3D Tomographic Transition of Particle Distribution in Microchannel

2011 ◽  
Author(s):  
Je-Eun Choi ◽  
Masahiro Takei
Keyword(s):  
Particle Concentration ◽  
Particle Distribution ◽  
Solid Phase ◽  
Flow Direction ◽  
Three Dimensional ◽  
Quantitative Result ◽  
Deionized Water ◽  
Two Phase ◽  
Cross Sectional ◽  
Reconstruction Image

The three dimensional cross-sectional particle concentrations of particle-liquid two phase flows in the two cross-seciton of microchannel has been reconstructed using process tomography. In the obtained 3D (2D space and time) reconstruction image, the dielectric particle-injected area appears to have a high particle concentration, and the deionized water-injected area appears to have a low particle concentration. Dielectric particles as the solid phase and non-conductive deionized water as the liquid phase are non-uniformly injected to the microchannel. The comparison between the qualitative result of 3D reconstruction image and the quantitative result of particle concentration in flow direction transition is that the particle is reasonably distributed in the particle injected area of the cross-section. Based on the reconstructed particle distribution image, it is easy to estimate the particle diffusion behaviors in microchannel.

scholarly journals Application of VOF and k-ε turbulence model in simulation of flow over a bottom aerated ramp and step structure

Water SA ◽  
2019 ◽  
Vol 45 (2 April) ◽  
Author(s):  
Talia Tokyay ◽  
Can Kurt
Keyword(s):  
Flow Direction ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Single Step ◽  
Air Concentration ◽  
Two Phase ◽  
Cross Sectional ◽  
Ansys Fluent ◽  
Jet Length ◽  
Logarithmic Decay

A three-dimensional numerical model of ANSYS, Fluent (2011) was employed for studying mid to high discharge supercritical two-phase flow over a single slope spillway with a single step for aeration of the flow. In this study 18 simulations were conducted using the Volume of Fluid (VOF) method for air-water interface tracking and simple k-ɛ model for turbulence closure. Submerged circular shaped pipes located at the bottom of the step were utilized as aerators. Analyses concentrate on the air-entrainment phenomenon and jet-length of the flow from the step to the re-attachment point. The variables considered in the study are discharge, aerator size, different aerator arrangements, Froude number of the flow, presence of a ramp before the step and its angle. Observed jet-length values in this study were compared with two sets of empirical formulae from literature for code validation. Cross-sectional average of air concentration due to bottom aeration was determined in the streamwise direction downstream of the re-attachment of the jet. The air concentration is observed to follow a logarithmic decay in the flow direction within the de-aeration zone.

scholarly journals Study of the Effect of Centrifugal Force on Rotor Blade Icing Process

2017 ◽  
Vol 2017 ◽  
pp. 1-9 ◽  
Author(s):  
Zhengzhi Wang ◽  
Chunling Zhu
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Force ◽  
Rotor Blade ◽  
Flow Direction ◽  
Three Dimensional ◽  
Simulation Method ◽  
Two Phase ◽  
Numerical Simulation Method ◽  
Calculation Results ◽  
Flow Field Characteristics

In view of the rotor icing problems, the influence of centrifugal force on rotor blade icing is investigated. A numerical simulation method of three-dimensional rotor blade icing is presented. Body-fitted grids around the rotor blade are generated using overlapping grid technology and rotor flow field characteristics are obtained by solving N-S equations. According to Eulerian two-phase flow, the droplet trajectories are calculated and droplet impingement characteristics are obtained. The mass and energy conservation equations of ice accretion model are established and a new calculation method of runback water mass based on shear stress and centrifugal force is proposed to simulate water flow and ice shape. The calculation results are compared with available experimental results in order to verify the correctness of the numerical simulation method. The influence of centrifugal force on rotor icing is calculated. The results show that the flow direction and distribution of liquid water on rotor surfaces change under the action of centrifugal force, which lead to the increasing of icing at the stagnation point and the decreasing of icing on both frozen limitations.

