scholarly journals An Investigation of the Effects of Volume Fraction on Drag Coefficient of Non-Spherical Particles Using PR-DNS

2021 ◽  
Author(s):  
Pratik Mahyawansi ◽  
Cheng-Xian Lin
Keyword(s):  
Drag Coefficient ◽  
Cfd Simulation ◽  
Volume Fraction ◽  
Fixed Bed ◽  
Reynold Number ◽  
High Volume ◽  
Momentum Equation ◽  
Spherical Particles ◽  
Computational Time ◽  
The Impact

Abstract Prediction of the drag coefficient is required in gas-particle multiphase flow modeling and simulation. Experimental data and correlations on the fixed-bed system of spherical particles with high volume fractions for various possible arrangements are available in the literature. However, the effect of volume fraction on the drag coefficient of non-spherical particles is not well studied. In solving the momentum equation, the volume fraction plays a vital role in determining the flow resistances. In this paper, we study the impact of volume fraction in the range of 0.069 to 0.65 on the drag coefficient using the computational fluid dynamics (CFD) simulation of air for Reynold number in the range of 10 to 10000 using particle resolved direct numerical solution (PR-DNS). Regular non-spherical particles such as a cube, tetrahedron, and spheroids are used in this study since their single particle’s drag coefficient data are available in the literature for comparison. For this work, the simulations are carried out in the Ansys Fluent using polyhedral mesh, which consumes significantly less computational time and power. The study showed the sphericity and volume fraction have significant impact on the bed pressure drop and average drag coefficient of the particles in the bed especially in high Reynolds number regime. The bed of the spheroid experiences the lowest drag being the most streamlined particle, and the particles with the edges result in a large drag coefficient due to flow separation at the discontinuity. The vector plots verify this behavior where large wake regions are observed behind the tetrahedron particle.

scholarly journals The Impact of Sinusoidal Surface Temperature on the Natural Convective Flow of a Ferrofluid along a Vertical Plate

Mathematics ◽  
2019 ◽  
Vol 7 (11) ◽  
pp. 1014 ◽  
Author(s):  
Essam R. EL-Zahar ◽  
Ahmed M. Rashad ◽  
Laila F. Seddek
Keyword(s):  
Magnetic Field ◽  
Nusselt Number ◽  
Surface Temperature ◽  
Drag Coefficient ◽  
Volume Fraction ◽  
Differential Quadrature Method ◽  
Grid Points ◽  
The Impact ◽  
Sinusoidal Surface ◽  
The Magnetic Field

The spotlight of this investigation is primarily the effectiveness of the magnetic field on the natural convective for a Fe3O4 ferrofluid flow over a vertical radiate plate using streamwise sinusoidal variation in surface temperature. The energy equation is reduplicated by interpolating the non-linear radiation effectiveness. The original equations describing the ferrofluid motion and energy are converted into non-dimensional equations and solved numerically using a new hybrid linearization-differential quadrature method (HLDQM). HLDQM is a high order semi-analytical numerical method that results in analytical solutions in η -direction, and so the solutions are valid overall in the η domain, not only at grid points. The dimensionless velocity and temperature curves are elaborated. Furthermore, the engineering curiosity of the drag coefficient and local Nusselt number are debated and sketched in view of various emerging parameters. The analyzed numerical results display that applying the magnetic field to the ferroliquid generates a dragging force that diminishes the ferrofluid velocity, whereas it is found to boost the temperature curves. Furthermore, the drag coefficient sufficiently minifies, while an evolution in the heat transfer rate occurs as nanoparticle volume fraction builds. Additionally, the augmentation in temperature ratio parameter signifies a considerable growth in the drag coefficient and Nusselt number. The current theoretical investigation may be beneficial in manufacturing processes, development of transport of energy, and heat resources.

scholarly journals Microstructural Evolution and Strengthening Mechanism of SiC/Al Composites Fabricated by a Liquid-Pressing Process and Heat Treatment

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3374 ◽  
Author(s):  
Sangmin Shin ◽  
Seungchan Cho ◽  
Donghyun Lee ◽  
Yangdo Kim ◽  
Sang-Bok Lee ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Compressive Strength ◽  
Microstructural Evolution ◽  
Load Transfer ◽  
Volume Fraction ◽  
High Volume ◽  
Strengthening Mechanism ◽  
Spherical Particles ◽  
Pressing Process ◽  
Liquid Pressing Process

