Particles in dense suspensions give rise to a multifaceted change in flow behavior that are relevant in process and civil engineering but also play key roles in environmental processes. Prominent examples are the discontinuous shear thickening of corn starch, the destructive potential to move large boulders in debris flows, and the shear thinning of quick sand, to name just a few. Understanding the flow behavior of dense suspensions as a function of the material properties of the particles and the fluid is therefore of fundamental interest in engineering and physics.
The key challenge to understand these changes in flow behavior is to link the micromechanical interactions of the particles to the macroscopic flow behavior of the suspension. Depending on the situation and the analysis of the system, this results in an effective viscosity, which is larger than the clear fluid viscosity, often showing anisotropic behavior that is dictated by the shear rate. Such anisotropic behavior is also expressed in terms of a macroscopic friction coefficient and an effective volume fraction. As such, the rheology of a suspension plays a key role as a constitutive equation in larger scale models of engineering. The rheological behavior of a suspension is determined by a wide host of stress scales, e.g., short range lubrication and far-field viscous effects, contact and friction, particle inertia, cohesion and yield stress as well as a combination of all these stresses. Even though substantial progress has been made in recent years to understand the relevance of those different properties on the complex flow behavior of dense suspensions, a comprehensive rheological framework is still lacking, which limits the predictive capacity of the larger scale models.
Consequently, the Advanced School aims to provide an overview of the state-of-the-art research on the rheological behavior of dense suspensions from different perspective covering applications from process engineering, civil engineering and material science, as well as geophysical applications. The courses will provide a solid background in the theory of the rheology of dense suspensions and will give a broad overview of applications, for which subscale rheological processes are relevant. The lectures will cover examples from the laboratory, numerical simulations and field scale applications, where a focus will be given to imitating assumptions of the underlying modeling approach and potential to connect the different applications to a unifying framework.