non-spherical particles

Top PDF non-spherical particles:

Artifcial neural network approach for the prediction of terminal falling velocity of non-spherical particles through Newtonian and non-Newtonian fluids

Artifcial neural network approach for the prediction of terminal falling velocity of non-spherical particles through Newtonian and non-Newtonian fluids

The investigation of the terminal falling velocity of non-spherical particles is currently one of the most promising topics in sedimentation technology due to its great significance in many separation processes. In this study, the potential of Artificial Neural Networks (ANNs) for the prediction of non- spherical particles terminal falling velocity through Newtonian and non- Newtonian (power law) liquids was investigated using 361 experimental data. ANNs emerged as the most popular non-linear mathematical models due to their good prediction, simplicity, flexibility and the large capacity which moderate engineering endeavor, and the availability of a large number of training algorithms. The developed ANN model demonstrated the acceptable values for the prediction of terminal falling velocities such as the determination coefficient ( R2), MSE, and MRE which were equal to 0.9729, 0.0023, and 21%, respectively. In an investigation on terminal falling velocity and drag coefficient of spherical and non-spherical particles, it was found that the terminal falling velocity of non-spherical particles to spherical particles was 0.1.
Show more

14 Read more

Numerical determination of the effective moments of non spherical particles

Numerical determination of the effective moments of non spherical particles

As stated above, for a spherical particle in a uniform field, there is a dipole moment and all higher order moments are zero. The standard assumption in DEP or impedance spectro- scopic measurement of particle suspensions assumes that the particle is spherical and all higher order moments are zero. Non-spherical particles can have significant higher order com- ponents, and in some cases these moments strongly influence the observable motions. The presence of higher order contri- butions to the energy stored in the field would lead to errors in estimating the dipole moment of the particle. This prob- lem becomes important when the electric field is highly non- uniform or at high volume fractions, as the field from higher order moments decreases much more rapidly than the dipole. The force and torque in non-uniform electric fields are affected directly by these higher order moments for non- spherical particles. The first two terms in the dielectrophoretic (DEP) force F DEP and electrorotational torque Γ ROT are [5]
Show more

8 Read more

Modelling of Non-Spherical Particles in Dilute Non-Colloidal Suspensions Using SPH

Modelling of Non-Spherical Particles in Dilute Non-Colloidal Suspensions Using SPH

Abstract: Suspensions and their applications can be found in many engineering, environmental or medical fields. Considering the special field of dilute suspensions, possible applications are cement paste or procedural processes in the production of medication or food. While the homogenized behavior of these applications is well understood, contributions in the field of pore-scale fully resolved numerical simulations with non-spherical particles are rare. Using Smoothed Particle Hydrodynamics as a simulation framework we therefore present a model for Direct Numerical Simulations of single-phase fluid containing non-spherically formed solid aggregates. Notable and discussed model specifications are the surface-coupled fluid-solid interaction forces as well as the contact forces between solid aggregates. Moreover we simulate and analyze the behavior of dilute non-colloidal suspensions of non-spherical solid particles in Newtonian fluids. The focus of this contribution is the numerical model for suspensions and its implementation in SPH. Therefore shown numerical examples present application examples for a first numerical analysis of influence factors in suspension flow. Results show that direct numerical simulations reproduce known phenomena like shear induced migration very well. Moreover the present investigation exemplifies the influence of concentration and form of particles on the flow processes in greater detail.
Show more

12 Read more

A new contact detection algorithm for three dimensional non spherical particles

A new contact detection algorithm for three dimensional non spherical particles

A new algorithm for contact detection between convex polygonal and polyhedral particles in the discrete element method, Computers and Geotechnics, 44 2012 73-82.. Kuipers, Quaternions an[r]

27 Read more

Discrete Modelling of Compaction of Non-spherical Particles

Discrete Modelling of Compaction of Non-spherical Particles

The macroscopic property of a compact is a collective outcome of the microscopic interactions between particles. For this purpose, the discrete element method (DEM) offers an efficient way to obtain micro- mechanical insight into its behaviour as it treats particles individually and explicitly considers the particle characteristics, material properties and the inter-particle forces. DEM has been adopted to investigate particle compaction, such as the effect of mechanical properties of particles [2, 3], particle-wall friction induced inhomogeneity [4], evolution of compact structure [5] and the effects of moisture, particle shape and particle size [6-8]. Recently we conducted a DEM study of the compressive strength of iron ore compacts using a bonded particle model [16]. The simulated stress-strain responses were comparable with those observed from the physical experiments.
Show more

