Zeitschriftenartikel: „Fluid-Grain“

1

KUROBE, Toshiji, Kazuhiro SHIMENO und Osamu IMANAKA. „Grain number controlled lapping with magnetic fluid.“ Journal of the Japan Society for Precision Engineering 54, Nr. 8 (1988): 1525–30. http://dx.doi.org/10.2493/jjspe.54.1525.

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2

Chareyre, Bruno, Chao Yuan, Eduard P. Montella und Simon Salager. „Toward multiscale modelings of grain-fluid systems“. EPJ Web of Conferences 140 (2017): 09027. http://dx.doi.org/10.1051/epjconf/201714009027.

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3

King, P. J., P. Lopez-Alcaraz, H. A. Pacheco-Martinez, C. P. Clement, A. J. Smith und M. R. Swift. „Instabilities in vertically vibrated fluid-grain systems“. European Physical Journal E 22, Nr. 3 (17.01.2007): 219–26. http://dx.doi.org/10.1140/epje/e2007-00001-6.

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4

Shi, Run, Huaiguang Xiao, Chengmeng Shao, Mingzheng Huang und Lei He. „Study on the Influence of Geometric Characteristics of Grain Membranes on Permeability Properties in Porous Sandstone“. Membranes 11, Nr. 8 (31.07.2021): 587. http://dx.doi.org/10.3390/membranes11080587.

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Studying the influence of grain characteristics on fluid flow in complex porous rock is one of the most important premises to reveal the permeability mechanism. Previous studies have mainly investigated the fluid flow laws in complex rock structures using an uncontrollable one single parameter of natural rock models or oversimplified control group models. In order to solve these problems, this paper proposes a novel method to reconstruct models that can independently control one single parameter of rock grain membranes based on mapping and reverse-mapping ideas. The lattice Boltzmann method is used to analyze the influence of grain parameters (grain radius, space, roundness, orientation, and model resolution) on the permeability characteristics (porosity, connectivity, permeability, flow path, and flow velocity). Results show that the grain radius and space have highly positive and negative correlations with permeability properties. The effect of grain roundness and resolution on permeability properties shows a strong regularity, while grain orientation on permeability properties shows strong randomness. This study is of great significance to reveal the fluid flow laws of natural rock structures.

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5

Selim, Mustafa I., Saleh H. El-Sharkawy und William J. Popendorf. „Supercritical Fluid Extraction of Fumonisin B1from Grain Dust“. Journal of Agricultural and Food Chemistry 44, Nr. 10 (Januar 1996): 3224–29. http://dx.doi.org/10.1021/jf940468j.

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6

Bottmann, Craig. „Thermal fluctuations in interfaces: From fluid-fluid interfaces to small-angle grain boundaries“. Materials Science and Engineering 81 (August 1986): 553–62. http://dx.doi.org/10.1016/0025-5416(86)90292-2.

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7

Enger, K., M. G. Mousavi und A. Safari. „Mathematical modelling of fluid flow in electromagnetically stirred weld pool“. IOP Conference Series: Materials Science and Engineering 1201, Nr. 1 (01.11.2021): 012025. http://dx.doi.org/10.1088/1757-899x/1201/1/012025.

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Abstract In this paper, a mathematical model has been proposed to study the relationship between electromagnetic stirring (EMS) weld parameters and the mode of fluid flow on grain refinement of AA 6060 weldments. For this purpose, fluid flow modelling using Navier-Stokes equation is described first, and then, the proposed mathematical approach has been discussed in detail. For demonstration, calculations to determine the fluid velocity in the weld pool of thin plate AA6060 were performed. The application of the model on the experimental results indicates that the best grain refinement is achieved at a transition mode from laminar to turbulent fluid flow.

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Wang, Honggui, und Hao Zhou. „Bulk Grain Cargo Hold Condensation Based on Computational Fluid Dynamics“. Applied Sciences 13, Nr. 23 (30.11.2023): 12878. http://dx.doi.org/10.3390/app132312878.

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In order to assess whether condensation will occur on the shipside of a bulk grain cargo hold during transportation at sea, this paper has established a ventilation model for the bulk cargo hold of the ship, and optimized the model according to the characteristics of the solid bulk grain stowed on a moving ship at sea. The temperature field, micro-airflow field and relative humidity field of the bulk grain in a cargo hold are simulated by using fluent software (v.2020). Incorporating the impact of grain moisture exchange, the Equilibrium Relative Humidity (ERH) method is introduced alongside the Dew Point (DP) method to determine the condensation on the shipside of the cargo hold. The results of simulation are in agreement with the practical observation results obtained from an actual ship with a heavy cargo damage claim. Conclusively, this paper finds that the risk of the condensation on the shipside of a bulk grain cargo hold always exists if the inner part of the shipside is directly in contact with the grain. Meanwhile, when the grain temperature near the shipside decreases, the moisture in the cargo hold will migrate to the shipside due to the temperature gradient. Furthermore, the longer the voyage, the more obvious the migration of moisture from the central part of the bulk grain to the shipside, and the greater the risk of condensation.

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Su, Chong, Li Da Zhu und Wan Shan Wang. „Simulation Research on Cutting Process of Single Abrasive Grain“. Advanced Materials Research 239-242 (Mai 2011): 3123–26. http://dx.doi.org/10.4028/www.scientific.net/amr.239-242.3123.

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Cutting processes of single abrasive grain were simulated respectively by fluid-solid interaction method and Smoothed Particle Hydrodynamics method. Advantages and disadvantages of the two methods were compared. Smoothed Particle Hydrodynamics method is superior to fluid-solid interaction method in simulating the deformation behavior of workpiece material for the motion of SPH particles. According to the simulation results, it is concluded that workpiece material occurs plastic deformation, flows to the side and front owing to the extrusion of abrasive grain, and finally forms chip in front of abrasive grain.

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Kruhl, Jörn H., Richard Wirth und Luiz F. G. Morales. „Quartz grain boundaries as fluid pathways in metamorphic rocks“. Journal of Geophysical Research: Solid Earth 118, Nr. 5 (Mai 2013): 1957–67. http://dx.doi.org/10.1002/jgrb.50099.

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11

Liu, Lele, Nengyou Wu, Changling Liu, Qingguo Meng, Haitao Tian, Yizhao Wan und Jianye Sun. „Maximum Sizes of Fluid-Occupied Pores within Hydrate-Bearing Porous Media Composed of Different Host Particles“. Geofluids 2020 (15.07.2020): 1–14. http://dx.doi.org/10.1155/2020/8880286.

