Shape Factor Distribution Research Articles

Bioinspired transparent ultratough birefringent photonic films with engineerable interference colors derived from in-situ synthesis of CaCO3

Chameleons can rapidly modify their coloration by manipulating the arrangement of iridophores encompassing guanine crystals in their dermis, which enables incident light to undergo birefringence. Various biomaterials have been designed to mimic the arrangement of guanine crystals, yet instances of synthesizing bottom-up structures with anisotropy for optical functionality remain rare. In this study, we report a novel two-step gas diffusion method for in-situ synthesis of CaCO3 (Vaterite) within a hydrogel to fabricate a bio-photonic film displaying birefringence interference colors. This strategy enables the successful fabrication of an inorganic–organic photonic film with superior mechanical properties and flexibility, resulting in high transparency, superior toughness, and adjustable optical anisotropy. Through a combination of experiment and simulation results, we elucidated the critical role played by shape factor (distribution) and structural factor (particle size) in producing transmitted interference colors. Finally, the birefringent photonic films prepared using the dot-plate method can function as optical patterns accurately representing the “on”/“off” state within a binary system. This system offers high spatial resolution, excellent repeatability, and precise controllability of optical properties, making it applicable in fields such as information encryption and decrytion. Our study has successfully synthesized photonic material with anisotropic structure though in-situ method while elucidating the underlying mechanism governing their ability to generate transmission interference colors, thus opening up new avenues for transparent flexible polarized optics, imperceptible wearable devices, and advanced information encryption.

Super-resolution of digital rock images with hybrid attention multi-branch neural network

High-resolution digital rock images are vital in studying microstructure and fluid flow characterization of oil and gas reservoirs. Computed tomography (CT) is currently the primary tool to acquire digital rock images because of its non-destructiveness and three-dimensional imaging capability. However, the restriction of imaging capability of CT sets a compromise between image resolution and field of view (FOV). The Hybrid Attention Multi-branch Super-Resolution Network (HAMSR) proposed in this study aims to remedy this deficiency. HAMSR employs a limited discrete distribution to capture all possible high-order information and generate reliable high-resolution images. The network is built to prioritize the recovery of pores, cracks, and textures in digital rock images by introducing channel and spatial attention mechanisms. The structure together with modules of HAMSR have been designed and optimized to yield superior performance with fewer parameters and less training time. HAMSR and several contemporary advanced models are trained on the DeepRock-SR 2D dataset which contains lots of sandstone and carbonate images. It is evident that HAMSR-generated images have minimal noise, clearer edges, and more micropores. Quantitative calculations show that compared to traditional bicubic interpolation, HAMSR acquires a 2.669 dB and 1.376 dB increase in peak signal-to-noise ratio (PSNR) respectively on the test sets (27%–38% reduction in relative error). Furthermore, the high-resolution (HR) images reconstructed by HAMSR are generally consistent with real HR images concerning statistical characteristics such as porosity, pore size distribution, shape factor distribution, and two-point correlation function. This work provides a new super-resolution model to generate high-quality digital rock images for further analysis.

Microstructure Design of Semi-Solid Slurry for Metal Direct Writing

Metal direct writing in semi-solid slurry is an innovative technology to realize low-cost printing of load-bearing parts in contrast to laser-based additive manufacturing. However, it is challenging to achieve near net-forming of 3D parts in the current stage because of the out of controlled microstructure and hence the unstable macro extrusion of the used semi-solid slurry. Here, mixed powder remelting (MPR) is introduced to actively design the characteristics of solid phases, i.e., solid fraction, shape factor, and size distribution. Specifically, high-melting-point pure Al powder served as the dispersed solid phases in the liquid phase that transformed from Al-Si alloy powder after remelting, leading to hypoeutectic Al-Si semi-solid slurry. The effectiveness of this approach was experimentally examined and kinetically modelled, to prepare semi-solid slurry with pre-set microstructure. The improved extrusion stability of semi-solid slurry can be anticipated, and it is universal for manufacturing of metal matrix composites slurry.

Three dimensional reconstruction of frost structure by replica method

To predict and control frosting phenomenon, three-dimensional structure of frost should be quantified in different environmental conditions. This paper experimentally studied frost structure using replica fabrication method. Supplying Formvar solution by a syringe pump under dry air, a plastic shell was successfully fabricated on the frost surface. The voids on the plastic shell were filled with a light-curing resin, from which a replica of frost was obtained. The three dimensional structures frost under different environmental conditions were reconstructed by μX-ray CT. The effects of environmental conditions on the local frost crystal shape, density and tortuosity factor distributions were quantitatively investigated. Frost shape was largely affected by the air relative humidity and temperature. A sheath-like crystal was observed at cooling plate temperature of -15 °C, while dendrite crystal formed at -25 °C. These results are consistent with the knowledge of snow crystal morphologies. The frost density and pore tortuosity factor increased with air velocity and relative humidity.

