scholarly journals Unified constitutive model for granular-fluid mixture in quasi-static and dense flow regimes

2021 ◽  
Author(s):  
Xiaogang Guo ◽  
Chong ◽  
Wei Wu ◽  
Yongqi Wang
Keyword(s):  
Constitutive Model ◽  
Model Development ◽  
Granular Flows ◽  
Fluid Flows ◽  
Flow Regimes ◽  
Unified Model ◽  
Fluid Mixture ◽  
Dense Flow ◽  
Static Regime ◽  
Granular Fluid

Most granular materials encountered in nature and industry lie either in the quasi-static regime or the intermediate dense flow regime. Debris materials are a typical granular material with viscous interstitial fluid, and shows solid-like behaviors before failure and fluid-like behaviors after failure. Based on Bagnold’s pioneering work on granular-fluid flows, we propose a framework for constitutive model development, which has an additive form. Based on this framework, a unified constitutive model for granular-fluid material in the quasi-static and dense flow regimes is developed. The main intergranular interactions and granular-fluid interactions controlling the mechanical behaviors are taken into account using the Mohr-Coulomb model and a Bagnold-type relation. Dry granular flows in three simple configurations, i.e., plain shear, vertical chute flow and flow on an inclined plane, are studied. Analytical solutions based on the presented unified model are obtained. Comparisons between results from the presented model and the mu(I) model indicate that the explicit partition of frictional and collisional stress components provides insights in dense granular flows. In addition, the new model is used to predict the stress-strain relations in two annular shear tests. The applicability and advantages of the unified model are discussed.

A Model Constraint for Polydisperse Solids in Multifluid Flows

2015 ◽  
Vol 137 (11) ◽  
Author(s):  
Michael P. Kinzel ◽  
Leonard Joel Peltier ◽  
Brigette Rosendall ◽  
Mallory Elbert ◽  
Andri Rizhakov ◽  
...  
Keyword(s):  
Model Development ◽  
Fluid Flows ◽  
Momentum Exchange ◽  
Carrier Fluid ◽  
Single Carrier ◽  
Cfd Models ◽  
Model Constraint ◽  
Level Model ◽  
Consistency Constraint ◽  
Multiphase Fluid

A method to assess computational fluid dynamics (CFD) models for polydisperse granular solids in a multifluid flow is developed. The proposed method evaluates a consistency constraint, or a condition that an Eulerian multiphase solution for a monodisperse material in a single carrier fluid is invariant to an arbitrary decomposition into a pseudo-polydisperse mixture of multiple, identical fluid phases. The intent of this condition is to develop tests to assist model development and testing for multiphase fluid flows. When applied to two common momentum exchange models, the constraint highlights model failures for polydisperse solids interacting with a multifluid flow. It is found that when inconsistency occurs at the algebraic level, model failure clearly extends to application. When the models are reformulated to satisfy the consistency constraint, simple tests and application-scale simulations no longer display consistency failure.

scholarly journals Using a virtual machine environment for developing, testing, and training for the UM-UKCA composition-climate model, using Unified Model version 10.9 and above

2018 ◽  
Vol 11 (9) ◽  
pp. 3647-3657 ◽  
Author(s):  
Nathan Luke Abraham ◽  
Alexander T. Archibald ◽  
Paul Cresswell ◽  
Sam Cusworth ◽  
Mohit Dalvi ◽  
...  
Keyword(s):  
Virtual Machine ◽  
Climate Model ◽  
State Of The Art ◽  
Model Development ◽  
Unified Model ◽  
Model Version ◽  
Weather And Climate ◽  
Interactive Composition ◽  
Comprehensive Test ◽  
And Training

Abstract. The Met Office Unified Model (UM) is a state-of-the-art weather and climate model that is used operationally worldwide. UKCA is the chemistry and aerosol sub model of the UM that enables interactive composition and physical atmosphere interactions, but which adds an additional 120 000 lines of code to the model. Ensuring that the UM code and UM-UKCA (the UM running with interactive chemistry and aerosols) is well tested is thus essential. While a comprehensive test harness is in place at the Met Office and partner sites to aid in development, this is not available to many UM users. Recently, the Met Office have made available a virtual machine environment that can be used to run the UM on a desktop or laptop PC. Here we describe the development of a UM-UKCA configuration that is able to run within this virtual machine while only needing 6 GB of memory, before discussing the applications of this system for model development, testing, and training.