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Hydraulic properties of hydrate-bearing sediments are largely affected by the maximum size of pores occupied by fluids. However, effects of host particle properties on the maximum size of fluid-occupied pores within hydrate-bearing sediments remain elusive, and differences in the maximum equivalent, incircle, and hydraulic diameters of fluid-occupied pores evolving with hydrate saturation have not been well understood. In this study, numerical simulations of grain-coating and pore-filling hydrate nucleation and growth within different artificial porous media are performed to quantify the maximum equivalent, incircle, and hydraulic diameters of fluid-occupied pores during hydrate formation, and how maximum diameters of fluid-occupied pores change with hydrate saturation is analyzed. Then, theoretical models of geometry factors for incircle and hydraulic diameters are proposed based on fractal theory, and variations of fluid-occupied pore shapes during hydrate formation are discussed. Results show that host particle properties have obvious effects on the intrinsic maximum diameters of fluid-occupied pores and introduce discrepancies in evolutions of the maximum pore diameters during hydrate formation. Pore-filling hydrates reduce the maximum incircle and hydraulic diameters of fluid-occupied pores much more significantly than grain-coating hydrates; however, hydrate pore habits have minor effects on the maximum equivalent diameter reduction. Shapes of fluid-occupied pores change little due to the presence of grain-coating hydrates, but pore-filling hydrates lead to much fibrous shapes of fluid-occupied pores.

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Li, Xiang Mei, Jie Yu Zhang, Chun Tao Liu, Ji Fang Xu und Zhong Ming Ren. „Effect of Pulling Velocity on the Unidirectional Solidification Phenomenon of DZ417G Superalloy“. Advanced Materials Research 148-149 (Oktober 2010): 539–43. http://dx.doi.org/10.4028/www.scientific.net/amr.148-149.539.

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In this study, the influence of pulling velocity on temperature field, fluid field and grain structure of a unidirectionally solidified superalloy DZ417G cylindrical casting was investigated by using a 3D cellular automaton finite element (CAFE) model within commercial software CALCOSOFT. The predictions show that temperature distribution in the casting is well in accordance with the experiment result. The solidification front and fluid field are sensitive to changes in pulling velocity. And the pulling velocity should be controlled less than 0.5 mm/s in our experiment so as to effectively decrease the grain number and mean grain deviation.

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Morgan, Miles, und Bjørnar Sandnes. „From Darcy to Gaussian to fully mobilised grain flow in a confined channel“. EPJ Web of Conferences 249 (2021): 03041. http://dx.doi.org/10.1051/epjconf/202124903041.

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Fluid-driven grain flow through a confined channel filled with non-buoyant grains is herein observed to exist in three regimes according to total imposed flow rate. (1) At low imposed flow rates, no grain flow occurs as the fluid stress is insufficient to mobilise the grains and Darcy flow is observed. (2) At a sufficient imposed flow rate, grains begin to flow at the top of the channel with self-similar Gaussian velocity profiles that become faster and encroach deeper into the channel with increased flow rate. (3) At high flow rates, significant grain flow occurs at the base of the channel, distorting the Gaussian profile, resulting in a gradual transition towards a more symmetric, full-channel flow. Each regime, and the transitions between them, is discussed in relation to experimental grain velocity measurements.

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Sakai, Yuichi, und Norifumi Hotta. „Laboratory investigation of the effects of grain size on the dynamics of debris flows: Measurement of pore fluid pressure in an open channel“. E3S Web of Conferences 415 (2023): 01022. http://dx.doi.org/10.1051/e3sconf/202341501022.

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The dynamics of debris flow depend on internal stress components, such as particle–particle stress, the stress exerted by pore water, and interactions between particles and pore water. Although dominant internal stress components depend on the grain size composition, the effects of grain size on the dynamics of debris flow are not fully understood. To investigate the effects of grain size on the dynamics of debris flows, pore fluid pressures were measured in an open channel experiment. In the experiment, monodisperse debris flows were triggered for five different grain sizes: 0.2, 0.8, 1.3, 2.2, and 2.9 mm. The pore fluid pressures in debris flows of 0.2 mm grains had larger excess pressures over the hydrostatic pressure, and were close to the total normal stress, while those of other grain sizes had smaller excess pressures and were relatively close to the hydrostatic pressure. Comparing the measured friction factors and theoretical ones for stony debris flows, particle–particle stress dominated in debris flows, except for 0.2 mm grains, and the measured excess pore pressures could be explained by the Reynolds stress of pore fluid due to shear by particles in laminar motion. By contrast, particle–particle stress did not dominate in debris flows of grain size 0.2 mm, and a large portion of the particles was in suspension affected by turbulence. These differences in flow dynamics may correspond to the flow transition from laminar to turbulent flow described by the threshold of relative flow depth, which is the ratio of the flow depth to grain size.

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Lagoeiro, Leonardo, und Cristiane C. Gonçalves. „SEM observation of grain boundary structures in quartz-iron oxide rocks deformed at intermediate metamorphic conditions“. Anais da Academia Brasileira de Ciências 83, Nr. 3 (15.07.2011): 875–90. http://dx.doi.org/10.1590/s0001-37652011005000015.

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Several studies have demonstrated the effect of a second phase on the distribution of fluid phase and dissolution of quartz grains. However, as most observations came from aggregates deformed under hydrostatic stress conditions and mica-bearing quartz rocks, 3-D distribution of pores on quartz-quartz (QQB) and quartz-hematite boundaries (QHB) has been studied. Several fracture surfaces oriented according to finite strain ellipsoid were analyzed. The pore distribution characterizes the porosity and grain shape as highly anisotropic, which results from the nature and orientation of boundaries. QHB have physical/chemical properties very different from QQB, once the hematite plates have strong effect on wetting behavior of fluid, likewise micas in quartzites. They are pore-free flat surfaces, normal to compression direction, suggesting that they were once wetted with a continuous fluid film acting as faster diffusion pathway. At QQB, the pores are faceted, isolated, close to its edges reflecting the crystallographic control and an interconnected network of fluid along grain junctions. The QQB facing the extension direction are sites of fluid concentration. As consequence, the anisotropic dissolution and grain growth were responsible for the formation of hematite plates and tabular quartz grains significantly contributing for the generation of the foliation observed in the studied rocks.

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Agersborg, Remy, Tor Arne Johansen, Morten Jakobsen, Jeremy Sothcott und Angus Best. „Effects of fluids and dual-pore systems on pressure-dependent velocities and attenuations in carbonates“. GEOPHYSICS 73, Nr. 5 (September 2008): N35—N47. http://dx.doi.org/10.1190/1.2969774.

