Forecasting granular flow on steep terrains after interacting with an array of obstacles

2021 ◽  
Author(s):  
Su Yang ◽  
Xiaoliang Wang ◽  
Qingquan Liu
Keyword(s):  
Granular Material ◽  
Structural Design ◽  
Granular Flow ◽  
Hazard Mitigation ◽  
Protective Measure ◽  
Dynamical Process ◽  
Research Results ◽  
Mountainous Regions ◽  
Obstacle Array ◽  
Averaged Model

<p>Natural disasters such as landslides dominated by granular material may cause catastrophic consequences. Therefore, the protection of human-made facilities in mountainous areas is of great significance. An effective protective measure is to install an array of obstacles upstream of the structure that needs to be protected. We need to numerically simulate the interaction between granular flow and obstacle array, and forecast the flow path and stacking position of granular flow after interacting with an array of obstacles. The constitutive behavior and structure-interaction mode of granular material differs substantially from water flow-dominated hazards (e.g., floods). We have developed a depth-averaged model that can accurately simulate the interaction between granular flow and obstacles. Numerical simulations were performed for the case of granular flow facing a large number of different obstacles arrays to produce a dynamical process of granular flow and the depth changes of fixed detection points. We obtain different obstacles arrays by changing, including but not limited to, the type, geometric size of the obstacles, and row spacing of the arrays. We found that obstacles play roles of dissipation, deflection and hindrance, on the granular flow. For some types of obstacles, such as tetrahedron, the previous two mechanisms are dominant. Our research results show that the existence of obstacle arrays can indeed protect specific areas downstream. Furthermore, we can achieve better protection effects by changing the parameters of the array. These research results help us better forecast the result of the interaction between granular flow and an array of obstacles in space, and provide guidance for the structural design and assessment for hazard mitigation in mountainous regions. These findings advance the understanding of flow structures of fast granular flow facing obstacles, which provides guidance for structural design and assessment for hazard mitigation in mountainous.</p>

scholarly journals Aerated granular flow over a horizontal rigid surface

2000 ◽  
Vol 424 ◽  
pp. 169-195 ◽  
Author(s):  
I. EAMES ◽  
M. A. GILBERTSON
Keyword(s):  
Granular Material ◽  
Point Source ◽  
Drag Force ◽  
Granular Flow ◽  
Gas Flow ◽  
Granular Flows ◽  
Angle Of Repose ◽  
Minimum Fluidization Velocity ◽  
Granular Pile ◽  
Particle Pressure

The effect of a vertical gas flow on the dynamics of a coulombic granular material moving over a horizontal rigid porous surface has been studied experimentally and theoretically. The presence of a fluidizing gas significantly alters the granular flow dynamics. When the gas velocity, ug, is below the minimum fluidization velocity, umf, the effect of the gas is to reduce the angle of repose θ from the value measured in the absence of a gas flow. When material is poured from a point source onto a horizontal surface it forms a pile, which adjusts through episodic avalanching to a self-similar conical shape. Under these conditions, the development of the pile is determined by the local force balance on individual particles and its extent may be expressed in terms of the volume of particles added and the angle of repose. A volume of material is poured continuously from a point source onto a surface according to Qtα. Below the minimum uidization velocity, a quasi-static description gives the encroachment distance of the granular pile as l = (2Q/(2π/3)n−1 tan θ)1/n+1tα/n+1 where n = 1 for a planar release and n = 2 for an axisymmetric release.A continuum description of fluidized granular flow has been developed by vertically averaging the mass and momentum conservation equations and including the momentum exchange between the gas and granular flow. The bulk movement is driven along the ground by horizontal gradients of particle pressure and is resisted by a viscous drag force due to the particles moving horizontally through a vertical gas flow. Above the minimum fluidization velocity the character of the granular flow is significantly altered and takes on fluid-like properties. The model predicts the shape of the fluidized granular pile and that the encroachment distance grows as l = λnα (Q(ug + umf) / ε)1/n+2tα+1/n+2, where ε is the void fraction in the bed and λnα is a constant. Below the conditions for fluidization (ug < umf), the pile of granular material grows quasi-statically when t > t∗, where t∗ ∼ (εn+1Qug + umf) / μ2+n (umf − ug)2+n) 1/1+n−α corresponds to the critical time when frictional forces are comparable to gradients of particle pressure and the drag force. Numerical solutions describing the granular flow are presented.Experimental observations of the shape and extent of planar and axisymmetric granular flows when α = 1 compare well with theoretical predictions for various values of particle volume flux Q, time t, and gas flow rate ug. The mathematical description of fluidized granular flows along rigid surfaces indicates a strong analogy with buoyancy-driven flows in a porous medium. This analogy permits extension of our description to include flows down slopes and the effect of internal stratification.