Comparative Study of Two Dimensional Boundary Layer over NACA 23012 and NACA 23021 Airfoils by Using Keller’s Box Method

This paper begins with general description onvarious methods for solving boundary layer equation. In particular, Prandtl's boundary layer equation is a simplified version of Navier-Stokes equation thatis solved integrally. Order of magnitudeanalysiscan be used to solve laminar and turbulent flow problems along the boundary layer.A more complex technique based onKeller’sbox method isalso discussed.This study aims atutilising a developed computercode which allows one to predict the development of boundary layer characteristics along airfoils’ surface, andhavea comparative understanding on flow behavioursbetween NACA 23012 and NACA 23021 airfoils, as well as 0⁰ and 5⁰angles of attack. The ability of Keller’s box method to solve the boundary layer equation prevails through correctskin friction,momentum thickness, and shape factor distributions over the surfaces. It was found that skin frictionin boundary layer over NACA23021 is higher than that over NACA23012 for about 10% of the chord length from the leading edge. However, momentum thickness of the boundary layer over NACA23021is lessthan the boundary layer momentum thickness over NACA23012for the whole chord length. Similarly, the shape factor Hfor the boundary layer over the formeris smallerin comparison to the latterfor about 30% of the chord length.

Development and validation of an analytical method for tensile strength determination of fibrous bulk solids

The increasing significance of products consisting of elongated particles or fibres along with a lack of understanding flow properties of fibrous bulk solids in processes urge for appropriate test procedures.Therefore, a tensile tester was designed with respect to the special needs in terms of test techniques of those bulk solids. The procedure of tensile strength determination was tested with regard to several possible influencing factors. Following from that, the manner of filling and filling height were identified to have the greatest influence on results. Furthermore, it is shown that the developed load system is capable of improving the repeatability of test results for fibrous bulk solids.Based on the derived standard procedure, systematic tests were carried out on beech and spruce chips in three different fractions each as well as model materials such as polypropylene fibres and differently sized bunches of glass fibres. The biomass materials have been characterised by dynamic image analysis prior to and after experiments resulting in particle size and shape factor distributions. It is found that tensile strength is affected by particle shape, size, roughness and interparticle contact area.

Fluidization behavior of graphitized glassy particles in a fluidized carbon bed cooling process for investment casting

Fluidized Carbon Bed Cooling (FCBC) is an innovative investment casting process for directional solidification of superalloy components. It takes advantage of a fluidized bed with a base of small glassy carbon beads for cooling and other low-density particles that form an insulating layer by floating to the bed surface. This so-called “Dynamic Baffle” protects the fluidized bed from the direct heat input from the high-temperature heating zone and provides the basis for an improved bed microstructure. The prerequisites for a stable casting process are stable fluidization conditions where neither collapse of the bed nor particle blow out at excessive bubble formation occur.This work aimed to investigate the fluidization behavior of spherical carbon bed material in argon and air at temperatures between 20 to 350 °C. Systematic studies at reduced pressures using the FCBC prototype device were performed to understand the stable fluidization conditions at all stages of the investment casting process. The particle shape factor and size distribution characterization and the measurement of the powder’s minimum fluidization velocity and bed voidage show that this material can be fully utilized as a cooling and buoyancy medium during the FCBC process.

A mixing formula accounting for inversion of matrix structure

Known mixing models are analyzed with the aim to retrieve permeability of metal inclusions from the measured constitutive parameters of a binary composite. The application-oriented models are interpreted in terms of inclusion shape-factor and percolation threshold, which are two measurement-fitted parameters. A model that accounts for the inversion of the Maxwell Garnett matrix structure is proposed. The structure inversion point is close to the percolation threshold, and the inversion takes place within a transition filling range that is a third fitting parameter. The proposed model is compared with the effective medium model in terms of the complex susceptibility calculated as the function of filling and of frequency and in terms of Bergman-Milton shape-factor distribution charts. The model validity is illustrated by treatment of the measured microwave constitutive parameters of a composite filled with carbonyl nickel.

Permeability Model for Porous Transducer With Glass Spheres Packing

A theoretical model is developed for predicting permeability of a porous transducer, which is a crucial component of liquid circular angular accelerometer and sintered by glass microspheres. The proposed permeability model of the transducer is determined with consideration of its shape factor, tortuosity, and particle size distribution (PSD) characterized by equivalent mean diameter and skewness. A novel analytical method for calculating the shape factor for the arbitrary cross-section area is derived. In addition, a tortuosity model is designed by fitting skewness and tortuosity of particle packing beds in a regular tetrahedron microspheres arrangement structure. Together with the analytical model of shape factor, the tortuosity fitting model and a method to determine equivalent diameter from PSD, the permeability model is implemented to compare with Kozeny–Carman (KC) model. The experiments are performed to measure the permeability of four types of porous transducers fabricated with different PSDs and consequently validate the permeability model. The results indicate that the proposed model can be utilized for predicting permeability of porous transducer with higher precision.