6 Read more

Estimation of particle size distribution and aspect ratio of non-spherical particles from chord length distribution

Estimation of particle size distribution and aspect ratio of non-spherical particles from chord length distribution

We applied the algorithm to previously collected CLD data for slurries of needle shaped crystalline particles of COA with different particle size distri- butions. COA slurries were characterised using FBRM (to measure CLD), imaging (to measure EQPC, maximum and minimum Feret diameters) and laser diffraction (to measure PSD based on equivalent sphere diameter ap- proximation). Measured CLD data were used in the algorithm without any further information input, using two different CLD geometrical models, one for ellipsoids and the other one for thin cylinders. Best estimates for particle aspect ratios and corresponding PSDs were obtained with each model and these were compared to experimental data from imaging and laser diffraction. Estimated aspect ratios from the thin cylinder model were in good agree- ment with those obtained from the ratio of maximum and minimum Feret diameters, while those from the ellipsoid model were somewhat higher. Cor- responding to this, there was a good agreement between measured and fitted CLDs for the thin cylinder model, but some discrepancies could be seen for the ellipsoid model. Ranges and modes of particle size distributions deter- mined for both models were in a good agreement with those obtained by imaging. Although it was possible to estimate aspect ratios of needle like particles from CLD data reasonably accurately for the system analysed here, the optimisation problem of finding most appropriate PSD and aspect ra- tio would be greatly simplified if additional information about particle size range or shape is available, for example from a suitable imaging or scattering technique, especially in the case of systems with significant polydispersity or multimodality in terms of particle shape or size.
Show more

53 Read more

Dynamics of single, non-spherical ellipsoidal particles in a turbulent channel flow

Dynamics of single, non-spherical ellipsoidal particles in a turbulent channel flow

The aim of the present work was to study the effect of particle shape, inertia, initial orientation and position within the boundary layer in a turbulent channel flow on the translational and orientational behaviour of single non-spherical particles, assuming one- way coupling between the fluid and the particles. Most of the reported research efforts in this area, i.e. on single particle dynamics, have focused on analytical solutions in frozen flow fields, and in many cases, only prolate spheroids have been considered. However, the characteristic translational and rotational dynamics of non-spherical particles resulting from their interactions with the turbulent environment has not been fully elucidated. This study considers a number of particle aspect ratios, with   1 for oblate spheroids,   1 for spheres, and   1 for prolate spheroidal particles, which complements other studies available in the literatures. Another important aspect of the present work is that the particle size is based on the equivalent volume diameter, where particles with the same relaxation time have equal mass, volume and density. Hence, any difference in the behaviour amongst particles with the same relaxation time will be as a result of the difference in shape and orientation alone. The fluid phase is described as a continuum in an Eulerian framework, with the time-dependent flow and turbulence predicted using large eddy simulation, with the sub-grid scale motions modelled using a dynamic approach. The motion of non- spherical particles is computed in a Lagrangian framework using a point-wise approximation (which means that for the largest needle-like particles results are likely to be qualitatively rather than quantitatively accurate). The particle’s non-sphericity is modelled by coupling Lagrangian particle tracking with the Euler equation of rotational motion in the particle frame. The study is based on the approach of Yin et al. (2003) and extends earlier work (Njobuenwu and Fairweather, 2013a, b, 2014) by accounting for fluid rotation in a dynamic system when computing the torque due to the resistance to relative rotation of a rigid non-spherical particle.
Show more

46 Read more

Effect of shape on inertial particle dynamics in a channel flow

Effect of shape on inertial particle dynamics in a channel flow

Particle dynamics in a channel flow are investigated using large eddy simulation and a Lagrangian particle tracking technique. Following validation of single-phase flow predictions against DNS results, fluid velocities are subsequently used to study the behaviour of particles of differing shape assuming one-way coupling between the fluid and the particles. The influence of shape- and orientation-dependent drag and lift forces on both the translational and rotational motion of the particles is accounted for to ensure accurate representation of the flow dynamics of non-spherical particles. The size of the particles studied was obtained based on an equivalent-volume sphere, and differing shapes were modelled using super-quadratic ellipsoid forms by varying their aspect ratio, with their orientation predicted using the incidence angle between the particle relative velocity and the particle principal axis. Results are presented for spherical, needle- and platelet-like particles at a number of different boundary layer locations along the wall-normal direction within the channel. The time evolution and probability density function of selected particle translational and rotational properties show a clear distinction between the behaviour of the various particles types, and indicate the significance of particle shape when modelling many practically relevant flows.
Show more

