elastic modulus, yield stress, consistency) of the fluid. The variations of these properties with the particle volume fraction are found to be in good agreement with those predicted by a micromechanical approach in which the concentration of shear between the inclusions is taken into account. In the case of suspensions of bubbles, bubbles can behave as rigid or soft particles, dependant on their physical properties and on the interstitial fluid mechanical properties; we will show that the visco-elastic and visco-plastic behaviors of these materials are governed by two different dimensionless capillary numbers, which gives rise to original properties.
We will finally briefly discuss shear-induced migration and shear-induced sedimentation issues. These phenomena can be quantitatively modeled when the 3D behavior of the interstitial yield stress fluid and the local properties of shear between the particles are taken into account.
References:
1. F. Mahaut, X. Chateau, P. Coussot, G. Ovarlez, Yield stress and elastic modulus of suspensions of noncolloidal particles in yield stress fluids, Journal of Rheology 52, 287-313 (2008).
2. X. Chateau, G Ovarlez, K. Luu Trung, Homogenization approach to the behavior of suspensions of noncolloidal particles in yield stress fluids, Journal of Rheology 52, 489-506 (2008).
3. T.-S. Vu, G. Ovarlez, X. Chateau, Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids, Journal of Rheology 54, 815-833 (2010).
4. G. Ovarlez, F. Bertrand, P. Coussot, X. Chateau, Shear-induced sedimentation in yield stress fluids, Journal of Non-Newtonian Fluid Mechanics 42, 148-157 (2012).
5. L. Ducloué, O. Pitois, J. Goyon, X. Chateau, G. Ovarlez, Coupling of elasticity to capillarity in soft aerated materials, Soft Matter 10, 5093-5098 (2014).
6. L. Ducloué, O. Pitois, J. Goyon, X. Chateau, G. Ovarlez, Rheological behaviour of suspensions of bubbles in yield stress fluids, Journal of Non-Newtonian Fluid Mechanics 215, 31-39 (2015).
7. G. Ovarlez, F. Mahaut, S. Deboeuf, N. Lenoir, S. Hormozi, X. Chateau, Flows of suspensions of particles in yield stress fluids, Journal of Rheology (2015).
Bio :
Dr Guillaume Ovarlez is senior research scientist (Directeur de Recherche) at CNRS Laboratory Of the Future in Bordeaux, France since 2014. He previously was a CNRS senior researcher at Laboratoire Navier, Ecole des Ponts since 2003. He holds a PhD in Physics from University Paris XI and an engineering degree from Ecole Polytechnique, France. Dr Ovarlez has notably received the Bronze Medal of CNRS in 2009, and the prix “de la Recherche” in 2007 for his work on rheology of complex suspensions.
In this talk, we will present recent advances in the characterization and understanding of the behavior of suspensions of rigid and soft inclusions in yield stress fluids.
We will first show how model materials and appropriate procedures are designed to focus on the purely mechanical contribution of the particles/bubbles to the yield stress fluid behavior, independently of the physicochemical properties of the materials. This allows an in depth comparison with micromechanical estimates. We will then focus on the impact of particles on the linear and nonlinear rheological properties (elastic modulus, yield stress, consistency) of the fluid. The variations of these properties with the particle volume fraction are found to be in good agreement with those predicted by a micromechanical approach in which the concentration of shear between the inclusions is taken into account. In the case of suspensions of bubbles, bubbles can behave as rigid or soft particles, dependant on their physical properties and on the interstitial fluid mechanical properties; we will show that the visco-elastic and visco-plastic behaviors of these materials are governed by two different dimensionless capillary numbers, which gives rise to original properties.
We will finally briefly discuss shear-induced migration and shear-induced sedimentation issues. These phenomena can be quantitatively modeled when the 3D behavior of the interstitial yield stress fluid and the local properties of shear between the particles are taken into account.
References:
1. F. Mahaut, X. Chateau, P. Coussot, G. Ovarlez, Yield stress and elastic modulus of suspensions of noncolloidal particles in yield stress fluids, Journal of Rheology 52, 287-313 (2008).
2. X. Chateau, G Ovarlez, K. Luu Trung, Homogenization approach to the behavior of suspensions of noncolloidal particles in yield stress fluids, Journal of Rheology 52, 489-506 (2008).
3. T.-S. Vu, G. Ovarlez, X. Chateau, Macroscopic behavior of bidisperse suspensions of noncolloidal particles in yield stress fluids, Journal of Rheology 54, 815-833 (2010).
4. G. Ovarlez, F. Bertrand, P. Coussot, X. Chateau, Shear-induced sedimentation in yield stress fluids, Journal of Non-Newtonian Fluid Mechanics 42, 148-157 (2012).
5. L. Ducloué, O. Pitois, J. Goyon, X. Chateau, G. Ovarlez, Coupling of elasticity to capillarity in soft aerated materials, Soft Matter 10, 5093-5098 (2014).
6. L. Ducloué, O. Pitois, J. Goyon, X. Chateau, G. Ovarlez, Rheological behaviour of suspensions of bubbles in yield stress fluids, Journal of Non-Newtonian Fluid Mechanics 215, 31-39 (2015).
7. G. Ovarlez, F. Mahaut, S. Deboeuf, N. Lenoir, S. Hormozi, X. Chateau, Flows of suspensions of particles in yield stress fluids, Journal of Rheology (2015).
Bio :
Dr Guillaume Ovarlez is senior research scientist (Directeur de Recherche) at CNRS Laboratory Of the Future in Bordeaux, France since 2014. He previously was a CNRS senior researcher at Laboratoire Navier, Ecole des Ponts since 2003. He holds a PhD in Physics from University Paris XI and an engineering degree from Ecole Polytechnique, France. Dr Ovarlez has notably received the Bronze Medal of CNRS in 2009, and the prix “de la Recherche” in 2007 for his work on rheology of complex suspensions.
Practical information
- General public
- Free
Organizer
- Prof. Dr Brice Lecampion & Prof. Dr Katrin Beyer
Contact
- Prof. Dr Brice Lecampion