On a role

Computer Aided Civil and Infrastructure Engineering

First Year – Fall ......................... .............................................................................................. Credits MAT 210 ..................................... Calculus I ............................................................................. 4.0 ENG 110...................................... Expository Writing ............................................................. 3.0 CHE 210 ...................................... Chemistry I .......................................................................... 4.0 HUM 100 OR SOC 101 OR PSY 101 ........................................................................................ 6.0 Subtotal ...................................... .............................................................................................. 17

Chemical Engineering Scienceについて

There are two types of debris flows, known as Lahar and Jökulhlaup. The word Lahar is Indonesian in origin and has to do with flows that are related to volcanic activity. A variety of factors may trigger a lahar, including melting of glacial ice due to volcanic activity, intense rainfall on loose pyroclastic material, or the outbursting of a lake that was previously dammed by pyroclastic or glacial material.

What is debris flow

Journal of Non-Newtonian Fluid Mechanics

Flexible barriers are increasingly used for the protection from debris flow in mountainous terrain due to their low cost and environmental impact. How- ever, the development of a numerical tool for the ratio- nal design of such structures is still a challenge. In this work, a hybrid computational framework is presented, using a total Lagrangian formulation of the finite element method to represent aflexible barrier. The actions exerted on the structure by a debris flow are obtained from si- multaneous simulations of the flow of a fluid-grain mix- ture, using two conveniently coupled solvers: the discrete element method governs the motion of the grains, while the free-surface non-Newtonian fluid phase is solved us- ing the lattice Boltzmann method. Simulations on real- istic geometries show the dependence of the momentum transfer on the barrier on the composition of the debris flow, challenging typical assumptions made during the design process today. In particular, we demonstrate that both grains and fluid contribute in a nonnegligible way to the momentum transfer. Moreover, we show how the flexibility of the barrier reduces its vulnerability to struc- tural collapse, and how the stress is distributed on its fabric, highlighting potential weak points.

/pdf/particle-fluid-structure-interaction-for-debris-flow-impact-4udefj1wpp.pdf

Particle–Fluid–Structure Interaction for Debris Flow Impact on Flexible Barriers

Flexible barriers are increasingly used for the protection from debris flow in mountainous terrain due to their low cost and environmental impact. However, a numerical tool for rational design of such structures is still missing. In this work, a hybrid computational framework is presented, using a total Lagrangian formulation of the Finite Element Method (FEM) to represent a flexible barrier. The actions exerted on the structure by a debris flow are obtained from simultaneous simulations of the flow of a fluid-grain mixture, using two conveniently coupled solvers: the Discrete Element Method (DEM) governs the motion of the grains, while the free-surface non-Newtonian fluid phase is solved using the Lattice-Boltzmann Method (LBM). Simulations on realistic geometries show the dependence of the momentum transfer on the barrier on the composition of the debris flow, challenging typical assumptions made during the design process today. In particular, we demonstrate that both grains and fluid contribute in a non-negligible way to the momentum transfer. Moreover, we show how the flexibility of the barrier reduces its vulnerability to structural collapse, and how the stress is distributed on its fabric, highlighting potential weak points.

/pdf/particle-fluid-structure-interaction-for-debris-flow-impact-yqvak80ixs.pdf

Particle-fluid-structure interaction for debris flow impact on flexible barriers

The complexity of the interactions between the constituent granular and liquid phases of a suspension requires an adequate treatment of the constituents themselves. A promising way for numerical simulations of such systems is given by hybrid computational frameworks. This is naturally done, when the Lagrangian description of particle dynamics of the granular phase finds a correspondence in the fluid description. In this work we employ extensions of the Lattice-Boltzmann Method for non-Newtonian rheology, free surfaces, and moving boundaries. The models allows for a full coupling of the phases, but in a simplified way. An experimental validation is given by an example of gravity driven flow of a particle suspension.

/pdf/coupled-dem-lbm-method-for-the-free-surface-simulation-of-i3n40kof52.pdf

Coupled DEM-LBM method for the free-surface simulation of heterogeneous suspensions

/pdf/coupled-dem-lbm-method-for-the-free-surface-simulation-of-tn78sspnet.pdf

A granular front emerges whenever the free-surface flow of a concentrated suspension spontaneously alters its internal structure, exhibiting a higher concentration of particles close to its front. This is a common and yet unexplained phenomenon, which is usually believed to be the result of fluid convection in combination with particle size segregation. However, suspensions composed of uniformly sized particles also develop a granular front. Within a large rotating drum, a stationary recirculating avalanche is generated. The flowing material is a mixture of a viscoplastic fluid obtained from a kaolin-water dispersion with spherical ceramic particles denser than the fluid. The goal is to mimic the composition of many common granular-fluid materials, such as fresh concrete or debris flow. In these materials, granular and fluid phases have the natural tendency to separate due to particle settling. However, through the shearing caused by the rotation of the drum, a reorganization of the phases is induced, leading to the formation of a granular front. By tuning the particle concentration and the drum velocity, it is possible to control this phenomenon. The setting is reproduced in a numerical environment, where the fluid is solved by a lattice-Boltzmann method, and the particles are explicitly represented using the discrete element method. The simulations confirm the findings of the experiments, and provide insight into the internal mechanisms. Comparing the time scale of particle settling with the one of particle recirculation, a nondimensional number is defined, and is found to be effective in predicting the formation of a granular front.

Alessandro Leonardi

Papers

Particle–Fluid–Structure Interaction for Debris Flow Impact on Flexible Barriers

Particle-fluid-structure interaction for debris flow impact on flexible barriers

Coupled DEM-LBM method for the free-surface simulation of heterogeneous suspensions

Coupled DEM-LBM method for the free-surface simulation of heterogeneous suspensions

Granular-front formation in free-surface flow of concentrated suspensions