Particle-size segregation in self-channelized granular flows

Geophysical mass flows such as debris flows, dense pyroclastic and snow avalanches can self-channelize on shallow slopes. The confinement afforded by formed levees helps to maintain the flow depth, hence mobility, allowing self-channelized run out significantly farther than unconfined, spreading flows. Levee formation self-channelization are strongly associated with particle-size segregation, but also occur in monodisperse This paper uses depth-averaged theory of Rocha et al. ( J. Fluid Mech. , vol. 876, 2019, pp. 591–641), which incorporates a hysteretic friction law second-order viscous terms. Both these vital for travelling wave that progressively deposits pair just behind front. three-dimensional velocity field is reconstructed frame moving front assuming Bagnold flow. enables bidisperse segregation be used solve large small particle concentrations paths three-dimensions, first time. model shows particles tend segregate surface flow, forming carapace extends over centre channel, well along external sides base levee walls. downwards, concentrated main channel inner supports contention low-friction lining provides secondary mechanism run-out enhancement. It shown entire scales diameter, so experiments millimetre-sized provide important insights into geophysical-scale boulders smaller rock fragments. does not need occur, hypothesis frictional feedback enhance both mobility strength.