Title: The origin of resistive force theory in granular materials

Author (Talk): Hesam Askari, MIT

Abstract:

The interaction of loose terrain with solid objects produces complex dynamics in animal and vehicle locomotion, and in geotechnical and aerospace applications. The granular Resistive Force Theory (RFT) is a recently proposed empirical method to determine force distributions caused by such interactions. Its remarkable effectiveness and simplicity are surprising given the complexities of granular flow, begging fundamental questions of why RFT works. We have discovered that RFT arises solely from a frictional yield criterion, forming a link between RFT and continuum plasticity. Without any fitting, plasticity reproduces experimental RFT data, and derives RFT's foundational assumptions including spatial force superposition. Continuum dimensional analysis explains why RFT is more accurate in granular media than its older counterpart for viscous fluids, which instructs the development of RFT's in other media and for more diverse conditions.