22 Read more

THEORETICAL INVESTIGATION OF WALL EFFECT ON DRAG COEFFICIENT OF DIFFERENT PARTICLES SHAPE MOVING IN NON-NEWTONIAN FLUIDS

THEORETICAL INVESTIGATION OF WALL EFFECT ON DRAG COEFFICIENT OF DIFFERENT PARTICLES SHAPE MOVING IN NON-NEWTONIAN FLUIDS

The problem of describing the settling velocity of a falling spherical and non-spherical particle in non-Newtonian fluid is important in many application ,In unit operation such as centrifugal and gravity collection and separation also viscosity measurements in non-Newtonian fluid using the falling ball method.It is also necessary to know the time distance required to reach the terminal velocity, Clift et al(1978) .In this state of non-spherical particles less information founded in the literature survey when the particle settling in the fluid subjected to different force gravitational force (FG),drag force (FD),and buoyancy force (FB) ,this force when reach to equilibrium happen the terminal velocity,Brown Phillip.P(2003).When the particle start moving in the fluid ,a velocity dependent on drag force start subjected on it.This velocity dependent on drag coefficient of the particle ,it is defined by;
Show more

22 Read more

An Analytical Approach for Determination of Riverbank Erosion under Action of Capillary Cohesion, Viscous Force and Force due to Pore Pressure

An Analytical Approach for Determination of Riverbank Erosion under Action of Capillary Cohesion, Viscous Force and Force due to Pore Pressure

The Truncated Pyramid Model has been conceived based on the fact that a particle tends to be in a stable position and that each particle will lie on top of two particles with a small-volume water bridge between them. According to the model, each particle, spherical in shape and materially homogeneous, rests on two particles in the form of a truncated pyramid with a small volume water bridge between them. A small, gradual increase in the size of the particles is assumed as heavier and bulkier particles will be placed at the bottom and away from the river. The geometry of the arrangement of particles, their dimensions and parameters, like the inter-particle distance and volume of Water Bridge, will determine the geometry of the bank itself. Suffices i and j indicate the spatial location of a particle in two- dimensional frame. Here i is the row number and j is the column number. For example, particle 24 is the fourth particle in the second row and it rests on particles 34 and 35. Radius of a particle at a location ij is denoted as R ij . Radius of the
Show more

7 Read more

Particle engineering of materials for oral inhalation by dry powder inhalers  II   Sodium cromoglicate

Particle engineering of materials for oral inhalation by dry powder inhalers II Sodium cromoglicate

Initial attempts by Vidgrén et al. (1987) to use spray drying to produce particles of sodium cromoglicate suitable for inhalation therapy, by spray drying from a water/ethanol solution, produced almost spherical, partially shrunken particles. These researchers compared the physical properties and in vitro inhalation behaviour of the spray dried particles with mechanically micronised particles and reported the spray dried particles to be smaller, mainly in the range of 1-5 µm, with improved lung deposition as ascertained from impaction studies. Steckel et al., (2003) also prepared sodium cromoglicate in a respirable particle size, using an in situ micronisation controlled crystallisation technique and compared these particles to the commercial dry powder formulation, Intal ® . Delivery of these engineered particles via the Spinhaler ® device at a flow rate of 100 l/min resulted in a measured fine particle fraction of 45.5%, a statistically significant increase in the fine particle fraction compared to the commercial product (14.5%). The particles produced by both Vidgren et al. (1987) and Steckel et al. (2003) were spherical in shape and were non-porous.
Show more

48 Read more

Dynamic Numerical Investigation of Random Packing for Spherical and Nonconvex Particles

Dynamic Numerical Investigation of Random Packing for Spherical and Nonconvex Particles