Application of Two Phase Eulerian CFD Model to Simulate High Velocity Jet Induced Scour

2020 ◽  
Author(s):  
Nicholas S. Tavouktsoglou ◽  
Aggelos Dimakopoulos ◽  
Jeremy Spearman ◽  
Richard J. S. Whitehouse
Keyword(s):  
Numerical Model ◽  
High Velocity ◽  
Stokes Equations ◽  
Solid Phase ◽  
Three Dimensional ◽  
Water Jet ◽  
Ocean Engineering ◽  
Two Phase ◽  
Water Jets ◽  
Good Agreement

Abstract Submerged water jet causing soil excavation is a typical water-soil interaction process that occurs widely in many engineering disciplines. In hydraulic engineering for instance, a typical example would be scour downstream of headcuts, culverts, or dam spillways. In port and waterway engineering, erosion of the channel bed or quay wall by the propellers of passing ships are also typical water jet/soil interaction problems. In ocean engineering, trenching by impinging high-velocity water jets has been used as an efficient method for cable and pipeline burial. At present, physical modelling and simple prediction equations have been the main practical engineering tool for evaluating scour in these situations. However, with the increasing computational power of modern computers and the development of new Computational Fluid Dynamics (CFD) solvers, scour prediction in such engineering problems has become possible. In the present work three-dimensional (3D) numerical modelling has been applied to reproduce the capability of a pair of water jets to backfill an excavated trench. The simulations are carried out using a state-of-the-art three-dimensional Eulerian two-phase scour model based on the open source CFD software OpenFOAM. The fluid phase is resolved by solving modified Navier-Stokes equations, which take into consideration the influence of the solid phase, i.e., the soil particles. This paper first presents a validation of the numerical model against vertical jet erosion tests from the literature and conducted at HR Wallingford. The results of the model show good agreement with the experimental tests, with the numerical model predicting the scour hole depth and extent with good accuracy. The paper then presents a validation of the model’s ability to reproduce deposition which is evaluated through a comparison with settling velocity data and empirical formulations found in literature, again with the model showing good agreement. Finally, the model is applied to a prototype cable burial problem using a commercially available controlled flow jet excavator. The study found that the use of water jets can be effective (subject to confirmation of the time-scale required for real operations) for performing backfill operations but that the effectiveness is closely related to the type of sediment and selection of an appropriate jet discharge. As a result, in order for the water jet method to be effective for backfill, there is a requirement for a good description of the variation in sediment type along the trench and a requirement for the jet discharge to be varied as different sediment types are encountered.

Interference in a three-dimensional array of jets

2015 ◽  
Vol 26 (5) ◽  
pp. 795-819
Author(s):  
P. E. WESTWOOD ◽  
F. T. SMITH
Keyword(s):  
Cross Sections ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Longitudinal Vortex ◽  
Cross Sectional ◽  
Dimensional Array ◽  
Unsteady Jets ◽  
The Cross ◽  
Jet Cross Sections

The theoretical investigation here of a three-dimensional array of jets of fluid (air guns) and their interference is motivated by applications to the food sorting industry especially. Three-dimensional motion without symmetry is addressed for arbitrary jet cross-sections and incident velocity profiles. Asymptotic analysis based on the comparatively long axial length scale of the configuration leads to a reduced longitudinal vortex system providing a slender flow model for the complete array response. Analytical and numerical studies, along with comparisons and asymptotic limits or checks, are presented for various cross-sectional shapes of nozzle and velocity inputs. The influences of swirl and of unsteady jets are examined. Substantial cross-flows are found to occur due to the interference. The flow solution is non-periodic in the cross-plane even if the nozzle array itself is periodic. The analysis shows that in general the bulk of the three-dimensional motion can be described simply in a cross-plane problem but the induced flow in the cross-plane is sensitively controlled by edge effects and incident conditions, a feature which applies to any of the array configurations examined. Interference readily alters the cross-flow direction and misdirects the jets. Design considerations centre on target positioning and jet swirling.

