THESIS
2018
xxi, 157 pages : illustrations (some color) ; 30 cm
Abstract
A debris flow is a rapid moving mass of fluid-sediments mixtures that travels down a slope
under the influence of gravity. Both solid and fluid phases vitally influence the debris flow
dynamics. Due to high sediment concentration and mobility characteristics, debris flow can be
extremely destructive, which greatly threatens people’s life and property safety. In this
study, the behavior of fluid phase is resolved by solving the Reynolds Averaged Navier-Stokes
equation in CFD (Computational Fluid Dynamics), with the Volume of Fraction (VOF) method
to solve the water part in fluid phase, while the DEM (Discrete Element Method) is used to
simulate solid materials by particle contact model. The coupled CFD-DEM simulation
accounts for various solid and fluid interaction forces in de...[
Read more ]
A debris flow is a rapid moving mass of fluid-sediments mixtures that travels down a slope
under the influence of gravity. Both solid and fluid phases vitally influence the debris flow
dynamics. Due to high sediment concentration and mobility characteristics, debris flow can be
extremely destructive, which greatly threatens people’s life and property safety. In this
study, the behavior of fluid phase is resolved by solving the Reynolds Averaged Navier-Stokes
equation in CFD (Computational Fluid Dynamics), with the Volume of Fraction (VOF) method
to solve the water part in fluid phase, while the DEM (Discrete Element Method) is used to
simulate solid materials by particle contact model. The coupled CFD-DEM simulation
accounts for various solid and fluid interaction forces in debris flow, which consist of the
buoyancy force, drag force and virtual mass force and so on. Through some validations and
simulations, it is demonstrated that the coupled CFD-DEM model using the VOF method is an
efficient and reliable numerical tool to simulate the three-phase air-water-particle system and
study the fluid-particle interaction of the debris flow.
The Bonded Particle Model (BPM) in DEM is implemented to model the structure, so that the
failure pattern and damage of structures from debris flow impact can be studied, which help
to enhance our understanding on debris flow-structure interaction mechanism. A parallel bond
is established between two particles to model the mechanical behaviour of the brittle cement.
Validation case, including the bending of a cantilever beam, has been conducted to verify that
the bonded particle model can be used to reproduce macroscopic characteristics of the
cemented material. The comparison case of the bonded particles and unbonded particles
settling from the air into water, has been conducted to study the influence of the flow field on
different types of particles column with or without bonding, which also validates the feasibility
of implementing Bonded Particle Model in the coupled CFD-DEM method.
The rheological behaviour of a debris flow and the three-dimensional topography of its path
greatly influence the debris flow mobility and impact force on structures. Incorporation of
topography plays a crucial role in analysing the historical landslide events or predicting the
scope of influence of the possible disaster.
Post a Comment