scholarly journals Reliability - safety set of structures

2001 ◽  
Vol 23 (4) ◽  
pp. 216-223
Author(s):  
Le Xuan Huynh ◽  
Do Van Binh
Keyword(s):  
Confidence Level ◽  
Structural Design ◽  
Load Factor ◽  
Inhomogeneous State ◽  
Numerical Examples ◽  
Research Results ◽  
Random Models ◽  
Two Factors ◽  
Material Factor ◽  
The Relationship

Based on the results of A. D. Rzanitsin and V. D. Raizer in the references of [1] and [2], this paper gives other definitions of the confidence level of subjected loads βs and the confidence level of the strength of materials βR, then studies the relationship between the load factor k, the material factor m and the safety factor n in the traditional models with the factors of βs, βR and βs in the random models in the structural design. The research results show that physical meaning of two factors of βs, βR is the same as the factors of k and m, however it gives more clearly assessments on effects of the over load state and the material inhomogeneous state of the safety working state of the structures. Since the reliability - safety set is also determined from the research results. Some numerical examples are carried out to show the relationship between these above factors. 

scholarly journals Discrete element analysis of dry granular flow impact on slit dams

Landslides ◽  
2020 ◽  
Author(s):  
Sixia Gong ◽  
Tao Zhao ◽  
Jidong Zhao ◽  
Feng Dai ◽  
Gordon G. D. Zhou
Keyword(s):  
Granular Flow ◽  
Numerical Study ◽  
Discrete Element ◽  
Trapping Efficiency ◽  
Element Analysis ◽  
Mountainous Regions ◽  
Aspect Ratios ◽  
Dry Granular Flow ◽  
Slit Dam ◽  
The Impact

Abstract Slit dam is an open-check barrier structure widely used in mountainous regions to resist the destructive impacts of granular flows. To examine the dynamics of granular flow impact on slit dams, a numerical study by discrete element method (DEM) is presented in this article. The study considers dry granular materials flowing down a flume channel and interacts with slit dams installed at the lower section of the flume. The particle shape is explicitly considered by particle clumps of various aspect ratios. The slit dams are modeled as rigid and smooth rectangular prisms uniformly spaced at in the flume. Four key stages of granular flow impact on the slit dams have been identified, namely, the frontal impact, run up, pile up, and static deposition stages. In the impact process, the kinetic energy of the granular flow is dissipated primarily by interparticle friction and damping. The trapping efficiency of the slit dams decreases exponentially with the relative post spacing, while it increases with the particle clump aspect ratio. The numerical results can provide new insights into the optimization of relative post spacing for slit dam design.

scholarly journals A two-phase two-layer model for fluidized granular flows with dilatancy effects

2016 ◽  
Vol 801 ◽  
pp. 166-221 ◽  
Author(s):  
François Bouchut ◽  
Enrique D. Fernández-Nieto ◽  
Anne Mangeney ◽  
Gladys Narbona-Reina
Keyword(s):  
Granular Material ◽  
Thin Layer ◽  
Pore Pressure ◽  
Friction Force ◽  
Excess Pore Pressure ◽  
Layer Model ◽  
Two Phase ◽  
Two Layer Model ◽  
Two Phases ◽  
Averaged Model

We propose a two-phase two-thin-layer model for fluidized debris flows that takes into account dilatancy effects, based on the closure relation proposed by Roux & Radjai (Physics of Dry Granular Media, 1998, Springer, pp. 229–236). This relation implies that the occurrence of dilation or contraction of the granular material depends on whether the solid volume fraction is respectively higher or lower than a critical value. When dilation occurs, the fluid is sucked into the granular material, the pore pressure decreases and the friction force on the granular phase increases. On the contrary, in the case of contraction, the fluid is expelled from the mixture, the pore pressure increases and the friction force diminishes. To account for this transfer of fluid into and out of the mixture, a two-layer model is proposed with a fluid layer on top of the two-phase mixture layer. Mass and momentum conservation are satisfied for the two phases, and mass and momentum are transferred between the two layers. A thin-layer approximation is used to derive average equations, with accurate asymptotic expansions. Special attention is paid to the drag friction terms that are responsible for the transfer of momentum between the two phases and for the appearance of an excess pore pressure with respect to the hydrostatic pressure. For an appropriate form of dilatancy law we obtain a depth-averaged model with a dissipative energy balance in accordance with the corresponding three-dimensional initial system.

scholarly journals Granular flow through vertical slots: analysis of a general formula

2021 ◽  
Vol 249 ◽  
pp. 03027
Author(s):  
A. Medina ◽  
D.A. Serrano ◽  
A. López-Villa ◽  
M. Pliego
Keyword(s):  
Granular Material ◽  
Mass Flow Rate ◽  
General Formula ◽  
Mass Flow ◽  
Flow Rate ◽  
Granular Flow ◽  
Gravity Driven ◽  
Flow Through ◽  
Well Data

Currently, very little is known about reliable phenomelogical correlations to estimate the gravity-driven mass flow rate, of dry non-cohesive granular material, outflowing from thin thickness slots in vertical sidewalls of rectangular silos. Here, we validate a simple and general formula that fits pretty well data published elsewhere, including the cases of vertically and horizontally elongated slots.

