Top PDF On the transport properties of fluid-particle flow

On the transport properties of fluid-particle flow

On the transport properties of fluid-particle flow

The case of steady-state thermal conductiv ' ity of bulk fluid has been d ealt with. Here, it is intended to generalize the result above to unsteady thermal conduction[r]

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Particle transport in a pulmonary flow

Particle transport in a pulmonary flow

The study undertaken in this article is to develop a reliable and comprehensive numerical modelling of particle transport in pulmonary flow based on the use of CFD-ACE code of commercial calculation. This code includes a fluid solver that solves the Navier-Stokes in a finite volume formulation. The CFD-GEOM software was used to create the 3D surfaces of the generic model geometry Weibel and thereby generate the tetrahedral mesh unstructured finite volume. The air flow is assumed laminar stationary (or unsteady only in bronchial models) and incompressible, the particles of diameter 5 micrometers are spherical and non-interacting. So we have successfully modelled the flows and the transport of particles in simple configurations (Model Weibel) and realistic configuration (rat lung) and what we can say is that the simulation , although expensive in terms of computer memory and time (specially for particle deposition), does not present insurmountable difficulties. As against obtaining a realistic geometry and the associated mesh generation remains a delicate stage.
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Fluid-particle interaction in geophysical flows: debris flow

Fluid-particle interaction in geophysical flows: debris flow

Chapter 6 Conclusions This work describes small scale laboratory debris flow experiments. These experi- ments were carried out using both dry glass beads and glass beads in mixtures of water or glycerol, which were released from behind a lock gate to flow down an inclined flume. The main objective was to gain a better understanding of how fluid- particle interaction determines dynamic morphological features under the influence of particle size, roughness element diameter, interstitial fluid viscosity and solid volume fraction. The design base of the physical model was after Froude and Reyn- olds particle number scaling similarity criteria to achieve dynamic similarity with full-scale debris flows, to ensure that gravity forces are correctly scaled and turbu- lent fluid-particle interaction. A statistical method based on the standard deviation from the local average velocities obtained from the Particle Image Velocimetry tech- nique allowed systematically to define of the characteristic front position and of flow height. Low and high deviation from the local mean define the two co-existent re- gimes of non-fluctuating and intermittent collisional regions, define by the low and high deviation from the local mean, showed the influence of flow composition and roughness element diameter.
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Some Features of Flow and Particle Transport in Porous Structures

Some Features of Flow and Particle Transport in Porous Structures

Porous filters have been used for removing particles with success for many years [4]. Their wide application in air pollution control and in different technologies is due to their reliability in the separation of particles and relatively low operating cost. One of the most important issues in filtration is to know how media’s physical properties varied during operating conditions. Filter’s collectors (microscopic scale) are properly designed if, during a reasonably long filtering operation, filter’s collection efficiency is high and media’s flow resistance is below assumed value [5-6]. Description of flow field
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The impact of coupling and particle volume fraction on fluid-particle interactions in a turbulent channel flow

The impact of coupling and particle volume fraction on fluid-particle interactions in a turbulent channel flow

Abstract. Direct numerical simulation, facilitated by a spectral element method, is used to predict a multi-phase fluid flow through a channel at a shear Reynolds number of 300. Following validation of single- and multi-phase flow results against other DNS predictions available in the literature, a channel flow is simulated utilising a Lagrangian particle tracker to model 300,000 particles with a diameter of 100 m, having a density ratio equivalent to that of water to glass, and a particle volume fraction of approximately 0.01%. This flow is calculated using multiple levels of coupling between the particles and the flow; one-way, two-way and four-way. The mean streamwise velocity of the fluid and the particles, along with the shear and normal stresses, are compared for the different coupling methods, with the differences between them analysed and, although small, they are found to be consistent across the channel. A second set of runs is performed using in excess of 2 million particles in order to facilitate a tenfold increase in the particle volume fraction, to 0.1%, with the particles expected in this case to have a greater impact upon the properties of the fluid. The statistics of the fluid and particles in these simulations are then compared with those from the simulation with a lower concentration of particles in order to determine the magnitude of the effect the particles have on the fluid in this flow. The effects of the different couplings on the flow are much greater in this case due to the increased number of particles affecting the flow. Also, the presence of the particles is seen to increase the turbulence levels of the fluid, especially in the streamwise direction. The accuracy of the simulations clearly increases with the level of coupling. However, the speed of the simulations decreases. One way of achieving decreased run times, for both volume fraction cases, is to use a faster stochastic version of the particle tracking code for four-way coupling.
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Transport Phenomena (Newtonian Fluid Flow in a Falling Film)

Transport Phenomena (Newtonian Fluid Flow in a Falling Film)

