IMSc Webinar

Disordered systems under external drive: Application to fracture and flow

Subhadeep Roy

PoreLab, Department of Physics, Norwegian University of Science and Technology & University of Oslo

The primary importance of the study of disordered systems under external drive lies in the extreme nature of the statistics, translating into very rich relaxation dynamics. One of the practical applications explored in this regard is the study of the failure process in a disordered system, known as the fiber bundle model, acted by threshold activated dynamics. The model is explored to understand different models of failure that material goes through depending on strength of disorder, size of the system, range of stress relaxation, temperature, system size, the existence of defects like micro-cracks, etc. With a controlled variation in the above parameters, we observe processes with different modes of failure: abrupt (brittle), non-abrupt (quasi-brittle), nucleating, or random in space. A second practical application, on the other hand, will be the study of multi-phase flow that involves understanding the behavior in large-scale processes (oil recovery, CO2 sequestration, groundwater collection, etc.) by breaking down the dynamics of fluid in the pore scale. The disorder in capillary barriers at pores effectively creates a yield threshold in the porous medium that the external drive has to overcome. A dynamic pore network model is studied in this case in order to understand the effective rheology and flow equations of a multiphase flow through porous media. A transition from nonlinear rheology to a linear Darcy flow is observed with an increasing external drive (pressure gradient or flow rate) where the nonlinear region is observed to be highly influenced by various parameters like capillary threshold, pore-size distribution, saturation, wetting condition, compressibility, etc.

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