scholarly journals Continuum Modeling of Granular Media

2014 ◽  
Vol 66 (5) ◽  
Author(s):  
J. D. Goddard
Keyword(s):  
Granular Flow ◽  
Granular Media ◽  
Evolution Equations ◽  
Particle Migration ◽  
Internal Variables ◽  
Continuum Modeling ◽  
Material Instability ◽  
Rapid Flow ◽  
Internal Balance

This is a survey of the interesting phenomenology and the prominent regimes of granular flow, followed by a unified mathematical synthesis of continuum modeling. The unification is achieved by means of “parametric” viscoelasticity and hypoplasticity based on elastic and inelastic potentials. Fully nonlinear, anisotropic viscoelastoplastic models are achieved by expressing potentials as functions of the joint isotropic invariants of kinematic and structural tensors. These take on the role of evolutionary parameters or “internal variables,” whose evolution equations are derived from the internal balance of generalized forces. The resulting continuum models encompass most of the mechanical constitutive equations currently employed for granular media. Moreover, these models are readily modified to include Cosserat and other multipolar effects. Several outstanding questions are identified as to the contribution of parameter evolution to dissipation; the distinction between quasielastic and inelastic models of material instability; and the role of multipolar effects in material instability, dense rapid flow, and particle migration phenomena.

Material Instability in Rapid Granular Shear Flow

2000 ◽  
Vol 627 ◽  
Author(s):  
J. D. Goddard
Keyword(s):  
Shear Flow ◽  
Granular Flow ◽  
Granular Media ◽  
Constitutive Models ◽  
Theoretical Work ◽  
Temperature Fields ◽  
Viscous Liquids ◽  
Material Instability ◽  
Recent Theoretical Work ◽  
Gas Kinetic Theory

ABSTRACTThis is a survey of recent theoretical work on shear flow instabilities of dry granular media in the Bagnold or “grain-inertia” régime. Attention is devoted to steady homogeneous unbounded simple shear, with the goal of identifying material (constitutive) instabilities arising from the coupling of stress to granular concentration and temperature fields. Such instabilities, the dissipative analogs of thermodynamic phase transitions, are familiar in numerous branches of the mechanics of materials.The current interest is motivated in part by the “dissipative clustering” found in various particle-dynamics (“DEM”) simulations of granular systems. Since particle clustering may invalidate standard gas kinetic theory, it is pertinent to ask whether hydrodynamic models based on such theories may themselves exhibit clustering instability.The present article is based largely on a recent review (Goddard and Alam 1999), which provides a unified linear-stability treatment for rapid granular flow, as well for slow flow of mobile particles immersed in viscous liquids. The analysis is based on a “short-memory” response of various fluxes to perturbations on steady uniform states, a feature characteristic of the most popular constitutive models for granular flow. In the absence of gravity, previous theoretical analyses reveal transverse “layering” and spanwise “corrugations” as possible forms of material instability (Alam and Nott 1998)Based on current theoretical findings, further work is recommended, including the exploration of the effects of gravity and of stress relaxation, both of which are likely to be important in real granular flows.

Role of contact couples and couple stress in the behaviour of granular media

1998 ◽  
Vol 08 (PR8) ◽  
pp. Pr8-87-Pr8-94
Author(s):  
F. Dedecker ◽  
Ph. Dubujet ◽  
B. Cambou
Keyword(s):  
Couple Stress ◽  
Granular Media

Tunnel excavation in granular media: the role of force chains

2021 ◽  
Vol 23 (4) ◽  
Author(s):  
Raj Kumar Pal ◽  
Robert Buraque de Macedo ◽  
José E Andrade
Keyword(s):  
Granular Media ◽  
Force Chains ◽  
Tunnel Excavation

scholarly journals Analysis of hydrological changes and flood increase in Niamey based on the PERSIANN-CDR satellite rainfall estimate and hydrological simulations over the 1983–2013 period

2015 ◽  
Vol 370 ◽  
pp. 117-123 ◽  
Author(s):  
C. Casse ◽  
M. Gosset
Keyword(s):  
Land Use Changes ◽  
Marked Change ◽  
Extreme Rainfall ◽  
Rapid Flow ◽  
Change In The Mean ◽  
The Mean ◽  
Satellite Rainfall ◽  
The City ◽  
Satellite Rainfall Estimate