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The effects of fluid substitution on P- and S-wave velocities in carbonates of complex texture are still not understood fully. The often-used Gassmann equation gives ambiguous results when compared with ultrasonic velocity data. We present theoretical modeling of velocity and attenuation measurements obtained at a frequency of [Formula: see text] for six carbonate samples composed of calcite and saturated with air, brine, and kerosene. Although porosities (2%–14%) and permeabilities [Formula: see text] are relatively low, velocity variations are large. Differences between the highest and lowest P- and S-wave velocities are about 18% and 27% for brine-saturated samples at 60 and [Formula: see text] effective pressure, respectively. S-wave velocities are measured for two orthogonal polarizations; for four of six samples, anisotropy is revealed. TheGassmann model underpredicts fluid-substitution effects by [Formula: see text] for three samples and by as much as 5% for the rest of the six samples. Moreover, when dried, they also show decreasing attenuation with increasing confining pressure. To model this behavior, we examine a pore model made of two pore systems: one constitutes the main and drainable porosity, and the other is made of undrained cracklike pores that can be associated with grain-to-grain contacts. In addition, these dried rock samples are modeled to contain a fluid-filled-pore system of grain-to-grain contacts, potentially causing local fluid flow and attenuation. For the theoretical model, we use an inclusion model based on the [Formula: see text]-matrix approach, which also considers effects of pore texture and geometry, and pore fluid, global- and local-fluid flow. By using a dual-pore system, we establish a realistic physical model consistently describing the measured data.

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Williams, Y. J., W. J. Wales, P. T. Doyle, A. R. Egan und C. R. Stockdale. „Effects of grain or hay supplementation on the chewing behaviour and stability of rumen fermentation of dairy cows grazing perennial ryegrass-based pasture in spring“. Australian Journal of Experimental Agriculture 45, Nr. 12 (2005): 1519. http://dx.doi.org/10.1071/ea04084.

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Cows grazing highly digestible pasture in early spring can have very low rumen fluid pH that can negatively impact on the efficiency of microbial digestion. In this experiment, cows in early lactation grazed perennial ryegrass (Lolium perenne L.)-based pasture alone at low or high allowances, or at a low allowance supplemented with either a cereal grain pellet, a chopped hay cube or a cube containing cereal grain and chopped hay to determine the effects of the addition of neutral detergent fibre as hay on chewing behaviour and stability of rumen fermentation. The hypotheses tested were that: (i) supplementing high digestibility ryegrass pasture with pelleted cereal grain would increase the proportion of the day that the pH of rumen fluid was below 6.0 and would decrease the rate of degradation of neutral detergent fibre in pasture and hay; and (ii) the inclusion of chopped hay with the cereal grain supplement in cubes would reduce the proportion of the day that the rumen fluid pH was below 6.0 and restore the rate of degradation of neutral detergent fibre in pasture and hay to that in unsupplemented cows. Rumen fluid pH was highest (P<0.05) in cows fed a chopped hay cube and lowest (P<0.05) in cows fed a cube containing cereal grain and chopped hay, with no significant (P>0.05) difference between those fed pasture only or cereal grain pellets. The introduction of grain, with or without hay, did not substantially alter the pattern or magnitude of changes in rumen fluid pH, but did reduce (P<0.05) the rate of degradation of neutral detergent fibre in pasture (5.3 v. 7.6%/h) and hay (2.7 v. 5.0%/h) in the rumen. Rumen degradation rates of pasture dry matter and neutral detergent fibre were not improved by adding chopped hay. Total volatile fatty acid concentrations in rumen fluid were highest (P<0.05) on the high pasture allowance treatment and lowest (P<0.05) on the low pasture allowance and the chopped hay cube treatments. Supplementation with grain reduced (P<0.05) the proportion of acetate and increased (P<0.05) the proportion of propionate in total volatile fatty acids. There were no significant (P>0.05) effects of dietary treatment on time spent grazing or on rate of biting while grazing. Cows in treatments receiving grain supplements (532 min) and those in the high pasture allowance treatment (566 min) spent more (P<0.05) time ruminating than those in the low pasture allowance (415 min) and chopped hay cube (465 min) treatments. The relative contributions of low pH and of starch to the reduction in rates of dry matter and neutral detergent fibre degradation in the rumen cannot be determined from this experiment, however, it is likely that both factors contribute to a relative increase in the metabolic activity of non-cellulolytic microorganisms.

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Ellis, Michelle H., Martin C. Sinha, Tim A. Minshull, Jeremy Sothcott und Angus I. Best. „An anisotropic model for the electrical resistivity of two-phase geologic materials“. GEOPHYSICS 75, Nr. 6 (November 2010): E161—E170. http://dx.doi.org/10.1190/1.3483875.

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Electrical and electromagnetic surveys of the seafloor provide valuable information about the macro and microscopic properties of subseafloor sediments. Sediment resistivity is highly variable and governed by a wide range of properties including pore-fluid salinity, pore-fluid saturation, porosity, pore geometry, and temperature. A new anisotropic, two-phase, effective medium model describes the electrical resistivity of porous rocks and sediments. The only input parameters required are the resistivities of the solid and fluid components, their volume fractions and grain shape. The approach makes use of the increase in path length taken by an electrical current through an idealized granular medium comprising of aligned ellipsoidal grains. The model permits both solid and fluid phases to have a finite conductivity (useful for dealing with surface charge conduction effects associated with clay minerals) and gives results independent of grain size (hence, valid for a wide range of sediment types). Furthermore, the model can be used to investigate the effects of grain aspect ratio and alignment on electrical resistivity anisotropy. Good agreement was found between the model predictions and laboratory measurements of resistivity and porosity on artificial sediments with known physical properties.

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19

Jara, Andrea, und Miguel Cabrera. „Planar column collapse of elongated grains“. EPJ Web of Conferences 249 (2021): 06006. http://dx.doi.org/10.1051/epjconf/202124906006.

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The granular column collapse is a benchmark configuration for the study of granular flows in dry, saturated, and submerged conditions. The collapse sequence and resultant mobility is acknowledged to be controlled by the column aspect ratio, while grain properties define the relative transition of each stage. Grain shape effects are found to modify the global shear resistance of granular media, with a strong and coupled interaction when interacting with a fluid. In this work, we present the first steps towards the study of grain shape effects in a column collapse when interacting with an ambient fluid. For this purpose, we use a planar configuration and explore the collapse of a column consisting of rod-like grains and study the initial and after collapse grain orientations. On it, the mobilized grains deposit in a preferential horizontal orientation, but further experiments are required to confirm if a nematic configuration can be achieved.

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Zhang, Huan, Jun Chen und Feng Feng. „Numerical Simulation of Fluid-Structure Interaction in SRM under Cold-Flow Impact“. Applied Mechanics and Materials 281 (Januar 2013): 245–49. http://dx.doi.org/10.4028/www.scientific.net/amm.281.245.