In order to better understand these complex behaviours, numerous numerical algorithms have been developed. Their objective is to compute dense configurations and to study their properties. As expected, most of these algorithms have been developed to compute configurations for spherical particles. They can be divided into two classes we are going to call geometrical algorithms and dynamic algorithms. By geometrical algorithms we mean methods whose objective is to create dense configurations in order to study them, these configurations being obtained without any underlying physical behaviour of the particles. Some of these methods are beginning by generating randomly the centers of the spheres in a cubic lattice with periodic boundaries. It is the case in [14], where each point is the center of an inner and an outer sphere. The real sphere is the inner one and the algorithm iteratively eliminates overlappings while slowly reducing the outer diameter. The algorithm stops when inner and outer diameters coincide. This algorithm generates packings where only two spheres are actually in contact but lot of spheres are nearly touching. Configurations of 1, 000 monosized spheres with mean packing fraction close to 64% are studied. The number of neighbours (couples of spheres whose distance is lower than a fixed parameter η) converges to 6 when the contraction rate and the parameter η go to zero. In [16], randomly generated points are also used and the spheres are growing from these points at a fixed rate. The contacts occurring during the evolution of the particles are treated as elastic contacts. A configuration of 8, 000 monosized spheres is created with a mean packing fraction equal to 63.7% and a mean number of contacts equal to 5.83. Sequential algorithms can also be used to create packings: they consist in positioning spheres one after the other. This type of method has been used in [21] to create random loose packings of spheres in a cylindrical container (higher
Show more

20 Read more

Fine and coarse dust separation with polarization lidar

Fine and coarse dust separation with polarization lidar

As a consequence of the partly large uncertainties, we use both, the one-step and two-step methods, in a complemen- tary sense. As mentioned, the lower number of input pa- rameters leads to lower uncertainties in the results of the one-step method. The two-step method, on the other hand, provides more insight into the dust optical properties. We use the dust backscatter profiles obtained with the one-step method as a quality standard. The sum of the fine and coarse dust backscatter profiles obtained with the two-step approach should approximately match the one obtained with the one- step method. As mentioned above, we may also assume a fine-mode dust contribution of about 30 % to backscatter, extinction, and optical depth (as the AERONET observa- tions in Sect. 3 suggest) in the case of desert dust outbreaks. Then, we can roughly estimate the fine- and coarse-mode dust backscatter profiles from the total dust backscatter co- efficient (one-step method) and compare these profiles with the respective ones obtained with the two-step method. Large discrepancies may then indicate that some basic assumption in the two-step data analysis must be changed and improved. The backscatter profile for the non-dust component obtained
Show more

19 Read more

Synthesis and Characterization of Diesel, Kerosene and Candle Wax Soot’s

Synthesis and Characterization of Diesel, Kerosene and Candle Wax Soot’s

Diesel, kerosene and candle wax soot’s were characterized in this study with modern analytical equipment to determine the nature of soot particles. Soot particles were found to form aggregates which were spherical in their morphology. The Raman spectra obtained in this study provide information to confirm these soot’s to be double walled nanomaterial as observed from their D and G bands. The energy dispersive spectroscopic analyses (EDS) of these soot particles show the presence of silicon and sulphur in substantial quantity to enable their positive identification. The scanning electron microscopy and transmission electron microscopy analysis of these soot particles confirm our deduction of the soot particles as spherical nanomaterials made up of amorphous and spherically shaped carbon nanospheres with significant configuration to be identified as sp 2 hybridized double walled carbon nanotubes. The size of these soot particles in the nano-range make them dangerous when inhaled.
Show more

10 Read more

Anomalous oxidation of Fe Si alloys under a low oxygen pressure at 800 °C

Anomalous oxidation of Fe Si alloys under a low oxygen pressure at 800 °C

expels iron which later nucleates and grows to spherical particles and moves out. The other source is the base alloy: in this case the driving force for diffusion is the activity difference [1] and the compressive tension generated during oxidation [45]. Adachi et al. [1] proposed that iron is transported through the SiO 2 layer in the form of atoms rather than of ions.

