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Fluid Mechanics and Rheology of Dense Suspensions

# Fluid Mechanics and Rheology of Dense Suspensions - Fluid...

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Unformatted text preview: Fluid Mechanics and Rheology of Dense Suspensions Martin Bijou Background We consider suspensions of solid particles in a viscous liquid, Examples are everywhere, like blood,paint and industrial waste slurries This study focused on hard particles suspended densely in a Newtonian Fluid NavierStokes equations are used. What is Rheology? The study of the deformation and flow of matter under the infuence of applied stress Also called NonNewtonian Fluid Mechanics Dimensional Analysis What is the general form of The Conservation of linear momentum? Reads "density times material derivative equals density times the force of gravity plus the gradient times pi (total stress tensor). V is the velocity Suspension Viscosity There is a lot of data on viscosity and shear rate. We observe shearthickening behavior with concentrated solutions Some data from simulations says you can get the stress and shear rate for each individual particle Also, you can get the total stress on the system When is the behavior Newtonian? All suspensions are Newtonian except for yield stress behavior of very dense suspensions With increasing shear rate, there is a Newtonian Plateau and finally a steep shearthickening region Relative Viscosity vs. Shear Rate What did the graph tell us? It was a picture of the work being done on the fluid. Useful because we now see a picture of NonNewtonian viscosity vs shear rate curves A Newtonian Plateau is reached Many configurations NonNewtonian Rheology It is now widely accepted that for suspensions of spherical particles, Non Newtonian behavior is due to a system having microstructure changes under shear. Many configurations are possible Suspension Mechanics = - po I + 2no + p Po is the isotropic suspending fluid pressure No= Viscosity of Newtonian suspended fluid p=stress contribution This is the entire stress tensor Conclusions What are the aspects of suspension rheology? They are viscosity correlations, Normal stress behavior Particle migration Considering the microstucture is helpful Acknowledgements Jonathan J. Stickel Robert L. Powell UC Davis Drew Blumberg ...
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