Aluminum alloy (Al7075) composites reinforced with a high volume fraction of silicon carbide (SiC) were produced by a liquid-pressing process. The characterization of their microstructure showed that SiC particles corresponding to a volume fraction greater than 60% were uniformly distributed in the composite, and Mg2Si precipitates were present at the interface between the matrix and the reinforcement. A superior compressive strength (1130 MPa) was obtained by an effective load transfer to the hard ceramic particles. After solution heat treatment and artificial aging, the Mg2Si precipitates decomposed from rod-shaped large particles to smaller spherical particles, which led to an increase of the compressive strength by more than 200 MPa. The strengthening mechanism is discussed on the basis of the observed microstructural evolution.

scholarly journals Homotopy Semi-Numerical Modeling of Non-Newtonian Nanofluid Transport External to Multiple Geometries Using a Revised Buongiorno Model

Inventions ◽  
2019 ◽  
Vol 4 (4) ◽  
pp. 54 ◽  
Author(s):  
Atul Kumar Ray ◽  
Buddakkagari Vasu ◽  
O. Anwar Bég ◽  
Rama S.R. Gorla ◽  
P.V.S.N. Murthy
Keyword(s):  
Wall Temperature ◽  
Volume Fraction ◽  
Convective Boundary Condition ◽  
Computational Time ◽  
Nanoparticle Volume Fraction ◽  
Convective Boundary ◽  
Power Series Method ◽  
Fiber Technology ◽  
Buongiorno Model ◽  
The Impact

A semi-analytical solution for the convection of a power-law nanofluid external to three different geometries (i.e., cone, wedge and plate), subject to convective boundary condition is presented. A revised Buongiorno model is employed for the nanofluid transport over the various geometries with variable wall temperature and nanoparticle concentration conditions (non-isothermal and non-iso-solutal). Wall transpiration is included. The dimensional governing equations comprising the conservation of mass, momentum, energy and nanoparticle volume fraction are transformed to dimensionless form using appropriate transformations. The transformed equations are solved using a robust semi-analytical power series method known as the Homotopy analysis method (HAM). The convergence and validation of the series solutions is considered in detail. The variation of order of the approximation and computational time with respect to residual errors for temperature for the different geometries is also elaborated. The influence of thermophysical parameters such as wall temperature parameter, wall concentration parameter for nanofluid, Biot number, thermophoresis parameter, Brownian motion parameter and suction/blowing parameter on the velocity, temperature and nanoparticle volume fraction is visualized graphically and tabulated. The impact of these parameters on the engineering design functions, e.g., coefficient of skin fraction factor, Nusselt number and Sherwood number is also shown in tabular form. The outcomes are compared with the existing results from the literature to validate the study. It is found that thermal and solute Grashof numbers both significantly enhance the flow velocity whereas they suppress the temperature and nanoparticle volume fraction for the three different configurations, i.e., cone, wedge and plate. Furthermore, the thermal and concentration boundary layers are more dramatically modified for the wedge case, as compared to the plate and cone. This study has substantial applications in polymer engineering coating processes, fiber technology and nanoscale materials processing systems.

scholarly journals Mathematical Modelling for Effects of Fineness Ratio, Altitude and Velocity on Aerodynamic Characteristics of an Airship Design using Computational Analysis

CFD letters ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 90-110
Author(s):  
Jafirdaus Jalasabri ◽  
Fairuz Izzuddin Romli ◽  
Mohammad Yazdi Harmin
Keyword(s):  
Regression Model ◽  
Drag Coefficient ◽  
Goodness Of Fit ◽  
Cfd Simulation ◽  
Predictive Accuracy ◽  
Lift Coefficient ◽  
Research Work ◽  
Aerodynamic Performance ◽  
The Other ◽  
The Impact

The external shape design change of an airship can be appropriately captured by design fineness ratio, which is defined as the ratio of airship's length to its maximum width. However, there is a lack of aerodynamic models that have been established for airship design purposes. In conjunction to this realization, the aim of this research work is to establish the effects of design fineness ratio of an airship towards its aerodynamic performance. The Atlant-100 airship is chosen as the reference design model for this study. In total, 36 simulation runs are executed with different combinations of values for the fineness ratio, altitude and velocity. The obtained CFD simulation results are then statistically analysed using Minitab software to evaluate the significance of the design fineness ratio effects. From the results, it has been found that smaller fineness ratio corresponds to higher aerodynamic lift and drag forces. As in the case simulated in this study, the smallest fineness ratio of 0.93 has been shown to correspond to the highest value of generated lift coefficient while having comparable value of generated drag coefficient with the other fineness ratios. This highlights that a smaller fineness ratio of the airship design is more suitable. The constructed mathematical models to capture these effects have also been validated with a few goodness-of-fit tests. For the regression model of fineness ratio impact on the lift coefficient, it has R2 value of 0.941. When its predictive accuracy is tested with few simulated random cases, the maximum error obtained is only 6%. On the other hand, for the regression model of the fineness ratio impact on drag coefficient, the R2 value is 0.962 and maximum predictive error from the simulation random cases test is only 9%. Overall, it can be concluded that the constructed regression models have good predictive capability on the impact of design fineness ratio on the aerodynamic performance of the airship under this study.

