Establishment and verification of a contact model of flowing fresh concrete

Purpose The purpose of this paper is to establish a new dynamic coupled discrete-element contact model used for investigating fresh concrete with different grades and different motion states, and demonstrate its correctness and reliability according to the rheological property results of flow fresh concrete in different working states through simulating the slump process and mixing process. Design/methodology/approach To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength. The fluid-like fresh concrete is modelled as a two-phase fluid consisting of mortar and aggregate. Depending on the contact forms of the aggregate and mortar, the model is of one of the five types, namely, Hertz–Mindlin, pendular LB contact, funicular mucous contact, capillary LB contact or slurry lift/drag contact. Findings To verify the accuracy of this contact model, concrete slump and cross-vane rheometer tests are simulated using the traditional LB model and dynamic coupled contact model, for five concrete strengths. Finally, by comparing the simulation results from the two different contact models with experimental data, it is found that those from the proposed contact model are closer to the experimental data. Practical implications This contact model could be used to address issues such as (a) the mixing, transportation and pumping of fresh concrete, (b) deeper research and discussion on the influence of fresh concrete on the dynamic performance of agitated-transport vehicles, (c) the behaviour of fresh concrete in mixing tanks and (d) the abrasion of concrete pumping pipes. Originality/value To accurately express the motion and force of flowing fresh concrete in different working states from numerical analysis, a dynamic coupled discrete-element contact model is proposed for fresh concrete of varying strength.

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Numerical Study on Concrete Pumping Behavior via Local Flow Simulation with Discrete Element Method

Materials ◽

10.3390/ma12091415 ◽

2019 ◽

Vol 12 (9) ◽

pp. 1415 ◽

Cited By ~ 3

Author(s):

Yijian Zhan ◽

Jian Gong ◽

Yulin Huang ◽

Chong Shi ◽

Zibo Zuo ◽

...

Keyword(s):

Discrete Element Method ◽

Fresh Concrete ◽

Numerical Study ◽

Flow Simulation ◽

Discrete Element ◽

Local Flow ◽

Pumping System ◽

Concrete Pumping ◽

Pipe Geometry ◽

Element Method

The use of self-consolidating concrete and advanced pumping system enables efficient construction of super high-rise buildings; however, risks such as clogging or even bursting of pipeline still exist. To better understand the fresh concrete pumping mechanisms in detail, the discrete element method is employed in this paper for the numerical simulation of local pumping problems. By modeling the coarse aggregates as rigid clumps and appropriately defining the contact models, the concrete flow in representative pipeline units is well revealed. Important factors related to the pipe geometry, aggregate geometry and pumping condition were considered during a series of parametric studies. Based on the simulation results, their impact on the local pumping performance is summarized. The present work demonstrates that the discrete element simulation offers a useful way to evaluate the influence of various parameters on the pumpability of fresh concrete.

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Numerical investigation of the interaction between jet and bucket in a Pelton turbine

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1243/09576509jpe824 ◽

2009 ◽

Vol 223 (6) ◽

pp. 721-728 ◽

Cited By ~ 29

Author(s):

A Santolin ◽

G Cavazzini ◽

G Ardizzon ◽

G Pavesi

Keyword(s):

Experimental Data ◽

Numerical Analysis ◽

Detailed Analysis ◽

Numerical Investigation ◽

Two Phase ◽

Pelton Turbine ◽

Inhomogeneous Model ◽

The North ◽

Hydraulic Machines ◽

Single Jet

This article presents the numerical investigation of the interaction between the jet and the bucket in a Pelton turbine. Unsteady numerical analyses were carried out on a single jet Pelton turbine installed in the north of Italy. A two-phase inhomogeneous model was used. Two different jet configurations were analysed and compared. In the first configuration, the interaction between the runner and an axial-symmetric jet characterized by a given velocity jet profile was investigated, whereas in the second configuration the runner was coupled with the needle nozzle and the final part of the penstock and the interaction between the jet and the bucket was analysed. A detailed analysis of the torque highlighted the influence of the shape of the water jet on the turbine losses and the influence of the stator on the efficiency of this type of hydraulic machines was shown. The numerical results were compared with the experimental data derived from the installation test of the turbine in order to validate the numerical analysis.

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Modelling of ice rubble in the punch shear tests with cohesive 3D discrete element method

Engineering Computations ◽

10.1108/ec-11-2017-0436 ◽

2019 ◽

Vol 36 (2) ◽

pp. 378-399 ◽

Cited By ~ 3

Author(s):

Arto Sorsimo ◽

Jaakko Heinonen

Keyword(s):