29 Read more

Cassava Leaf Nanoparticles (CLNPs) as a Potential Additive to Anti-Corrosion Coatings for Oil and Gas Pipeline

Cassava Leaf Nanoparticles (CLNPs) as a Potential Additive to Anti-Corrosion Coatings for Oil and Gas Pipeline

Nanoparticles which have a wide range of applications in bio-medical, composites, solar cells and engineering applications are being processed through two (2) major approaches, namely; top-down method and bottom-up method [26-29]. Since, most agro-wastes are used for engineering applications; agro-waste can be processed into nanoparticles for various applications [26,27] Bello et al. [30] reported the synthesis of uncarbonised coconut shell nanoparticles. Coating is one of the most efficient methods used for combating corrosion in the oil and gas industry [31-33]. Coatings may be applied alone or may be used with other common methods such as proper material selection, cathode protection (CP) and application of inhibitors to modify the corrosive environment [34,35]. Anti – corrosion coatings generally operate mainly be three mechanisms namely; barrier creation between substrate materials and environments, inhibition of the corrosion processes, and coating acting as sacrificial materials. However, recently one of the newest approaches is what is called “active- passive”. Here the coating acts as a barrier layers which will not allow permeation of corrosive agents to the metal surface (passive). While the active approach allows the formation of effective passive layer and this will impedes the corrosion half reactions leading to Schottky barrier at the interface resulting in depletion of electrons [21]. Nanoparticles can be incorporated as additives in coatings to inhibit corrosion. Incorporating nanosize additives in coatings provide effective barrier performance, reduce the amount of holiday in coatings and also enhance the integrity and durability of coatings. Since the fine particles dispersed in coatings can fill cavities and extract from cassava leaf contains organic compound in them, these will further improve metallic coating properties.
Show more

10 Read more

The margination propensity of spherical particles for vascular targeting in the microcirculation

The margination propensity of spherical particles for vascular targeting in the microcirculation

interaction of leukocytes with RBCs which tend to push the former away from the center of the capillary towards the opposing wall [9], and it is no at all related to gravita- tional forces, as clearly demonstrated by [10]. Systemi- cally administered particles for the delivery of drugs and other therapeutic agents have a characteristic size at least one order of magnitude smaller than leukocytes and RBCs (O (10) μ m), and, more importantly, than the thickness of the cell free layer (O (10) μ m). As a consequence, the mar- gination of nanoparticles can not only rely on the interac- tion with other circulating cells, especially in the microcirculation where RBCs are less abundant. The mar- gination dynamics of nanoparticles has to be controlled by their size, their shape and their possible interaction with external long range force fields, as the gravitational and electromagnetic fields.
Show more

9 Read more

Effect of Orifice Introduction on the Pneumatic Separation of Spherical Particles

Effect of Orifice Introduction on the Pneumatic Separation of Spherical Particles

Particles of density 2500 kg·m ¹3 moved upward at lower speeds than those of density 1500 kg·m ¹3 . The upward velocity was increased by the larger high-velocity region as the number of orifices increased. Two orifices yielded the highest velocity. As the number of orifices increased further, the particles collided more frequently with the orifices. Consequently, the residence time was increased because particles striking certain parts of the orifices were reflected vertically downward. The column height was maintained constant in the simulations. However, the results indicated that a shorter column height with reduced orifice spacing would increase the upward velocity of light particles and decrease the frequency of orifice collisions. We will investigate the effect of column height in future studies.
Show more

8 Read more

Morphology and Magnetic Properties of Platelet γ Fe2O3 Particles

Morphology and Magnetic Properties of Platelet γ Fe2O3 Particles

ferromagnetic particles in magnetic hyperthermia or thermoablation. The platelet ¡ -FeOOH particles were prepared through the formation of a precipitant followed by the hydrothermal treatment of the precipitant. The shape of the ¡ -FeOOH particles changed from elongated to platelet- like depending on the quantity of ethanolamine in the precipitant. The size of the platelet ¡ -FeOOH particles was reduced from 90 ­ 120 to 40 ­ 60 nm as the precipitant temperature was lowered in the range from 5 to ¹ 3°C. The formation of dimples was observed during the dehydrating process from ¡ -FeOOH to ¡ -Fe 2 O 3 , and was con fi rmed from the increase in the BET surface area of the ¡ -Fe 2 O 3 particles. The particle size and
Show more

5 Read more

Gravitational sedimentation of cloud of solid spherical particles at small Reynolds numbers

Gravitational sedimentation of cloud of solid spherical particles at small Reynolds numbers

On the first stage the formation of spheroidal cloud occurs accompanied by circulation of peripheral particles in the opposite direction to cloud motion. The time of spheroid formation t depends on the initial mass and concentration of the particle cloud. For the present experiments this time was varied within t = (1 ÷ 4) s.

6 Read more

Show all 10000 documents...