Heat transfer to a slowly moving fluid from a dilute fixed bed of heated spheres

1980 ◽  
Vol 101 (2) ◽  
pp. 403-421 ◽  
Author(s):  
A. Acrivos ◽  
E. J. Hinch ◽  
D. J. Jeffrey
Keyword(s):  
Temperature Gradient ◽  
Volume Fraction ◽  
Fixed Bed ◽  
Spherical Particles ◽  
Excess Temperature ◽  
Bulk Heating ◽  
Averaged Equations ◽  
Significant Temperature ◽  
The Difference ◽  
Sufficient Magnitude

Using the method of averaged equations, we examine the difference in temperature between the bulk and fixed heated spherical particles under conditions in which ϕ the volume fraction of the particles and ε the Peclet number of the flow past the particles are both small. If ϕ [Lt ] ε2 the particles are effectively isolated, and so their excess temperature has an O(ε) correction to the pure conduction estimate. On the other hand if ϕ [Gt ] ε2, the bulk heating is of sufficient magnitude to produce a significant temperature gradient throughout the fixed bed. This temperature gradient leads to an O(ϕ½) correction to the pure conduction estimate of the excess temperature of the particles, and the correction depends on the details of the flow even though its magnitude is independent of ε. A study of the leading-order terms when ϕ and ε2 are of the same magnitude finds that the two small effects are not simply additive.

Numerical prediction of thermal conductivity in ZrB2-particulate-reinforced epoxy composites based on finite element models

2018 ◽  
Vol 25 (2) ◽  
pp. 337-342
Author(s):  
Yicheng Wu ◽  
Zhiqiang Yu
Keyword(s):  
Thermal Conductivity ◽  
Finite Element ◽  
Volume Fraction ◽  
High Volume ◽  
Epoxy Composites ◽  
Spherical Particles ◽  
Homogeneous Distribution ◽  
Finite Element Models ◽  
Negative Effect ◽  
Thermal Conductivities

AbstractEpoxy composites reinforced by Zirconium diboride (ZrB2) particles were investigated by finite element models (FEMs). It helped to explore the relationship between the thermal conductivity of composites and the volume fraction, size, shape, orientation, and arrangement of the ZrB2particles. The results showed that the thermal conductivity performance of composites was improved effectively when filled with ZrB2particles. Specifically, epoxy composites filled with 50 vol% spherical ZrB2particles had 12.05 times the thermal conductivity of epoxy resin. At the same volume fraction, the number of ZrB2particles in the epoxy matrix has little influence on thermal conductivity due to the dimensionless models. At a high volume fraction, rectangular ZrB2particles improved thermal conductivity more effectively than spherical particles. In the comparison of thermal conductivities among composites reinforced by rectangular fillers, the thermal conductivities of composites were clearly affected by the length-width ratios of fillers, and this effect was monotonically increasing. The vertical orientations of particles could conduct heat most effectively compared with slant and parallel orientations. The agglomerate distribution of ZrB2particles has the negative effect of thermal diffusion in a certain direction compared with homogeneous distribution.

Enhanced thermal conductivity of epoxy/alumina composite through multiscale-disperse packing

2020 ◽  
Vol 55 (1) ◽  
pp. 17-25
Author(s):  
Hongkun Li ◽  
Weidong Zheng
Keyword(s):  
Thermal Conductivity ◽  
Volume Fraction ◽  
Mean Field ◽  
High Volume ◽  
Theory Model ◽  
Spherical Particles ◽  
Particle Sizes ◽  
Interfacial Resistance ◽  
Steady State Method ◽  
Cure Shrinkage