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The process of impacting adherent casting solid rocket motor under cool-flow impact was simulated using two-way fluid-solid coupling method by ANSYS workbench14.0. In order to truly reflect the interaction between the establishment of the flow field in the cool air impact process and the SRM grain, the impact pressure to the SRM grain was provided with reference to the structure of the shock tube. The process of the establishment and spread of the flow field pressure was simulated, according to the grain deformation under the cool air impact, the maximum deformation position of the grain was determined. The relationship between the amount of grain deformation and flow field pressure gradient was summed up by observing the law of flow field pressure distribution along the axial coupling surface.

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Durán, O., B. Andreotti und P. Claudin. „Turbulent and viscous sediment transport – a numerical study“. Advances in Geosciences 37 (06.05.2014): 73–80. http://dx.doi.org/10.5194/adgeo-37-73-2014.

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Abstract. Sediment transport is studied as a function of the grain to fluid density ratio using two phase numerical simulations based on a discrete element method (DEM) for particles coupled to a continuum Reynolds averaged description of hydrodynamics. At a density ratio close to unity (typically under water), sediment transport occurs in a thin layer at the surface of the static bed, and is called bed load. Steady, or "saturated" transport is reached when the fluid borne shear stress at the interface between the mobile grains and the static grains is reduced to its threshold value. The number of grains transported per unit surface therefore scales as the excess shear stress. However, the fluid velocity in the transport layer remains almost undisturbed so that the mean grain velocity scales with the shear velocity u*. At large density ratio (typically in air), the vertical velocities are large enough to make the transport layer wide and dilute. Sediment transport is then called saltation. In this case, particles are able to eject others when they collide with the granular bed. The number of grains transported per unit surface is selected by the balance between erosion and deposition and saturation is reached when one grain is statistically replaced by exactly one grain after a collision, which has the consequence that the mean grain velocity remains independent of u*. The influence of the density ratio is systematically studied to reveal the transition between these two transport regimes. Finally, for the subaqueous case, the grain Reynolds number is lowered to investigate the change from turbulent and viscous transport.

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Geng, Ling Xin, Li Jian Zhang und Qing Xiang Shi. „Fluid Field Analysis for Cyclone Separator Used on Grain Cleaning“. Advanced Materials Research 605-607 (Dezember 2012): 1369–71. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1369.

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Gas velocity in cyclone separator is measured by testing with laser Doppler velocimeter in this paper. The measuring results indicates that tangential velocity, axial velocity, radial velocity of air distribute following some certain rules, reasonable selected structure parameters can improve separating efficiency

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ZHANG, Chi, Hiroyuki YOSHIMATSU, Yasunori IWAHORI und Shinro ABE. „Numerical simulation of grain-fluid flow due to slope collapse“. Journal of the Japan Landslide Society 41, Nr. 1 (2004): 9–17. http://dx.doi.org/10.3313/jls.41.9.

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Fernández, M. P., J. F. Rodriguez, M. T. García, A. de Lucas und I. Gracia. „Application of Supercritical Fluid Extraction to Brewer's Spent Grain Management“. Industrial & Engineering Chemistry Research 47, Nr. 5 (März 2008): 1614–19. http://dx.doi.org/10.1021/ie0708529.

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Huang, Yongsheng, Takayuki Nakatani, Michihiko Nakamura und Catherine McCammon. „Experimental constraint on grain-scale fluid connectivity in subduction zones“. Earth and Planetary Science Letters 552 (Dezember 2020): 116610. http://dx.doi.org/10.1016/j.epsl.2020.116610.

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Marzougui, Donia, Bruno Chareyre und Julien Chauchat. „Microscopic origins of shear stress in dense fluid–grain mixtures“. Granular Matter 17, Nr. 3 (21.04.2015): 297–309. http://dx.doi.org/10.1007/s10035-015-0560-6.

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27

Mavko, Gary, und Diane Jizba. „Estimating grain‐scale fluid effects on velocity dispersion in rocks“. GEOPHYSICS 56, Nr. 12 (Dezember 1991): 1940–49. http://dx.doi.org/10.1190/1.1443005.

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The magnitude of the grain‐scale local flow effect on velocity dispersion in saturated rocks is quantified, by estimating the high‐frequency unrelaxed shear and bulk frame moduli, which are then combined with the Biot formulation to predict total dispersion. The method is relatively independent of assumptions about idealized pore geometries and unknown parameters such as pore aspect ratios. The local flow effect depends on the heterogeneity of pore stiffness, in particular the presence of compliant cracks and grain contacts; the pressure dependence of the dry rock properties is shown to contain the essential information about the distribution of pore stiffnesses needed to estimate the high‐frequency saturated behavior. To first order, the unrelaxed wet frame compressibility at any given pressure is shown to be approximately the dry frame compressibility at very high pressure; second order corrections add the additional compressibility gained by replacing an amount of mineral equal to the compliant pore volume with fluid. The method predicts that the difference between relaxed and unrelaxed shear compliance is simply proportional to that in bulk. The results for total dispersion (local flow plus Biot) explain quite well the measured P- and S-wave dispersion for a variety of saturated rocks.

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Ma, Rui, Zhibo Dong, Yanhong Wei, Xiaohong Zhan und Yong Wang. „Columnar grain growth pattern with fluid flowing in molten pool“. Crystal Research and Technology 44, Nr. 11 (November 2009): 1197–204. http://dx.doi.org/10.1002/crat.200900398.

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RAMESH, T., S. MADHUSREE, S. RATHIKA, S. MEENA und K. RAJA. „Drone based herbicide application in greengram (Vigna radiata)“. Indian Journal of Agricultural Sciences 94, Nr. 3 (12.03.2024): 329–32. http://dx.doi.org/10.56093/ijas.v94i3.144541.

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An experiment was conducted during winter (rabi) season of 2023 at Anbil Dharmalingam Agricultural College and Research Institute, (Tamil Nadu Agricultural University), Tiruchirappalli, Tamil Nadu to assess the effect of drone based herbicide application in greengram. Results showed that drones could be effectively used for spraying of pre-emergence herbicide to control weeds and increase the yield of greengram. Further, application of pendimethalin 0.75 kg/ha with spray fluid of 60 litre/ha precisely through drones controlled the weeds effectively (WCE of 81.8%), increased grain yield, saved herbicide dose and spray fluid to the tune of 6.9%, 25% and 88% respectively than manual spray of pendimethalin 1.0 kg/ha with spray fluid of 500 litre/ ha. Thus, application of pendimethalin 0.75 kg/ha with spray fluid of 60 litre/ha was considered as the optimum dosage and spray fluid for drone spray to control weeds, increase grain yield and profit in greengram, considering the reduced dose of herbicide as well as the labour scarce situation.

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Wei, Yan Hong, Yan Li Xu, Zhi Bo Dong und Ji Lin Xiao. „Three Dimensional Monte Carlo Simulation of Grain Growth in HAZ of Stainless Steel SUS316“. Key Engineering Materials 353-358 (September 2007): 1923–26. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1923.