Steady inclined flows of granular-fluid mixtures

2009 ◽  
Vol 641 ◽  
pp. 359-387 ◽  
Author(s):  
D. BERZI ◽  
J. T. JENKINS
Keyword(s):  
Volume Flow ◽  
Angle Of Repose ◽  
Recent Theory ◽  
Fluid Mixture ◽  
Flow Rates ◽  
Fluid Mixtures ◽  
Gravity Driven ◽  
Granular Fluid ◽  
Gravity Driven Flow ◽  
Inclined Flow

We extend a recent theory for steady uniform gravity-driven flow of a highly concentrated granular-fluid mixture over an erodible bed between frictional sidewalls. We first include angles of inclination greater than the angle of repose of the particles; then, we introduce a boundary condition for flow over a rigid bumpy bed. We compare the predictions of the resulting theory with the volume flow rates, depths and angles of inclination measured in the experiments on dry and variously saturated flows over rigid and erodible boundaries. Finally, we employ the resulting theory, with the assumption that the flow is shallow, to solve, in an approximate way, for the variation of height and average velocities along a steady non-uniform inclined flow of a granular-fluid mixture that moves over a rigid bumpy bed. The solutions exhibit features of the flow seen in the experiments – for example, a dry bulbous snout in advance of the fluid, whose length increases with increasing number of the particles and that disappears with increasing velocity – for which satisfactory explanations were lacking.

scholarly journals FLOW RESISTANCE DUE TO INTENSE BEDLOAD TRANSPORT

1984 ◽  
Vol 1 (19) ◽  
pp. 89
Author(s):  
Daniel M. Hanes
Keyword(s):  
Flow Resistance ◽  
Fluid Motion ◽  
Fixed Bed ◽  
Fluid Flows ◽  
Frictional Resistance ◽  
Bedload Transport ◽  
Local Pressure ◽  
Gradient Forces ◽  
Granular Fluid ◽  
Lift Off

When water flows over a stationary bed the fluid motion is retarded by both skin the friction and local pressure gradient forces related to the roughness of the bed. If the bed itself is composed of discreet movable grains, the boundary is less clearly defined and the dynamics poorly understood (see Gust and Southard, 1983). Owen (1964) proposed that saltating grains (grains which lift off the bed, move through the fluid, and fall back to the bed without colliding with other grains) have the effect of increasing the frictional resistance of the bottom. At higher flow stages, Hanes and Bowen (1984) have suggested a model for bedload transport which is based upon the dynamics of collisional grain flows following Bagnold (1954, 1956). In such a collision dominated flow, it appears that the resistance of the bed to the overlying flow can be less than the resistance of a fixed bed to the same overlying flow. This result is consistent with the dynamics of rapid granular-fluid flows, as will be discussed below.

scholarly journals Fatigue–Creep Interaction of P92 Steel and Modified Constitutive Modelling for Simulation of the Responses

Metals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 307
Author(s):  
Tianyu Zhang ◽  
Xiaowei Wang ◽  
Wei Zhang ◽  
Tasnim Hassan ◽  
Jianming Gong
Keyword(s):  
Fatigue Life ◽  
Constitutive Model ◽  
Dwell Time ◽  
Kinematic Hardening ◽  
Model Development ◽  
Strain Range ◽  
Peak Stress ◽  
Constitutive Modelling ◽  
P92 Steel ◽  
Static Recovery

Fatigue–creep interaction (FCI) responses of P92 steel are investigated experimentally and numerically. A series of isothermal FCI experiments with tensile dwell time ranging from 60 to 600 s were conducted at two temperatures under strain-controlled trapezoidal waveform. The experimental responses demonstrate that the peak stress is influenced by temperature and dwell time. In other words, creep-mechanism-influenced stress relaxation during dwell time influences the peak stress and fatigue life (Nf). In addition, effects of strain range on peak stress and fatigue life under fatigue–creep loading are evaluated. Towards developing a simulation-based design methodology for high temperature components, first a conventional unified constitutive model is evaluated against the P92 steel experimental responses. Based on the simulation deficiency of the conventional model, a modified static recovery term incorporated in the kinematic hardening rule is proposed and satisfactory simulations of the P92 steel FCI responses are demonstrated. The experimental responses of P92 steel and strengths and deficiencies of the conventional and modified Chaboche models are elaborated identifying the important FCI phenomena and progress in constitutive model development for FCI response simulation.

Constitutive model development of fetal membrane mechanics: Mechanical testing and numerical simulation

2005 ◽  
Vol 193 (6) ◽  
pp. S112
Author(s):  
Michael House ◽  
Thibault Prevost ◽  
Ming Dao ◽  
Hidemi Kato ◽  
Michelle Oyen ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Constitutive Model ◽  
Mechanical Testing ◽  
Model Development ◽  
Fetal Membrane ◽  
Membrane Mechanics
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