Our Research Focus

This project takes into account mono-disperse grain and water mixture flows, in which the

grain-water interacting continua is treated as a buoyancy and Darcy drag coupled multiphase medium. The proposed depth-averaged model consists of four conservation equations describing temporal and spatial evolution of the grains and water depths as well as the associated grain and water depth-averaged velocities. It considers layered development and incorporates a shear velocity profile into the model, instead of the standard plug flow that is employed by almost all existing models of debris flows. In the under-saturated region, shear results in the surface layer of dry grains moving faster than the bulk, and they are preferentially transported to the flow front to develop a dry snout. Conversely, in the over-saturated region, the flow thickness is sufficiently small that the water friction is stronger than the friction acting on the grains. As a result, the surface grains can move faster than the water and leave it behind. The proposed theory provides a rational framework that is capable of uncovering complete longitudinal profiles of debris flows from the dry granular front to the
pure watery tail without the need to consider particle-size segregation.