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The stainless steel SUS316 grain growth process in heat affected zone (HAZ) of gas tungsten arc welding (GTAW) process is studied with Monte Carlo (MC) simulation. The heat transfer and fluid flow model provides the thermal history and thermal distribution of the weldments for MC grain growth simulation. The grain growth evolution is simulated both in isothermal and in HAZ environment. The simulating results show clearly the “thermal pinning” effect on the grain growth evolution in HAZ compared with the isothermal results.

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Tai, Yih-Chin, Hock-Kiet Wong und Ching-Yuan Ma. „A Simplex Multi-Phase Approach for Modelling Debris Flows in Smoothed-Terrain-Following Coordinate System“. E3S Web of Conferences 415 (2023): 02022. http://dx.doi.org/10.1051/e3sconf/202341502022.

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Herewith we present a multi-phase model for debris flows, of which the flow body is supposed to be composed of water, fine sediment (clay/silt) and grains. The rheology of debris flows varies due to the dynamical variation of the composition concentrations. In the present study the component of silt/clay is an individual phase, and its concentration plays a key role in determining the rheology of the interstitial fluid. Hence, there are three phases in the mixture, the grain phase, the clay phase and the water phase from the viewpoint of mass conservation. Only the grain phase and fluid phase are considered in the momentum conservation, since the clay is suspended in the fluid and the relative motion is negligible within the interstitial fluid. The grain constituent is treated as a frictional Coulomb-like continuum, and the viscosity of the interstitial depends on the clay concentration. The resultant models are given in a smoothed-terrain-following coordinate system, a compromise between the constraint of shallow curvature for the terrain-fitting coordinate system and retaining the high resolution of the topography. The numerical implementation is developed with the CUDA-library for GPU-high-performance computations. The feasibility and applicability will be presented by back calculation of a historical event.

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Frank-Gilchrist, Donya P., Allison Penko und Joseph Calantoni. „Investigation of Sand Ripple Dynamics with Combined Particle Image and Tracking Velocimetry“. Journal of Atmospheric and Oceanic Technology 35, Nr. 10 (Oktober 2018): 2019–36. http://dx.doi.org/10.1175/jtech-d-18-0054.1.

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AbstractAccurately assessing the response of sediments to oscillatory flows requires high-resolution fluid velocity and sediment transport measurements at the fluid–sediment interface. Fluid and sediment grain velocities were measured simultaneously with combined particle image and tracking velocimetry under oscillatory flows over movable sand ripples. Three high-speed cameras equipped with varying optical filters were used to distinguish between fluorescent fluid tracers and the grains, from which the fluid and grain velocities were determined, respectively. Individual grains were tracked during transport to determine velocities and trajectories. Sediment grains were first mobilized by a vortex impacting the bed during flow reversal and suspended into the water column just prior to vortex ejection from the ripple crest, similar to previous observations. During phases of maximum flow velocity, additional grains were mobilized by the shear stress and were subsequently suspended. The flow reversed and similar observations were made in the opposite direction. Consequently, four peaks in suspended sediment concentration were observed throughout the flow cycle, consistent with previous observations. However, some previous researchers attributed peaks in suspended sediment concentration occurring during phases of maximum flow velocity to sediment-laden vortices that were shed from adjacent ripples. The measured sediment grain velocities were of similar magnitude and phase to the near-bed fluid velocities when the grains were being advected with the flow. Measurements of suspended sediment concentration agreed well with semiempirical formulations having an average root-mean-square deviation of approximately 4 × 10−5 m3 m−3. Predictions of settling velocity also compared well with the laboratory estimates, agreeing to within 90%.

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Lima, Nicolao C., Willian R. Assis, Carlos A. Alvarez und Erick M. Franklin. „Grain-scale computations of barchan dunes“. Physics of Fluids 34, Nr. 12 (Dezember 2022): 123320. http://dx.doi.org/10.1063/5.0121810.

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Barchans are crescent-shaped dunes commonly found in diverse environments and scales: from the 10-cm-long barchans found under water to the 1-km-long barchans on Mars, passing by the 100-m-long dunes on Earth's deserts. Although ubiquitous in nature, there is a lack of grain-scale computations of the growth and evolution of those bedforms. In this paper, we investigate the values of grain properties (coefficients of sliding friction, rolling friction, and restitution) necessary to carry out numerical simulations of subaqueous barchans with CFD–DEM (computational fluid dynamics–discrete element method), and how the values of those coefficients change the barchan dynamics. We made use of LES (large eddy simulation) for the fluid, varied the coefficients of sliding friction, rolling friction, and restitution in the DEM, and compared the outputs with experiments. We show (i) for the case of glass spheres, the values of coefficients for correctly obtaining the dune morphology, timescales, trajectories of individual grains, and forces experienced by grains; (ii) the LES meshes allowing computations of bedload while capturing the main disturbances of the fluid flow; (iii) how different values of coefficients affect the morphology of barchans; and (iv) that spheres with higher coefficients of rolling friction can be used for simulating barchans consisting of angular grains. Our results represent a significant step for performing simulations that capture, at the same time, details of the fluid flow (large eddies) and grains' motion (individual particles).

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Damsgaard, A., D. L. Egholm, J. A. Piotrowski, S. Tulaczyk, N. K. Larsen und C. F. Brædstrup. „A new methodology to simulate subglacial deformation of water saturated granular material“. Cryosphere Discussions 9, Nr. 4 (13.07.2015): 3617–60. http://dx.doi.org/10.5194/tcd-9-3617-2015.

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Abstract. The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions. The rheology of a water-saturated granular bed may include both plastic and rate-dependent dilatant hardening or weakening components, depending on the rate of deformation, the material state, clay mineral content, and the hydrological properties of the material. The influence of the fluid phase is negligible when relatively permeable sediment is deformed. However, by reducing the local permeability, fast deformation can cause variations in the pore-fluid pressure. The pressure variations weaken or strengthen the granular phase, and in turn influence the distribution of shear strain with depth. In permeable sediments the strain distribution is governed by the grain-size distribution and effective normal stress and is typically on the order of tens of centimeters. Significant dilatant strengthening in impermeable sediments causes deformation to focus at the hydrologically more stable ice–bed interface, and results in a very shallow cm-to-mm deformational depth. The amount of strengthening felt by the glacier depends on the hydraulic conductivity at the ice–bed interface. Grain-fluid feedbacks can cause complex material properties that vary over time, and which may be of importance for glacier stick-slip behavior.

