Two-Phase Approach to Modeling the Grain-Fluid Flows with Deposition and
Entrainment over Rugged Topography
Abstract
We present a grain-fluid mixture for debris flows moving on a rugged
(non-trivial) topography, where entrainment and deposition may take
place. The model equations are derived with respect to a
terrain-following coordinate system, which is constructed based on the
topographic surface. The coordinates are fixed in space, and a
“subtopography” is added on the coordinate surface to account for the
variation in the local topography when entrainment or deposition takes
place. Numerical implementation is made based on a GPU-accelerated
simulation tool, into which the entrainment-deposition mechanism is
integrated accordingly. Two numerical examples are assigned to
investigate the key features of the proposed model. One is on a
horizontal plane, on which a finite mass of grain-fluid mixture is
released from the state of rest. In this example, debris flow deposits
significantly impact the post-event} morphology and the associated flow
behaviors. The other concerns a moving mass down an inclined chute
merging into a horizontal deposition plane, where the levee formation is
reproduced. At the end, the model is validated against a debris flow
experiment to evaluate its applicability.