Consider a Newtonian liquid (of viscosity Consider a Newtonian liquid (of viscosity μ μ and density and density ρ ρ ) in laminar flow down an ) in laminar flow down an inclined flat plate of length inclined flat plate of length L L and width and width W W . The liquid flows as a falling film with . The liquid flows as a falling film with

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Microstructural and fluid transport properties of potatoes during frying

Microstructural and fluid transport properties of potatoes during frying

uid to move rapidly. Permeability is aected by the nature of porous material and owing uid, and factors like temperature, oil content, moisture content, gas content etc. A porous food matrix consists of interconnected pores through, which uid can move (Datta, 2007). During frying of a porous food matrix, like potato, moisture, oil and heat transport occur with temperature and pressure changing spatially and temporally. Initially, the pressure increases rapidly after immersing the potato samples into the hot oil for frying. As potato discs contain higher moisture content in the beginning, the pressure rise is high initially due to rapid evaporation and build up of pressure (Sandhu, Bansal, & Takhar, 2013b). Later, the vapors escape the matrix and cause negative pressure inside the potato structure due to matrix's suction potential and capillary eects. The negative pressure causes increase of oil uptake during frying. After frying, when the cooling starts, the pressure decreases further.
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Detailed modelling of fluid-particle interaction in sediment transport with applications in rivers

Detailed modelling of fluid-particle interaction in sediment transport with applications in rivers

The study of flow in open channels in a physical and mathematical approach started by Leonardo Da Vinci in 1500, the Italian experimentalist and engineer who showed eddies in his art sketches. This great interest of water motion was then carried out by another scientist Galileo Galilei through experiments. Galileo‘s student, Benedetto Castelli, who explained the continuity law in more details in his book in 1628, was credited as being the founder of river hydraulics afterward. Later on in the seventeenth century, Sir Isaac Newton introduced the law of viscosity where the proportionality of shear stress and the velocity gradient was stated in his proposal. Newton‘s work was continued by Prandtl where the shear stress relationship was used to create assumptions for turbulent flows. However in the eighteenth century, Daniel Bernoulli and Leonard Euler derived mathematical description of fluid mechanics, the excellence of equations were not to its maximum until Navier-Stokes equations (N-S) were derived by Claude-Louis Navier in 1822 and George Stokes in 1845 (Graf 1984; Anderson Jr 2005; Wright and Crosato 2011).
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Modelling Fluid Flow and Heat Transport in Fractured Porous Media

Modelling Fluid Flow and Heat Transport in Fractured Porous Media

In the strive for more accurate models, we can for instance take into consideration fissures or fractures which may have been formed in a porous rock. A rock under stress has a possibility of cracking up, and fractures of far greater diameter and much straighter than the intricate pore network might arise. Intuitively, depending on the amount of fracturing, this can be a considerable factor when describing how a fluid flows through the rock, both when it comes to the fluid velocity and the preferential paths of the fluid. We will look closer at how we can include the effects of fractures when modelling a porous medium. We will examine both the movement of the fluid and the heat transfer processes that occur. Some fracture model comparisons have been made earlier, see for instance [55] where they take a closer look at three different models for flow and solute transport.
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Reactive transport and fluid pathways in fracture controlled flow systems

Reactive transport and fluid pathways in fracture controlled flow systems

up-section trends o f O-enrichment in vein calcite indicate dominantly upwards fluid transport in both systems. Across-strike around the D A B Fault, the most strongly "'O-deplet[r]

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Direct particle fluid simulation of flushing flow in electrical discharge machining

Direct particle fluid simulation of flushing flow in electrical discharge machining

a Institute of Aerodynamics, RWTH Aachen University, Aachen, Germany; b JARA Center for Simulation and Data Science, RWTH Aachen University, Aachen, Germany ABSTRACT The efficient removal of material debris by flushing is critical for the performance and the surface quality of the electrical discharge machining (EDM) manufacturing process. The particle concentra- tion alters the thermal, mechanical, and electrical properties of the particle–dielectricum suspension and affects the manufacturing process and the surface quality by inducing high thermal loads. For the first time, we perform a direct particlefluid simulation of the flushing cycle in a generic EDM cavity using a hierarchical Cartesian sharp-interface cut-cell method. The flow around each debris particle is completely resolved and the heat transfer between the particles and the fluid is taken into account. The rate of material removal and the cooling performance of the flushing mechanism are studied for three-volume loadings. The results show that the flow around the particles has a pro- nounced impact on the heat transfer between the dielectricum and the workpiece. A particle loading of 14% increases the mean heat transfer by approximately 16%. The particle loading also has a pro- nounced impact on the rate at which particles are flushed out of the cavity. Increasing the initial volume loading from 6% to 14% decreases the amount of particles that get flushed out of the cavity by 14%.
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Computationally Efficient Simulation of Fluid-Particle Flow in Elastic Bifurcating Systems.

