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Rheological Properties of Cement-Based Grouts Determined by Different Techniques

Engineering（科研） 2014年第5期6卷 217-229页

作者： Mohammed Hatem Mohammed Roland Pusch Sven Knutsson gunnar hellstrom Department of Civil Environmental and Natural Resources EngineeringLulea University of TechnologyLulea Sweden Department of Civil Engineering University of MosulMosulIraq Department of Engineering Science and Mathematics Lulea University of TechnologyLuleaSweden

The rheological properties of cement-based grouts containing talc or palygorskite were investigated for optimizing fluidity and quick strengthening at injection. The fluidity controls the ability of grout to penetrate fractures and can be determined by pipe flow tests, Marsh funnel tests, mini-slump cone tests and rheometer tests. The grouts were 1) Talc for fluidity and strength by reacting with cement, 2) Palygorskite (attapulgite) for early gelation by being thixotropic, and 3) Powdered quartz for chemical integrity. The freshly prepared grouts behaved as Bingham fluids with viscosities from 0.151 to 0.464 Pas and yield stresses 5.2 Pa to 36.7 Pa. Statistical analysis of the flow test data converted Marsh flow time into viscosity. The pipe flow tests gave 26.5% higher values than the viscometer for grout with Portland cement and talc, and about 13.7% lower than the viscometer data for the grout with low-pH cement and talc. The big Marsh funnel gave values differing by 5.2% - 5.3% from those of the viscometer for grout with talc and Portland, and Merit 5000 cements. For grout with palygorskite the viscosity was at least twice that of the other grouts. Grout fluidity was positively affected by talc and negatively by palygorskite and early cement hydration.

关键词： Cement-Grout Marsh Funnel Quartz Powder Rheological Properties Thixotropic

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Turbulent Modulation in Particulate Flow: A Review of Critical Variables

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Engineering（科研） 2015年第10期7卷 597-609页

作者： Ammar Saber T.Staffan Lundstrom J.gunnar I.hellstrom Fluid and Experimental Mechanics Division Lulea University of TechnologyLuleaSweden Mechanical Engineering Department University of MosulMosulIraq

A review of the main mechanisms influencing turbulent modulation in the presence of spherical and non-spherical particles is presented. The review demonstrates the need for more numerical and experimental work with higher accuracy than obtained so far and the need to resolve the flow near the surface of particles with the aim to re-evaluate the quantitative effect of different parameters on turbulent modulation. The review reveals that non-spherical particles have more adverse effect on turbulence as compared to spherical ones, for the same ambient conditions.

关键词： Two Phase Flow Turbulent Modulation Non-Spherical Particle Stokes Number Particle Reynolds Number Length Scale Density Ratio

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Turbulence Modelling of a Single-Phase Flow Cyclone Gasifier

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Engineering（科研） 2017年第9期9卷 779-799页

作者： Pantea Hadi Jafari J.gunnar I.hellstrom B.Rikard Gebart Department of Engineering Sciences and Mathematics Division of Energy ScienceLulea University of TechnologyLuleaSweden Department of Engineering Sciences and Mathematics Division of Fluid and Experimental MechanicsLulea University of TechnologyLuleaSweden

The current work aims to make a foundation for an engineering design of a cyclone gasifier to be able not only to predict its flow field with a suitable accuracy but also to investigate a large number of design alternatives with limited computer resources. A good single-phase flow model that can form the basis in an Euler-Lagrange model for multi-phase flow is also necessary?for modelling the reacting flow inside a cyclone gasifier. The present paper provides an objective comparison between several popular turbulence modelling options including standard k-ε and SST with curvature corrections, SSG-RSM and LES Smagorinsky models, for the single-phase flow inside cyclone separators/gasifiers that can serve as a guide for further work on the reacting multi-phase flow inside cyclone gasifiers and similar devices. A detailed comparison between the models and experimental data for the mean velocity and fluctuating parts of the velocity profiles are presented. Furthermore, the capabilities of the turbulence models to capture the physical phenomena present in a cyclone gasifier that?affects the design process are investigated.

关键词： Cyclone Gasifier Turbulence Modelling Swirling Flow Pattern Secondary Flow

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Modelling Dam Break Evolution over a Wet Bed with Smoothed Particle Hydrodynamics: A Parameter Study

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Engineering（科研） 2015年第5期7卷 248-260页

作者： Patrick Jonsson Par Jonsen Patrik Andreasson T.Staffan Lundstrom J.gunnar I.hellstrom Department of Engineering Sciences and Mathematics LuleåUniversity of TechnologyLuleaSweden

When investigating water flow in spillways and energy dissipation, it is important to know the behavior of the free surfaces. To capture the real dynamic behavior of the free surfaces is therefore crucial when performing simulations. Today, there is a lack in the possibility to model such phenomenon with traditional methods. Hence, this work focuses on a parameter study for one alternative simulation tool available, namely the meshfree, Lagrangian particle method Smoothed Particle Hydrodynamics (SPH). The parameter study includes the choice of equation-of-state (EOS), the artificial viscosity constants, using a dynamic versus a static smoothing length, SPH particle spatial resolution and the finite element method (FEM) mesh scaling of the boundaries. The two dimensional SPHERIC Benchmark test case of dam break evolution over a wet bed was used for comparison and validation. The numerical results generally showed a tendency of the wave front to be ahead of the experimental results, i.e. to have a greater wave front velocity. The choice of EOS, FEM mesh scaling as well as using a dynamic or a static smoothing length showed little or no significant effect on the outcome, though the SPH particle resolution and the choice of artificial viscosity constants had a major impact. A high particle resolution increased the number of flow features resolved for both choices of artificial viscosity constants, but at the expense of increasing the mean error. Furthermore, setting the artificial viscosity constants equal to unity for the coarser cases resulted in a highly viscous and unphysical solution, and thus the relation between the artificial viscosity constants and the particle resolution and its impact on the behavior of the fluid needed to be further investigated.

关键词： SPH Dam Break Smoothed Particle Hydrodynamics

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