Abstract. A dramatic increase in the frequency and intensity of floods due to the Niger River in the city of Niamey (Niger) has been observed in the last decade. Previous studies highlighted the role of the land use changes on the flood increase since 1970s. In the last decade, observations have raised the issue of a possible increase in extreme rainfall in the Sahel, which may have caused the recent and extreme floods in Niamey in 2010, 2012 and 2013. The study focuses on the 125 000 km2 basin between Ansongo and Niamey. This is the drainage area of the monsoon rainfall that leads to the rapid flow rise occurring between June and October. To understand the possible role of rainfall in flood intensification, satellite rainfall estimate is attractive in a region where the operational gauge network is sparse. This paper analyses the evolution of the Niger hydrograph in Niamey based on discharge observations, hydrological modelling and the satellite product PERSIANN-CDR, over the 1983–2013 period. PERSIANN-CDR is first compared with four other rainfall products. The salient features of the observed changes, i.e. a marked change in the mean decadal hydrograph, is well mimicked by the simulations, implying that rainfall is the first driver to the observed changes. The increase of flooded years over the period is also well reproduced but with some uncertainties in the exact number of flood days per year.

scholarly journals دور التربية الإسلامية في الإنماء الخلقي للشعب (دراسة على الإسلام ودوره في الإنماء القومي بإندونيسيا)

2017 ◽  
Vol 4 (1) ◽  
pp. 101
Author(s):  
Tabrani ZA
Keyword(s):  
National Development ◽  
Moral Values ◽  
Islamic Education ◽  
Resistance Force ◽  
Process Of Change ◽  
Rapid Flow ◽  
Life Issues ◽  
The One ◽  
Intellectual Level

<p>Islam as a religion of rahmatan li al'alamin, very much its contribution to the national development which is oriented to the whole human development. The presence of religion is always accompanied by "two faces". On the one hand, inherently religion has an identity that is exclusive, particularistic, and primordial. At the same time, however, it is also rich in inclusive, Universalist and transcending identities. In its role as a directive system, religion is placed as the main reference in the process of change. Religion will serve as a supreme morality that provides the basis and strength of the society's spiritual elite as they dialectics with change. Likewise as a defensive system, religion becomes a kind of resistance force for society when it is in an increasingly complex circle of life issues amid the rapid flow of change. Islamic education as agents of social change that is in the atmosphere of modernization and globalization today is required to be able to play its role dynamically and proactively, both at the theoretical and practical intellectual level. Islamic education is not just a process of cultivating moral values to fortify itself from the negative excesses of globalization. But the most important thing is how the moral values that have been invested in Islamic education are able to act as a liberating force from the crush of poverty, ignorance and socio-cultural and economic backwardness. This paper aims to explore the role of Islamic education in public social education which is the main foundation of a nation's development.</p>

scholarly journals Thermo-mechanical behavior of a granular media in a rotating drum

2019 ◽  
Vol 20 (2) ◽  
pp. 203
Author(s):  
Soumia Teyar ◽  
Mathieu Renouf ◽  
Yves Berthier
Keyword(s):  
Free Surface ◽  
Velocity Field ◽  
Numerical Experiment ◽  
Granular Flow ◽  
Granular Media ◽  
Free Surface Flows ◽  
Rail Transport ◽  
Rotating Drum ◽  
Electrical Behavior ◽  
Surface Flows

In the complex granular flow, the shear and flow of particles lead to increase in temperature that can enchain behavioral modifications. However, their thermo-mechanical and electrical behavior is of great interest for applications such as rail transport, grinding, and granular material reproduction systems. To study these behaviors, a numerical experiment is carried out on a rotating drum model. This device makes it possible to generate continuous and controlled free surface flows. Relying on the NSCD approach, the location of the hottest zone and the evolution of the temperature are correlated with the evolution of the velocity field.

Comparison of the μ(I) and HBP models for simulating granular media

2018 ◽  
Vol 29 (07) ◽  
pp. 1850050 ◽  
Author(s):  
Mehran Kheirkhahan ◽  
Khosrow Hosseini
Keyword(s):  
Friction Coefficient ◽  
Failure Mode ◽  
Granular Flow ◽  
Granular Media ◽  
State Equation ◽  
Dam Break ◽  
Harmonic Mean ◽  
Height Ratio ◽  
Viscoplastic Models ◽  
Applied Stresses

Application of Lagrangian meshless methods in modeling granular flow has been a major concern for researchers due to their particular nature. For modeling granular movement, it is assumed that the particles are continuous. The SPHysics code is developed for modeling the movement of Newtonian fluids in which the pressure is derived from the state equation. In this study, [Formula: see text] and Herschel–Bulkley–Papanastasiou (HBP) viscoplastic models are implemented in the SPHysics code to analyze the movement of grains induced by the applied stresses. In the first model, the movement of granular particles is based on the characteristics such as inertia and friction coefficient, and in the second model, the movement is related to the non-Newtonian viscoplastic behavior of fluids. The accuracy of the models is evaluated by simulating the experimental benchmarks for granular dam break. The effect of length-to-height ratio on the failure mode of dam break phenomenon is also investigated. The performance of the models is increased by introducing the gate removal speed and also the harmonic mean of the viscosity instead of the viscosity proper to each particle. This study shows that the models could capture the behavior of grains in the static and the dynamic parts of the mass body.

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