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Murphy, William F., Kenneth W. Winkler und Robert L. Kleinberg. „Acoustic relaxation in sedimentary rocks: Dependence on grain contacts and fluid saturation“. GEOPHYSICS 51, Nr. 3 (März 1986): 757–66. http://dx.doi.org/10.1190/1.1442128.

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Partial fluid saturation affects absorption and dispersion in sandstones. The proposed theoretical model describes acoustic relaxation due to local fluid flow. Previously proposed models of local flow were based on microgeometries not representative of sedimentary rocks; they were unable to describe the behavior of partially saturated sandstones. The new model is based upon observed microstructures in sandstones. A fraction of the grain contacts in sandstones are permeated by sheet‐like gaps. The incomplete solid‐solid contact allows an interconnected fluid film to exist between the grain surfaces. The model consists of a narrow gap connected to a finite annular pore. An acoustic stress wave drives the film out of the narrow contact region and into the adjacent pore. The viscous flow results in a dissipation of energy. The model predicts the real and imaginary parts of the complex frame moduli as a function of frequency and fluid saturation. The predictions agree well with experimental results.

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Xu, Feng, Feiyu Xiong, Ming-Jian Li und Yanping Lian. „Three-Dimensional Numerical Simulation of Grain Growth during Selective Laser Melting of 316L Stainless Steel“. Materials 15, Nr. 19 (30.09.2022): 6800. http://dx.doi.org/10.3390/ma15196800.

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The grain structure of the selective laser melting additive manufactured parts has been shown to be heterogeneous and spatially non-uniform compared to the traditional manufacturing process. However, the complex formation mechanism of these unique grain structures is hard to reveal using the experimental method alone. In this study, we presented a high-fidelity 3D numerical model to address the grain growth mechanisms during the selective laser melting of 316 stainless steel, including two heating modes, i.e., conduction mode and keyhole mode melting. In the numerical model, the powder-scale thermo-fluid dynamics are simulated using the finite volume method with the volume of fluid method. At the same time, the grain structure evolution is sequentially predicted by the cellular automaton method with the predicted temperature field and the as-melted powder bed configuration as input. The simulation results agree well with the experimental data available in the literature. The influence of the process parameters and the keyhole and keyhole-induced void on grain structure formation are addressed in detail. The findings of this study are helpful to the optimization of process parameters for tailoring the microstructure of fabricated parts with expected mechanical properties.

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Zhou, Mengmeng, Fengshuai Fan, Zhuo Zheng und Chenyang Ma. „Modeling of Grouting Penetration in Porous Medium with Influence of Grain Distribution and Grout–Water Interaction“. Processes 10, Nr. 1 (30.12.2021): 77. http://dx.doi.org/10.3390/pr10010077.

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In this study, a numerical model of grouting penetration in a porous medium is established. The fluid flow in the interstices of the porous medium is directly modeled by Navier–Stokes equations. The grouting process is considered as a two-phase flow problem, and the level set method is used to characterize the interaction between grout and groundwater. The proposed model has considered the nuances for each grain during grouting penetration, instead of representing the fluid flow as a continuum process. In the simulation, three kinds of porosity (0.3; 0.4; 0.5) and two kinds of grain size distribution (0.5~1 mm; 1~2 mm) are used. Results show that: the pressure drop along penetration distance is approximately in a linear trend. The variation of filling degree along grouting distance approximately obeys a quadratic polynomial function. The injection pressure is influenced by the porosity and grain size of the porous medium, especially by the former. A theoretical analysis is carried out to propose an analytical solution of the grouting penetration. The analytical solution gives a good estimation when the grain amounts in the porous medium are small, and the difference becomes larger as the grain amounts increase.

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Leary, Kate C. P., Leah Tevis und Mark Schmeeckle. „Spatiotemporal bedload transport patterns over two-dimensional bedforms“. Earth Surface Dynamics 11, Nr. 5 (05.09.2023): 835–47. http://dx.doi.org/10.5194/esurf-11-835-2023.

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Abstract. Despite a rich history of studies investigating fluid dynamics over bedforms and dunes in rivers, the spatiotemporal patterns of sub-bedform bedload transport remain poorly understood. Previous experiments assessing the effects of flow separation on downstream fluid turbulent structures and bedload transport suggest that localized, intermittent, high-magnitude transport events (i.e., permeable splat events) play an important role in both downstream and cross-stream bedload transport near flow reattachment. Here, we report results from flume experiments that assess the combined effects of flow separation–reattachment and flow re-acceleration over fixed two-dimensional bedforms (1.7 cm high; 30 cm long). A high-speed camera observed bedload transport along the entirety of the bedform at 250 frames per second. Grain trajectories, grain velocities, and grain transport directions were acquired from bedload images using semiautomated particle-tracking techniques. Downstream and vertical fluid velocities were measured 3 mm above the bed using laser Doppler velocimetry (LDV) at 15 distances along the bedform profile. Mean downstream fluid velocity increases nonlinearly with increasing distance along the bedform. However, observed bedload transport increases linearly with increasing distance along the bedform, except at the crest of the bedform, where both mean downstream fluid velocity and bedload transport decrease substantially. Bedload transport time series and manual particle-tracking data show a zone of high-magnitude, cross-stream transport near flow reattachment, suggesting that permeable splat events play an essential role in the region downstream of flow reattachment.

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Xing, Bo. „Investigation on Grain Refinement of AZ31 Alloy by Self-Inoculation Method“. Advanced Materials Research 1030-1032 (September 2014): 108–11. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.108.

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The grain refining technology of AZ31 alloy by using self-inoculation method (SIM) has been developed. Results indicated that SIM significantly decreased the grain size of as-cast AZ31 billet from 287 to 58 μm, changed the morphologies and size of the β-Mg17Al12 phase and decreased the solute elements segregation along grain boundaries. The average grain size is sensitive to the diameter of a cast rod; the microstructures of the large diameter rod are relatively inhomogeneous. The grain refinement was mainly attributed to the grain multiplication which derives from heterogeneous nucleation induced by self-inoculants and free crystals and dendrite fragments enhanced by fluid director, combined with a high solidification rate of alloy melt in the metal mold.

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Stenvall, C. A., A. Fagereng, J. F. A. Diener, C. Harris und P. E. Janney. „Sources and Effects of Fluids in Continental Retrograde Shear Zones: Insights from the Kuckaus Mylonite Zone, Namibia“. Geofluids 2020 (01.08.2020): 1–21. http://dx.doi.org/10.1155/2020/3023268.