Computationally Efficient Simulation of Fluid-Particle Flow in Elastic Bifurcating Systems.

The objective of this thesis is to develop for tumor-targeting in the hepatic artery system a 1-D model to predict pressure and flow rate, wall distensibility, and drug-particle trajectories. Several models for computing pressure fields and flow rates exist in the literature. A general model developed by Olufsen et al. (2000), consisting of a non-linear hyperbolic system of equations, was selected for FORTRAN 95 coding in the MATLAB environment. An algebraic pressure-area relationship was used for the fluid-structure interaction. A three-element Windkessel model was employed as the outlet boundary condition, while the flow conditions were specified at the inlet. Validations were accomplished for the cases of a single flexible bifurcation, a flexible tube with physiological inflow, a representative model of the aorta and 3-D simulations of the hepatic arterial system.
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An integrated particle model for fluid–particle–structure interaction problems with free-surface flow and structural failure

An integrated particle model for fluid–particle–structure interaction problems with free-surface flow and structural failure

Fig.7 Boundary treatments in SPH and DEM 6. Implementation and computational flowchart The overall algorithm process is depicted in Fig.8. First of all, particle elements and boundaries are generated under initial conditions. Once the simulation begins, each particle element searches its surrounding particle elements through the linked-list scheme and interaction forces are computed. For structure particle elements, they are subjected to hydrodynamic forces from fluid particle elements, direct contact forces from solid particle elements and inherent bond forces from themselves. The bond forces determine the breakage of the bond if the excess of tensile strength is reached. The fluid particle elements are not only subjected to hydrodynamic forces but also under the reaction forces (e.g. drag forces and buoyancy forces) from solid particle elements using the technique of Shepard filter. In addition, to drag forces and buoyancy forces from fluid particle elements, direct contact forces also exist among solid particle elements. In terms of boundary treatment, boundary particle elements are specific for SPH particle elements through SPH algorithm. On the other hand, boundary lines work for DEM particle elements according to the linear contact model when DEM particle elements approaching to boundaries. After the calculations of interaction forces acting on each particle elements, its position, velocity and density are updated at each time step until the end of calculation.
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Physically Based Preconditioning Techniques Applied to the First Order Particle Transport and to Fluid Transport in Porous Media

Physically Based Preconditioning Techniques Applied to the First Order Particle Transport and to Fluid Transport in Porous Media

The physically based preconditioner is applied to each of these linear solvers with good improvements in efficiency in each case. The term physically based preconditioner used here refers to the fact that the preconditioners used in this study are based on the physical nature or physics of the problem being studied. In the case of particle transport, the linear system structure has a block structure due to the various angles that a particle may scatter when encountering a given point in a material. The preconditioner for the linear systems from the finite element methods for the first order transport equation is derived from the equation itself. More specifically, the preconditioner used is the system matrix that would be obtained if there were no scattering present. For each of the specific problems studied, the physically based preconditioner is compared with several algebraic preconditioners including some of those mentioned earlier like the Jacobi method and successive over-relaxation.
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THEORETICAL SCHEME FOR TRANSPORT PROPERTIES OF LENNARD-JONES FLUID MIXTURES

THEORETICAL SCHEME FOR TRANSPORT PROPERTIES OF LENNARD-JONES FLUID MIXTURES

Post Graduate Department of Physics, L.S. College, B.R.A. Bihar University, Muzaffarpur-842001. Abstract : Using Molecular dynamics to compute the transport properties of Lennard-Jones fluid mixtures using Green-Kubo formula. This formula is applied to estimate the transport properties (TP's) such as shear viscosity and thermal inductivity of Ar-Kr. The theory provides good result in low density regime where this experimental data and simulation is found very good.

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Pages From Reservoir Rock Properties and Fluid Flow-6425a9aeb1626f470f74a38ddbc798af

Pages From Reservoir Rock Properties and Fluid Flow-6425a9aeb1626f470f74a38ddbc798af

These classifications are essentially based upon the properties exhibited by the crude oil, including physical properties, composition, gas-oil ratio, appearance, and pressure-temperature phase diagrams: 1. Ordinary Black Oil. A typical pressure-temperature phase diagram for ordinary black oil is shown in Figure 1-2. It should be noted that quality lines, which are approximately equally spaced, characterize

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Improvement of Calculation Stability for Slow Fluid Flow Analysis Using Particle Method

Improvement of Calculation Stability for Slow Fluid Flow Analysis Using Particle Method

