Research Projects

Dense shear thickening suspensions of non-Brownian particles are present in a range of industrial applications and products such as cement mix, ceramic paste, fuel mix for rocket engine, chocolate refiner paste, and many more. Contrary to simple Newtonian fluids with constant viscosity, these suspensions are found to show continuous and discontinuous rise in viscosity with shear rate leading to jamming. From our present understanding, it is known that shear thickening and jamming in dense suspensions are influenced by particle size distribution and shapes of the suspended particles. A few recent studies have reported delayed shear thickening and jamming transition in dense suspensions of bi-disperse systems as compared to nearly mono-dispersed suspensions. Additionally, dense suspensions of non-spherical cubic particles are found to show stronger shear thickening than spherical particles. Thus the flowability of these suspensions can be controlled by particle shape and size distribution. However, to control the flowability, physics involved in the transition from a flowable state to a shear induced rigid jammed state should be well understood, which is currently missing. Specifically, the role of particle size distribution and particle shape on the flow microstructure near the jamming transition has not been investigated so far. In this project, we will investigate these aspects and characterize jamming transition in dense suspensions of spherical and non-spherical particles with wide polydispersity. To address our problem we will employ computational method such as LF-DEM (Lubrication Flow-Discrete Element Method) simulations on model systems and carry out rheology experiments on suspensions of PMMA (polymethyl methacrylate) and alumino silicate particles. Recently, we have performed LF-DEM simulations to characterize a critical transition preceding shear jamming phenomena in nearly-monodisperse dense suspensions of spherical particles [Santra et al., arXiv:2401.15165, 2024] and have shown the critical transition to follow 2D Ising model. Based on the understanding from our previous study we expect to define an order parameter for the polydisperse suspensions which could show a critical transition near shear jamming both computationally and in experiments. Specifically, we aim to carry out shear reversal experiments coupled with flow visualization to analyze the fluctuations in the shear viscosity, to characterize any critical phenomenon near shear jamming transition, and compare the results with simulations. Our study will be extremely useful to improve the fundamental understanding on the origin of shear jamming and the factors controlling it in shear thickening suspensions. These insights will shed some light on the dynamics of flow microstructure in dense suspensions, both near and far from jamming transition, which will be useful for designing material, consisting of particle suspensions, with controllable flow properties.