Discrete Element Method ◽

Shear Test ◽

Discrete Element ◽

Contact Model ◽

Spherical Particles ◽

Content Type ◽

Material Parameters ◽

Simulation Results ◽

Linear Softening ◽

Element Method

PurposeThis paper aims to simulate a punch shear test of partly consolidated ice ridge keel by using a three-dimensional discrete element method. The authors model the contact forces between discrete ice blocks with Hertz–Mindlin contact model. For freeze bonds between the ice blocks, the authors apply classical linear cohesion model with few modifications. Based on punch shear test simulations, the authors are able to determine the main characteristics of an ice ridge from the material parameters of the ice and freeze bonds.Design/methodology/approachThe authors introduced a discrete model for ice that can be used for modelling of ice ridges. The authors started with short introduction to current status with ice ridge modelling. Then they introduced the model, which comprises Hertz–Mindlin contact model and freeze bond model with linear cohesion and softening. Finally, the authors presented the numerical results obtained using EDEM is commercial Discrete Element Modeling software (EDEM) and analysed the results.FindingsThe Hertz–Mindlin model with cohesive freeze bonds and linear softening is a reasonable model for ice rubble. It is trivial that the ice blocks within the ice ridge are not spherical particles, but according to results, the representation of ice blocks as spheres gave promising results. The simulation results provide information on how the properties of freeze bond affect the results of punch shear test. Thus, the simulation results can be used to approximate the freeze bonds properties within an ice ridge when experimental data are available.Research limitations/implicationsAs the exact properties of ice rubble are unknown, more research is required both in experimental and theoretical fields of ice rubble mechanics.Originality/valueBased on this numerical study, the authors are able to determine the main characteristics of an ice ridge from material parameters of ice and freeze bonds. Furthermore, the authors conclude that the model creates a promising basis for further development in other applications within ice mechanics.

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Discrete element modelling of railway ballast performance considering particle shape and rolling resistance

Railway Engineering Science ◽

10.1007/s40534-020-00216-9 ◽

2020 ◽

Vol 28 (4) ◽

pp. 382-407 ◽

Cited By ~ 1

Author(s):

Yunlong Guo ◽

Chunfa Zhao ◽

Valeri Markine ◽

Can Shi ◽

Guoqing Jing ◽

...

Keyword(s):

Shear Strength ◽

Particle Shape ◽

Large Scale ◽

Rolling Resistance ◽

Discrete Element ◽

Contact Model ◽

Discrete Element Modelling ◽

Railway Ballast ◽

Contact Models ◽

Strength And Deformation

AbstractTo simulate ballast performance accurately and efficiently, the input in discrete element models should be carefully selected, including the contact model and applied particle shape. To study the effects of the contact model and applied particle shape on the ballast performance (shear strength and deformation), the direct shear test (DST) model and the large-scale process simulation test (LPST) model were developed on the basis of two types of contact models, namely the rolling resistance linear (RRL) model and the linear contact (LC) model. Particle shapes are differentiated by clumps. A clump is a sphere assembly for one ballast particle. The results show that compared with the typical LC model, the RRL method is more efficient and realistic to predict shear strength results of ballast assemblies in DSTs. In addition, the RRL contact model can also provide accurate vertical and lateral ballast deformation under the cyclic loading in LPSTs.

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Analysis of two phase flow in liquid oxygen hybrid journal bearings for rocket engine turbopumps

Industrial Lubrication and Tribology ◽

10.1108/ilt-09-2011-0072 ◽

2014 ◽

Vol 66 (1) ◽

pp. 31-37 ◽

Cited By ~ 3

Author(s):

Zhang Guoyuan ◽

Yan Xiu-Tian

Keyword(s):

Two Phase Flow ◽

Rocket Engine ◽

Dynamic Performance ◽

Liquid Oxygen ◽

Phase Flow ◽

Vapor Mixture ◽

Two Phase ◽

Content Type ◽

Hybrid Bearing ◽

Liquid Vapor

Purpose – A hybrid bearing of advanced cryogenic rocket engine turbopump is designed. For cryogenic fluid propellants (such as liquid oxygen) as the lubrication of bearing, bearings operating close to liquid-vapor region (near the critical point or slightly sub-cooled) are likely to develop a two phase flow region. The paper aims to discuss these issues. Design/methodology/approach – In this paper, an all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented, and the general Reynolds equation and energy equation with two phase flow as lubricants is solved. The static and dynamic performance of a 50-mm-radius hybrid bearing are obtained under 20,000 rpm speed and 10 MPa supply pressure. Findings – The results show that the variations of performance of bearing operating under cryogenic liquid oxygen are not bounded by the all liquid and all vapor cases in the liquid-vapor mixture range. There behaviours are attributed to the large change in the compressibility character of the flow. Research limitations/implications – For validating the correctness of analytical model, an experimental study on the liquid-vapor nitrogen mixture lubricated hybrid journal bearings is being carried out where low-viscosity nitrogen was selected as the lubricant for the sake of safety. Soon after, the authors will discuss the results and publish them in the new papers. Originality/value – An all liquid, liquid-vapor mixture, and all vapor, i.e. a continuous vaporization bulk flow model of density and viscosity for mixture fluid, is presented. The static and dynamic performance of hybrid bearings with two phase flow as lubricants are obtained.

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Numerical analysis of the electrospinning process for fabrication of composite fibers

Thermal Science ◽

10.2298/tsci2004377a ◽

2020 ◽

Vol 24 (4) ◽

pp. 2377-2383

Author(s):

Adnan Ahmed ◽

Lan Xu

Keyword(s):

Experimental Data ◽

Numerical Analysis ◽

Flow Velocity ◽

Composite Fiber ◽

Electrospinning Process ◽

Phase Flow ◽

Composite Fibers ◽

Two Phase ◽

Fiber Process ◽

Multi Phase

An electrospun composite fiber process is a multi-phase and multi-physics process. It was very difficult to study a charged jet in the electrospinning process for the fabrication of composite fibers by experiments. In this study, the liquid-solid two-phase flow in the electrospinning process for fabrication of composite fibers was researched numerically. The results showed the addition of conductive nanoparticles resulted in the increase of the jet flow velocity, and the decrease of the fiber?s diameter. The CFD results corresponded well with the experimental data.

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