However, the particle methods have still some problems. Calculation stability is one of the significant problems in the particle methods. Casting process involves a variety of phe- nomena which occur simultaneously from the pouring to the solidification. Because it is difficult to expect what kind of phenomena will occur at where and at which timing, higher calculation stability is required for the integrated simulation using particle methods. It is known that the oscillation of ve- locity and pressure occurs in the flow simulation, and the os- cillation decreases the calculation stability especially for a slow flow 5) . Hirata et al. have proposed a stable and rapid calculation method for the slow flow by ignoring inertia force and adjusting the gravitational force after the fluid flow can be assumed to be almost stopped 5) . However, the procedure requires precise estimation of the flow stop time. The original flow calculation by the particle method 3) is unstable for the slow fluid flow. Therefore the flow calculation without any improvement will decrease the calculation stability when the flow becomes slow during the casting processes. Recently, Hirata et al. reported the multiple relaxation method which improves calculation stability and speed 6) in the case of slow
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Flow and conduit formation in the external fluid transport system of a suspension feeder

Flow and conduit formation in the external fluid transport system of a suspension feeder

Relationships between flow and chimney formation In this study, chimneys formed at regions with high excurrent flow speeds, as predicted by the hypothesis that high flow speed induces conduit formation in this system. The relationship between flow and conduit formation has been addressed in several internal fluid-transport systems, in which fluid moves through pipe-like conduits to transport material within the organism. Increased flow is correlated with conduit formation or increased conduit size in the vertebrate circulatory system (Brown and Hudlicka, 2003; Langille, 1995; Prior et al., 2004), the gastrovascular canals of hydroid colonies (Buss, 2001; Dudgeon and Buss, 1996) and the veins of plasmodial slime molds (Nakagaki et al., 2000). This study suggests that similar relationships between flow and conduit formation also exist in external fluid-transport systems. Unlike systems studied previously, this system is involved in suspension feeding rather than internal transport, and its conduits (the chimneys) are simple openings rather than pipes.
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Flow structures and fluid transport for the hydromedusae Sarsia
tubulosa and Aequorea victoria

Flow structures and fluid transport for the hydromedusae Sarsia tubulosa and Aequorea victoria

In the present study, we present the Lagrangian coherent structures (LCS) seen in the results of numerical simulations of hydromedusae swimming as well as several examples of particle motion in the resulting flow. The hydromedusae examined are Aequorea victoria Murbach and Shearer 1902, a paddling or rowing type of hydromedusa, and Sarsia tubulosa M. Sars 1835, a jetting type of hydromedusa. We believe this to be the first numerical study of this type. The actual motion of the hydromedusa, reproduced from digitized videos of the swimming hydromedusae, is used to compute the surrounding velocity field. A brief description of the numerical method for computing the velocity field is included in Materials and methods. The use of computational fluid dynamics (CFD) data instead of an empirical velocity field from digital particle image velocimetry (DPIV), or similar, results in higher resolution of the LCS as well as greater accuracy in subsequent calculations. Additionally, there are significant difficulties in obtaining high-quality results from DPIV for swimming hydromedusae. DPIV results are only available for the time during which the hydromedusa is properly oriented within the field of view, perhaps only a few swimming cycles depending on many factors. Additionally, the resolution obtained from DPIV depends on the concentration of particles in a given region. In general, the distribution of particles may be highly non-uniform. The particles will be drawn toward certain flow structures, just as dye is drawn into vortices in dye visualization experiments, but other areas of the flow may be left with few particles. None of these difficulties are present in our method. It is only necessary to capture a good swimming cycle. The periodic swimming motion may then be determined up to the resolution of the camera used and iterated for as many swimming cycles as desired.
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Unsteady convective boundary layer flow of a viscous fluid at a vertical surface with variable fluid properties

Unsteady convective boundary layer flow of a viscous fluid at a vertical surface with variable fluid properties

© 2012 Elsevier Ltd. All rights reserved. 1. Introduction The study of two-dimensional boundary layer flow and heat transfer induced by continuous stretching and heated surfaces has acquired momentum due to its various applications in engineering/industrial disciplines. These applications include extrusion processes, wire and fiber coating, polymer processing, food-stuff processing, design of heat exchangers, and chemical processing equipment. The concept of continuous stretching will bring in a unidirectional orientation to the extrudate; consequently the quality of the final product considerably depends on the flow and heat transfer mechanism. To that end, the analysis of momentum and thermal transports within the fluid on a continuously stretching surface is important for gaining some fundamental understanding of such processes. Sakiadis [ 1 ] was the first amongst others to initiate such a problem by considering the boundary layer fluid flow over a continuous solid surface moving with constant velocity. The thermal behavior of the problem was studied by Erickson et al. [ 2 ], and experimentally verified by Tsou et al. [ 3 ]. Crane [ 4 ] extended the work of Sakiadis [ 1 ] to the flow caused by an elastic sheet moving in its own plane with a velocity varying linearly with the distance from a fixed point. Also, heat and mass transfer aspects with Newtonian/non-Newtonian fluids are studied by several authors [ 5–11 ] under different physical situations.
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