Real-time rheological investigation of complex behaviour in cornstarch suspensions

Date of award 2022.Cornstarch suspensions are well known for their surprising property of being able to support a person running across the surface of a pool of the suspension — a phenomenon called shear jamming. This phenomenon has far reaching importance across industries involving granular and colloidal solids transport. In this thesis, the design of a novel custom rheometer for the investigation of these suspensions is described. The results of applying the custom rheometer are shown and analysed in the context of the popular Wyart-Cates model of jamming suspensions. The work confirms the presence of unsteady behaviour in these suspensions, but only for a narrow range of particle concentrations; and of lower density than previously reported. This highlights some of the weaknesses of the WC model, especially as applied to suspensions of polydisperse anisometric particles such as cornstarch (deviating from monodisperse hard spheres).Cornstarch suspensions are well known for their surprising property of being able to support a person running across the surface of a pool of the suspension — a phenomenon called shear jamming. This phenomenon has far reaching importance across industries involving granular and colloidal solids transport. In this thesis, the design of a novel custom rheometer for the investigation of these suspensions is described. The results of applying the custom rheometer are shown and analysed in the context of the popular Wyart-Cates model of jamming suspensions. The work confirms the presence of unsteady behaviour in these suspensions, but only for a narrow range of particle concentrations; and of lower density than previously reported. This highlights some of the weaknesses of the WC model, especially as applied to suspensions of polydisperse anisometric particles such as cornstarch (deviating from monodisperse hard spheres)