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Midcrustal rocks in retrograde metamorphic settings are typically H2O-undersaturated and fluid-absent and have low permeability. Exhumed continental retrograde faults, nonetheless, show evidence for the operation of fluid-mediated weakening mechanisms during deformation at midcrustal conditions. To explore the origin and effects of fluids in retrograde faults, we study the Kuckaus Mylonite Zone (KMZ), an exhumed crustal-scale, strike-slip shear zone in the southern Namibian Namaqua Metamorphic Complex. The KMZ deformed quartzofeldspathic migmatised gneisses at midcrustal retrograde conditions (450-480°C, 270-420 MPa) in the Mesoproterozoic, 40 Ma after granulite facies peak metamorphism at 825°C and 550 MPa. The mylonites contain fully hydrated retrograde mineral assemblages, predominantly adjacent to anastomosing high-strain zones, providing evidence of local H2O saturation and fluid presence during deformation. Whole rock and quartz vein δ18O values suggest that at least some of the fluids were meteoric in origin. The rocks across the shear zone retain the effect of different protoliths, implying little effect of fluid-rock interaction on whole rock major element chemistry. Together with a general scarcity of quartz veins, this suggests that fluid/rock ratios remained low in the KMZ. However, even small amounts of H2O allowed reaction weakening and diffusion-precipitation, followed by growth and alignment of phyllosilicates. In the ultramylonites, a fine grain size in the presence of fluids allowed for grain size sensitive creep. We conclude that the influx of even small volumes of fluids into retrograde shear zones can induce drastic weakening by facilitating grain size sensitive creep and retrograde reactions. In retrograde settings, these reactions consume fluids, and therefore elevated fluid pressures will only be possible after considerable weakening has already occurred. Our findings imply that the range of seismic styles recently documented at active retrograde transform faults may not require high fluid pressures but could also arise from other local weakening mechanisms.

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Lu, Jia Bin, Qiu Sheng Yan, Hong Tian und Wei Qiang Gao. „Effect of Abrasive on the Machining Performance the EMR-Effect-Based Tiny-Grinding Wheel“. Advanced Materials Research 135 (Oktober 2010): 24–29. http://dx.doi.org/10.4028/www.scientific.net/amr.135.24.

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Based on the electro-magneto-rheological (EMR) effect, the Fe3O4-based EMR fluid dispersed with micron-sized finishing abrasives is used as a polishing fluid to form a dynamical tiny-grinding wheel under an electro-magnetically coupled field. Using this EMR-effect-based tiny-grinding wheel, experiments were conducted to investigate the effect of the grain size, content and material of abrasive on material removal effect of normal glass. Results indicate that the abrasive can change the chain-like structure of the EMR-effect-based tiny-grinding wheel and influence the material removal ability of the tiny-grinding wheel remarkably. The material removal amount increases with the increase of the content of diamond abrasive in the EMR fluid, and grows slowly when the proportion of diamond abrasive exceeds to 6%. While the grain size of abrasive increases, the material removal amount increases at the beginning and decreases afterwards. The effect of abrasive on material removal depends on the hardness of abrasive, the greater the abrasive hardness, the higher the material removal efficiency. The machined area has a close relationship with both the density and grain size of abrasive.

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Zhao, Jin Sheng, Ying Jun Ju, Mei Rong Tang und Rong Huan Chen. „Experimental Study on the Corrosion Behavior of Produced Fluid on J55 Steel during CO₂ Flooding“. Key Engineering Materials 773 (Juli 2018): 179–83. http://dx.doi.org/10.4028/www.scientific.net/kem.773.179.

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CO2 flooding has been widely used in oil field development, but the produced fluid is easy to cause corrosion of tubing and casing. In order to determine the corrosion behavior of produced fluid on J55 steel during CO2 flooding, we use the simulated oil well produced fluid as corrosive medium and conduct the corrosion simulation experiment at high temperature and high pressure. The experimental results showed that the crystalline grain size of corrosion film surface is different for the different CO2 partial pressure. When CO2 partial pressure is greater than the critical pressure, the crystalline grain is not oblique six-party crystal structure, and the grains become small and compact, so the corrosion product film should have a good corrosion inhibition. Both static and dynamic corrosion of samples are serious. The research has a theoretical guiding significance on corrosion protection during CO2 flooding.

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Chen, Qipeng, und Houfa Shen. „Direct Macroscopic Modeling of Grain Structure and Macrosegregation with a Cellular Automaton–Finite Element Model“. Metals 9, Nr. 2 (02.02.2019): 177. http://dx.doi.org/10.3390/met9020177.

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Grain structure and macrosegregation are two main factors determining mechanical properties of components and are strongly coupled during alloy solidification. A two-dimensional (2D) cellular automaton (CA)–finite element (FE) model is developed to achieve a direct macroscopic modeling of grain structure and macrosegregation during the solidification of binary alloys. With the conservation equations of mass, momentum, energy, and solute solved by a macroscopic FE model and the grain structure described by a microscopic CA model, a two-way coupling between the CA and FE models is applied. Furthermore, the effect of the fluid flow on the dendrite tip growth velocity is considered by modified dendrite tip growth kinetics. The CAFE model is applied to a quasi-2D benchmark solidification experiment of a Sn–3.0wt.%Pb alloy, and the grain structure and macrosegregation are predicted simultaneously. It is demonstrated that the model has a capacity to describe the undercooling ahead of the growth front. The growth directions of columnar grains, grain sizes, and columnar-to-equiaxed transition (CET) position are obviously modified by the fluid flow, and obvious segregated channels almost aligned with the orientations of the columnar grains are found. Qualitatively good agreement is obtained between the predicted segregation profiles and experimental measurements.

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Taylor, P. R., G. P. Martins und S. E. Clay. „Modeling of noncatalytic fluid-solid reactions: a cylindrical pellet grain model“. Mining, Metallurgy & Exploration 2, Nr. 3 (August 1985): 174–78. http://dx.doi.org/10.1007/bf03402615.

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Djavanroodi, F., Osama M. Irfan und Fahad A. Al-Mufadi. „Erosion Corrosion Behavior of Nanostructure Commercial Pure Titanium in Simulated Body Fluid“. MATEC Web of Conferences 261 (2019): 01004. http://dx.doi.org/10.1051/matecconf/201926101004.

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To date, ECAP technique have been successfully employed to produce Ultra-fine/Nanostructure grain materials, but some materials such as hexagonal closed-packed (HCP) alloys are difficult to process by ECAP at room temperature. In this work, Transmission Electron Microscopy (TEM), Vickers hardness test and Torsion test were employed to confirm the attainment of ultrafine/nanostructured grain (UFG/NSG) commercial pure titanium (CP-Ti) Titanium fabricated by ECAP as a sever plastic deformation process. The samples were pressed by ECAP (route BC) up to four passes at elevated temperature (400° C). Finally, the Erosion-Corrosion (E-C) behavior of ultrafine/nanostructured grain (UFG/NSG) Titanium in a simulated body fluid were investigated through weight loss measurement.