Three-Dimensional Numerical Simulation of Convective Melting of Solid Particles in a Fluid

1999 ◽  
Author(s):  
Y. L. Hao ◽  
Y.-X. Tao
Keyword(s):  
Volume Fraction ◽  
Solid Phase ◽  
Rectangular Cross Section ◽  
Three Dimensional ◽  
Phase Changes ◽  
Solid Particles ◽  
Preliminary Calculation ◽  
Two Phase ◽  
Closed Set ◽  
Gravity Effects

Abstract A physical model of two-phase flow and heat-mass transfer with the phase changes based on the theory of interacting continua is proposed. All terms in the conservation equations are analyzed and the constitutive equations are presented. A closed set of governing equations describing the convective melting of solid particles in a fluid is obtained. The numerical method is developed for the solution of velocity, temperature, and volume fraction of solid phase for the three-dimensional melting in a rectangular cross-section channel. Preliminary calculation, including gravity effects, shows that the result is reasonable. This study provides a basis for the theoretical and experimental investigation of convective melting of solid particles in a fluid.

Single-Blow Transients in Packed-Bed Storage Units With Solid-Phase Conduction by Crump’s Numerical Inversion of Laplace Transforms

1983 ◽  
Vol 105 (3) ◽  
pp. 493-497 ◽  
Author(s):  
P. -C. Lu
Keyword(s):  
Finite Difference ◽  
Linear Problem ◽  
Solid Phase ◽  
Flow Direction ◽  
Packed Bed ◽  
Laplace Transforms ◽  
Numerical Inversion ◽  
Storage Unit ◽  
Two Phase ◽  
Storage Units

A robust and fast scheme for the numerical inversion of Laplace transforms, recently established by Crump, is applied to the linear problem of two-phase (solid-and-fluid) response of a packed-bed thermal storage unit during a single-blow operation, with solid conduction in the flow direction properly considered (while neglecting the conduction and energy storage in the fluid). The scheme is shown to be capable of handling implicit solutions in the transformed domain, which are themselves to be calculated numerically on a computer. The numerical results compare very well with those obtained by other methods of attack. The comparison also discloses some rather large errors in a set of data generated by a finite difference scheme as reported in the literature.

scholarly journals Growth model for large branched three-dimensional hydraulic crack system in gas or oil shale

2016 ◽  
Vol 374 (2078) ◽  
pp. 20150418 ◽  
Author(s):  
Viet T. Chau ◽  
Zdeněk P. Bažant ◽  
Yewang Su
Keyword(s):  
Solid Phase ◽  
Three Dimensional ◽  
Cohesive Crack ◽  
Rock Joints ◽  
Recent Analysis ◽  
Band Model ◽  
Two Phase ◽  
Strength Limit ◽  
Crack Wall ◽  
Phase Medium

Recent analysis of gas outflow histories at wellheads shows that the hydraulic crack spacing must be of the order of 0.1 m (rather than 1 m or 10 m). Consequently, the existing models, limited to one or several cracks, are unrealistic. The reality is 10 5 –10 6 almost vertical hydraulic cracks per fracking stage. Here, we study the growth of two intersecting near-orthogonal systems of parallel hydraulic cracks spaced at 0.1 m, preferably following pre-existing rock joints. One key idea is that, to model lateral cracks branching from a primary crack wall, crack pressurization, by viscous Poiseuille-type flow, of compressible (proppant-laden) frac water must be complemented with the pressurization of a sufficient volume of micropores and microcracks by Darcy-type water diffusion into the shale, to generate tension along existing crack walls, overcoming the strength limit of the cohesive-crack or crack-band model. A second key idea is that enforcing the equilibrium of stresses in cracks, pores and water, with the generation of tension in the solid phase, requires a new three-phase medium concept, which is transitional between Biot’s two-phase medium and Terzaghi’s effective stress and introduces the loading of the solid by pressure gradients of diffusing pore water. A computer program, combining finite elements for deformation and fracture with volume elements for water flow, is developed to validate the new model. This article is part of the themed issue ‘Energy and the subsurface’.