Inspired by the size of the voids in closest packing structures, we propose to use the combination of spherical particles with different size scales to increase the loading fraction of the fillers in epoxy-based composites. In this study, high loading up to 79 vol% has been achieved with multiscale particle sizes of spherical Al2O3 particles. The highest thermal conductivity of Al2O3-filled liquid epoxy measured by steady-state method is 6.7 W m−1 K−1 at 25°C, which is approximately 23 times higher than the neat epoxy (0.28 W m−1 K−1). Three models based on Maxwell mean-field scheme (MMF), differential effective medium (DEM) and percolation theory model (PTM) were utilized to assess our measured thermal conductivity data. We found that both DEM and PTM models could give good results at high volume fraction regime. We have also observed a considerable reduction (10–15%) of thermal conductivity in our Al2O3-filled cured epoxy samples. We attribute this reduction to the increasing of thermal interfacial resistance between Al2O3 particles and cured epoxy matrix, induced by cure shrinkage during the reaction. Our experiments have demonstrated that systems with multiscale particle sizes exhibit lower viscosity and can be filled with much higher fraction of fillers. We thus expect that higher thermal conductivity (probably >12 W m−1 K−1 based on DEM) can be achieved in future via filling higher thermal conductivity spherical fillers (e.g., AlN, SiC), increasing loading fraction by multiscale-disperse packing and reducing the effect from cure shrinkage.

scholarly journals A Lattice Model for Elastic Particulate Composites

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1584 ◽  
Author(s):  
Darius Zabulionis ◽  
Vytautas Rimša
Keyword(s):  
Mechanical Response ◽  
Volume Fraction ◽  
Three Dimensional ◽  
Particulate Composite ◽  
High Volume ◽  
Spherical Particles ◽  
Particulate Composites ◽  
The Finite Element Method ◽  
Network Method

In the present article, a version of the lattice or spring network method is proposed to model the mechanical response of elastic particulate composites with a high volume fraction of spherical particles and with a much weaker matrix compared to the stiffness of the particles. The main subject of the article is the determination of the axial stiffnesses of the springs of the cell. A comparison of the mechanical response of a three-dimensional particulate composite cube obtained using the finite element method and the proposed methodology showed that the efficiency of the proposed methodology increases with an increasing volume fraction of the particles.

scholarly journals Analysis of Tortuosity in Compacts of Ternary Mixtures of Spherical Particles

Materials ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 4487
Author(s):  
Assem Zharbossyn ◽  
Zhazira Berkinova ◽  
Aidana Boribayeva ◽  
Assiya Yermukhambetova ◽  
Boris Golman
Keyword(s):  
Volume Fraction ◽  
Voronoi Tessellation ◽  
Porous Electrode ◽  
High Volume ◽  
Voronoi Cell ◽  
Porous Electrodes ◽  
Ternary Mixtures ◽  
Spherical Particles ◽  
Cell Parameters ◽  
Diffusion Properties

Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical Voronoi tessellation. For this purpose, a series of particle compacts geometrically similar to the actual porous electrode were generated using discrete element method; the radical Voronoi tessellation was constructed for each compact to characterize the structural properties; the tortuosity of compact porous structure was simulated by applying the Dijkstra’s shortest path algorithm on radical Voronoi tessellation. Finally, the relationships were established between the tortuosity and the composition of the ternary particle mixture, and between the tortuosity and the radical Voronoi cell parameters. The following correlations between tortuosity values and radical Voronoi cell parameters were found: larger faces and longer edges of radical Voronoi cell leads to the increased fraction of larger values of tortuosity in the distribution, while smaller faces and shorter edges of radical Voronoi cell contribute to the increased fraction of smaller tortuosity values, being the tortuosity values more uniform with narrower distribution. Thus, the compacts with enhanced diffusion properties are expected to be obtained by packing particle mixtures with high volume fraction of small and medium particles. These results will help to design the well-packed particle compacts having improved diffusion properties for various applications including porous electrodes.

Morphology, Distribution and Identification of Micro-Constituents Along Grain Boundaries in Nickel-Base Alloys

1973 ◽  
Vol 31 ◽  
pp. 176-177
Author(s):  
D. E. Fornwalt ◽  
A. R. Geary ◽  
B. H. Kear
Keyword(s):  
Electron Microscope ◽  
Grain Boundaries ◽  
Volume Fraction ◽  
Rupture Life ◽  
Stress Rupture ◽  
High Volume ◽  
Precipitate Morphology ◽  
Stress Rupture Life ◽  
Nickel Base ◽  
Scanning Electron

A systematic study has been made of the effects of various heat treatments on the microstructures of several experimental high volume fraction γ’ precipitation hardened nickel-base alloys, after doping with ∼2 w/o Hf so as to improve the stress rupture life and ductility. The most significant microstructural chan§e brought about by prolonged aging at temperatures in the range 1600°-1900°F was the decoration of grain boundaries with precipitate particles.Precipitation along the grain boundaries was first detected by optical microscopy, but it was necessary to use the scanning electron microscope to reveal the details of the precipitate morphology. Figure 1(a) shows the grain boundary precipitates in relief, after partial dissolution of the surrounding γ + γ’ matrix.

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