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Baumgarten, Aaron S., und Ken Kamrin. „A general fluid–sediment mixture model and constitutive theory validated in many flow regimes“. Journal of Fluid Mechanics 861 (28.12.2018): 721–64. http://dx.doi.org/10.1017/jfm.2018.914.

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We present a thermodynamically consistent constitutive model for fluid-saturated sediments, spanning dense to dilute regimes, developed from the basic balance laws for two-phase mixtures. The model can represent various limiting cases, such as pure fluid and dry grains. It is formulated to capture a number of key behaviours such as: (i) viscous inertial rheology of submerged wet grains under steady shearing flows, (ii) the critical state behaviour of grains, which causes granular Reynolds dilation/contraction due to shear, (iii) the change in the effective viscosity of the fluid due to the presence of suspended grains and (iv) the Darcy-like drag interaction observed in both dense and dilute mixtures, which gives rise to complex fluid–grain interactions under dilation and flow. The full constitutive model is combined with the basic equations of motion for each mixture phase and implemented in the material point method (MPM) to accurately model the coupled dynamics of the mixed system. Qualitative results show the breadth of problems which this model can address. Quantitative results demonstrate the accuracy of this model as compared with analytical limits and experimental observations of fluid and grain behaviours in inhomogeneous geometries.

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Hart, David J., und Herbert F. Wang. „Variation of unjacketed pore compressibility using Gassmann’s equation and an overdetermined set of volumetric poroelastic measurements“. GEOPHYSICS 75, Nr. 1 (Januar 2010): N9—N18. http://dx.doi.org/10.1190/1.3277664.

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Gassmann’s original equation provides a means to relate bulk elastic parameters of a porous material with the compressibility of the pore fluid. The original analysis assumed microhomogeneity and isotropy, which assumed that pore compressibility was equal to grain compressibility. Although subsequent theoretical arguments have shown that Gassmann’s original assumption is violated for most rocks and that pore compressibility need not equal grain compressibility, few experimental studies have compared the two compressibilities; the assumption that pore compressibility equals grain compressibility is still commonly made. We measured hydrostatic poroelastic constants of Berea sandstone and Indiana limestone under drained, undrained, and unjacketed conditions over a range of confining and pore pressures to test the assumption that pore compressibility equals grain compressibility. These two rocks were chosen because they havesimilar values of porosity but different elastic behaviors: Berea sandstone is nonlinearly elastic, especially at low effective stresses, but Indiana limestone is linearly elastic at nearly all stresses. At low effective stresses below [Formula: see text], the pore compressibility for Berea sandstone does not equal grain compressibility but approaches fluid compressibility. Even at higher effective stresses, pore compressibility for Berea sandstone does not equal bulk grain compressibility but approaches a value approximately two to three times the bulk grain compressibility. In contrast, pore compressibility for Indiana limestone does seem to be equal to grain compressibility except perhaps at low effective stresses below [Formula: see text]. The difference between pore compressibilities of these two rocks is likely from the presence of more compliant clay minerals mixed with quartz grains with more microcracks in the Berea sandstone as compared to the well-cemented Indiana limestone.

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Vreeman, Christopher J., J. David Schloz und Matthew John M. Krane. „Direct Chill Casting of Aluminum Alloys: Modeling and Experiments on Industrial Scale Ingots“. Journal of Heat Transfer 124, Nr. 5 (11.09.2002): 947–53. http://dx.doi.org/10.1115/1.1482089.

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A continuum mixture model of the direct chill casting process is compared to experimental results from industrial scale aluminum billets. The model, which includes the transport of free-floating solid particles, can simulate the effect of a grain refiner on macrosegregation and fluid flow. It is applied to an Al-6 wt% Cu alloy and the effect of grain refiner on macrosegregation, sump profile, and temperature fields are presented. Two 45 cm diameter billets were cast under production conditions with and without grain refiner. Temperature and composition measurements and sump profiles are compared to the numerical results. The comparison shows some agreement for the grain refined case. It is believed that an incorrect assumption about the actual grain structure prevents good agreement in the non-grain refined billet.

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Adams, David Lawson. „Toward bed state morphodynamics in gravel-bed rivers“. Progress in Physical Geography: Earth and Environment 44, Nr. 5 (30.01.2020): 700–726. http://dx.doi.org/10.1177/0309133320900924.

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In fluvial geomorphology, one of the most pervasive paradigms is that the size of the grains present in a river exercises an important effect on its character. In gravel-bed rivers, there is considerable scatter in the relations between so-called “representative grain sizes” and basic channel processes and morphologies. Under a grain size paradigm, our ability to rationalize the characteristics of a given channel and predict how it will respond to a change in conditions is limited. In this paper, I deconstruct this paradigm by exploring its historical origins in geomorphology and fluid dynamics, and identify three of its underlying premises: (1) the association between grain diameter and fluid drag derived from Nikuradse’s experiments with sand-coated surfaces; (2) the use of grain size by early process geomorphologists to describe general trends across large samples of sand-bed rivers; and (3) a classificatory approach to discerning bed structures originally developed for bed configurations found in sand-bed rivers. The conflation of sand- and gravel-bed rivers limits our ability to understand gravel-bed morphodynamics. Longstanding critique of the grain size paradigm has generated alternative ideas but, due to technological and conceptual limitations, they have remained unrealized. One such unrealized idea is the morphology-based definition of bed state – an important degree of freedom within fluvial systems, particularly in reaches where adjustments to planform are not easily achieved. By embracing recent advancements in fluid dynamics and remote sensing, I present an alternative or complementary concept of bed state based on the notion that fluvial systems act to maximize flow resistance. The proposed quantitative index represents the relative contribution of morphologic adjustments occurring at different spatial scales (discriminated using a wavelet transform) to a stable channel configuration. By explicitly acknowledging the complexity of bed adjustments we can move toward a more complete understanding of channel stability in gravel-bed rivers.

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Laibe, Guillaume, Jean-François Gonzalez, Laure Fouchet und Sarah T. Maddison. „3D SPH simulations of grain growth in protoplanetary disks“. Proceedings of the International Astronomical Union 3, S249 (Oktober 2007): 385–88. http://dx.doi.org/10.1017/s1743921308016864.

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AbstractWe present the first results of the treatment of grain growth in our 3D, two-fluid (gas+dust) SPH code describing protoplanetary disks. We implement a scheme able to reproduce the variation of grain sizes caused by a variety of physical processes and test it with the analytical expression of grain growth given by Stepinski & Valageas (1997) in simulations of a typical T Tauri disk around a one solar mass star. The results are in agreement with a turbulent growing process and validate the method. We are now able to simulate the grain growth process in a protoplanetary disk given by a more realistic physical description, currently under development. We discuss the implications of the combined effect of grain growth and dust vertical settling and radial migration on subsequent planetesimal formation.

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