Material Point Method Modelling of Granular Flow in Inclined Channels

2014 ◽  
Vol 553 ◽  
pp. 501-506 ◽  
Author(s):  
Wojciech Tomasz Sołowski ◽  
Scott William Sloan
Keyword(s):  
Constitutive Model ◽  
Granular Material ◽  
Granular Flow ◽  
Numerical Technique ◽  
Material Point Method ◽  
Material Point ◽  
Point Method ◽  
Experimental Results ◽  
Inclined Channels

The material point method is a novel numerical technique which is especially well-suited to solving problems involving large or extreme deformations. This paper shows the results of the modelling of flow of granular material in inclined channels. During the calculations the granular material is approximated by a Mohr-Coulomb constitutive model. The computed flow is subsequently compared to experimental results published in the literature.

Structural Design and Analysis of a New Soil Moisture Probe

2013 ◽  
Vol 368-370 ◽  
pp. 1781-1785
Author(s):  
Jun Huang ◽  
Xiao Chu Liu ◽  
Li Yao ◽  
Hao Wang ◽  
Shuo Chun Liu
Keyword(s):  
Composite Material ◽  
Soil Moisture ◽  
Structural Design ◽  
Water Saving ◽  
Probe Method ◽  
Graphite Content ◽  
Research Results ◽  
Resistance Variation ◽  
Dry Conditions ◽  
Different Content

It presents a new structure of soil moisture probe which is designed for the solar automatic water-saving irrigation. DC two-probe method is used to measure resistivity of the new probe with different content of graphite under wet and dry conditions. The results show the resistance variation of the composite material with more than 25% graphite content is very small, its suitable for the production of two-pin probe; the conduction of composite material with less than 15% graphite content are greatly affected by the cement, its suited for the production of one-pin probe. The research results can be used as reference for choosing moisture probe according to different soil.

Structural Design of Mountain Tunnels in the 3rd Pipeline Project of Natural Gas Transmission from West to East China

2014 ◽  
Vol 1049-1050 ◽  
pp. 217-220 ◽  
Author(s):  
Xiao Jun Zhou
Keyword(s):  
Natural Gas ◽  
Structural Design ◽  
East China ◽  
Concrete Lining ◽  
Tunnel Support ◽  
Mountainous Regions ◽  
Geological Conditions ◽  
Natural Gas Transmission ◽  
Pipeline Project ◽  
Mountain Tunnels

This paper mainly summarizes the structural design of mountain tunnels used to lay natural gas pipes in the 3rd pipeline project of natural gas transmission from west to east China according to the main requirement of laying gas pipes in mountain tunnels supported with concrete lining in light of geological conditions of surrounding rock, the designed parameters for tunnel lining are presented and meanwhile, the installation of gas pipe is also illustrated in the paper. The type of laying gas pipe and designing of tunnel support in mountainous regions proposed in this paper can provide practicable guidance to the design and construction of oil and gas pipe tunnels under similar circumstances.

scholarly journals Nonlocal rheology of dense granular flow in annular shear experiments

Soft Matter ◽  
2018 ◽  
Vol 14 (16) ◽  
pp. 3040-3048 ◽  
Author(s):  
Zhu Tang ◽  
Theodore A. Brzinski ◽  
Michael Shearer ◽  
Karen E. Daniels
Keyword(s):  
Granular Material ◽  
Granular Flow ◽  
Flow Fields ◽  
Steady Shear ◽  
Experimental Measurements ◽  
Rheological Models ◽  
Dense Granular Flow

Experimental measurements of boundary stresses and flow fields of a quasi-2D granular material under steady shear validate two nonlocal rheological models.

scholarly journals Research regarding the common problems of design of the bunkers – A review

2021 ◽  
Vol 286 ◽  
pp. 03024
Author(s):  
Ancuta Alexandra Petre ◽  
Mariana Mădălina Stanciu ◽  
Dumitru Bogdan Mihalache ◽  
Dragoș Dumitru
Keyword(s):  
Granular Material ◽  
Power Supply ◽  
Granular Flow ◽  
Free Space ◽  
Solid Material ◽  
Innovative Solutions ◽  
The Common ◽  
Common Problems ◽  
Suitable Power ◽  
Considerable Damage

Understanding the behavior of granular material in a bunker not only helps to design properly and achieve the correct granular flow, but also needs the engineer to ensure that the bunker is properly designed and conducted to withstand the tasks and demands exercised during its operation. Small and shallow bunkers are commonly used in industry when free space is limited. Shallow bunkers induce the flow of the funnel, which can cause problems such as segregation and agglomeration of the material inside it, which leads to considerable damage to the final product. The design and location of a suitable power supply and an appropriate outlet is still critical and is perceived rather as a science. The paper presents some innovative solutions related to the design, modeling and construction of solid material storage and unloading bunkers.

Sign in / Sign up

Export Citation Format

Share Document