Three-Dimensional Numerical Simulation of Fluid with Sparse Particles' Erosion to Pipelines

2013 ◽  
Vol 805-806 ◽  
pp. 1785-1789
Author(s):  
Chang Bin Wang ◽  
Miao Wang ◽  
Xiao Xu Li ◽  
Yu Liu ◽  
Jie Nan Dong
Keyword(s):  
Fluid Dynamics ◽  
Numerical Simulation ◽  
Flow Model ◽  
Particle Distribution ◽  
Three Dimensional ◽  
Two Phase ◽  
Wear Area ◽  
Computational Fluid Dynamics Cfd ◽  
Set Up ◽  
Volume Method

A three dimensional fluid flow model was set up in this paper, based on the computational fluid dynamics (CFD) and the elasticity theory. Using the finite volume method, a 120° bend was taken as a research object to simulate the erosion to the wall of fluid with sparse particles, finally, to determine the most severe wear areas.At the same time, the distribution of two-phase flows pressure and velocity was analyzed in 45° and 90° bends, then tracked the trajectory of the particles. The results show that the 90°bend has the smallest wear area and particle distribution or combination property is the best.

An Efficient CFD Model for Air/Particle Saltating Flows

2002 ◽  
Author(s):  
S. Ji ◽  
A. G. Gerber ◽  
A. C. M. Sousa
Keyword(s):  
Particle Concentration ◽  
Particle Surface ◽  
Three Dimensional ◽  
Phase System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Dynamics Model ◽  
Three Dimensional Flow ◽  
Two Phase ◽  
Wide Range

The study reports on the development of a computational-fluid-dynamics model is presented suitable for computationally efficient evaluation of particle transport along loose surfaces. These surfaces can be described within the context of an interaction with a two-phase air/particle mixture in a state of combined suspension and saltation. The results suggest an approach for approximating the two-phase system with coupling to a moving surface, along with the inclusion of impact and entrainment fluxes at the surface that is generally extendable to a wide range of particle/surface conditions. The model results are compared to available experimental data on particle concentration profiles along saltating surfaces, and applied to geometry involving complex three-dimensional flow to show the generality of the approach.

scholarly journals Optimizing the cleanliness in multi-segment disk amplifiers based on vector flow schemes

2018 ◽  
Vol 6 ◽  
Author(s):  
Zhiyuan Ren ◽  
Jianqiang Zhu ◽  
Zhigang Liu ◽  
Xiaowei Yang
Keyword(s):  
Flow Field ◽  
Particle Concentration ◽  
Flow Model ◽  
Three Dimensional ◽  
Phase Flow ◽  
Three Dimensional Flow ◽  
Two Phase ◽  
Key Factor ◽  
Measurement Experiment ◽  
Laser Induced Damage

The objective of maintaining the cleanliness of the multi-segment disk amplifier in Shenguang-II (SG-II) is to reduce laser-induced damage for optics. The flow field of clean gas, which is used for the transportation of contaminant particles, is a key factor affecting the cleanliness level in the multi-segment disk amplifier. We developed a gas–solid coupling and three-dimensional flow numerical simulation model. The three-dimensional and two-phase flow model is verified by the flow-field smog experiment and the particle concentration measurement experiment with the 130-disk amplifier in SG-II. By optimizing the boundary conditions with the same flow rate, the multi-inlet vector flow scheme can not only effectively reduce the purging time, but also prevent the reverse diffusion of contaminant particles in the multi-segment disk amplifier and the deposition of contaminant particles on the surface of the Nd:glass.

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