Symmetric/asymmetric separation transition in a supersonic combustor with single-side expansion

Shock wave induced separation in a canonical supersonic combustor is studied through numerical simulation and experiment. Cold flow analysis is implemented to obtain the dynamic features of the symmetric/asymmetric separation transition process. Experiments have been carried out in a single-expanding duct with backpressure produced by a cylinder at Mach number 3. Detached-eddy simulation represents the whole process of the separated region development. Typical simulated transient flow phases are validated by the nano-based planar laser scattering images. The results of the computational study show reasonable agreement with experiments, although the movement of simulated separation shock is slightly faster. It is found that a complex transitional separation occurs when the backpressure is near the threshold. During the dynamic process, the symmetric/asymmetric separation transition is bidirectional. A mechanism for the separation transition is identified based on boundary layer analysis. Results show that the key factor of the separation transition is the velocity/momentum profile fullness (shape factor) distribution of the boundary layers from both walls. An interlaced shape factor distribution means that the separation tendency of two turbulent boundary layers exchanges, which accounts for the switch of separation modes. A lag exists between the boundary layer transformation and the separation transition. A large amplitude, broadband low-frequency shock oscillation exists in the transitional flowfield, which has a relationship with low-frequency unsteadiness in traditional shockwave boundary-layer interaction problems. Future effort is required in discovering the mechanism of low-frequency unsteadiness in complex separation cases.

Multi-porosity multi-physics compositional simulation for gas storage and transport in highly heterogeneous shales

Shale gas reservoir is comprised of highly heterogeneous porosity systems including hydraulic/secondary fractures, inorganic and organic matrix. Multiple non-Darcy flow mechanisms in the shale matrix further bring challenges for modeling. In this paper, we developed a framework combining a multi-physics compositional simulator with Multi-Porosity Modeling preprocessor for gas storage and transport in shale. A Triple-Porosity Model is used to characterize the three porosity systems in shale gas reservoirs. In the fracture porosity the heterogeneous impact of secondary fractures distribution on matrix-to-fracture fluid transfer is revealed by shape factor distribution. They are upscaled with superior accuracy from a detailed Discrete Fracture Network Model (DFN) sector model, where orthogonal hydraulic fractures are explicitly discretized. With the occurrence of nano-pores in shale matrix, the interaction between pore-wall and gas molecules is considered via Knudsen diffusion and gas slippage. Gas adsorption on the pore-wall of organic matrix is modeled by extended Langmuir isotherm. The inter-porosity and intra-porosity connectivities in the Triple-Porosity Model are flexibly controlled by arbitrary connections. Our results show that gas production in the Triple-Porosity Model with shape factor upscaled from DFN exhibits different production performance from models with uniform shape factor distribution. The deviations are caused by the dominance of different regions at different production periods. Connection topology in the shale gas reservoir is also comprehensively assessed. We demonstrate that the intra-porosity connections in the inorganic and organic matrix have negligible impact on the global gas flux, while the inter-porosity connections have different levels of importance for the gas production. Moreover, different combinations of flow and storage mechanisms are investigated. We show that Langmuir desorption maintains reservoir pressure, but gas slippage and Knudsen diffusion accelerate the pressure drop. Both mechanisms contribute to improve the gas production and the consideration of them simultaneously improve gas production most.

Influence of particle size and shape properties on cake resistance and compressibility during pressure filtration

The aim of this paper was to study cake filterability and compressibility as a function of the particle shape and particle size distribution (PSD). Different shapes and PSD of calcium carbonate and uranium oxalate particles covering the classical types encountered in industry (sphere, cube, needle and platelet) were obtained by precipitation. The size and shape factor distributions were measured using an image analysis system on SEM pictures. The cake filtration properties were measured in ideal monitored operating conditions, because of a miniaturised filtration cell set-up. The impact of the PSD and the shape were quantitatively assessed. These two solid features have an impact on cake resistance and compressibility, but not in the same way. The PSD has the strongest effect on cake resistance and compressibility. The particle shape is a decisive parameter for cake compressibility when the shape is far from the sphere. Both parameters need to be considered when working on the development of a filtration operation. Here, a practical model built following the Darcy law coupled with a new correlation for compressibility factor assessment is proposed. It gave satisfactory estimates of cake filterability and compressibility for the four shapes studied.

A typology of street patterns.

We propose a quantitative method to classify cities according to their street pattern. We use the conditional probability distribution of shape factor of blocks with a given area and define what could constitute the 'fingerprint' of a city. Using a simple hierarchical clustering method, these fingerprints can then serve as a basis for a typology of cities. We apply this method to a set of 131 cities in the world, and at an intermediate level of the dendrogram, we observe four large families of cities characterized by different abundances of blocks of a certain area and shape. At a lower level of the classification, we find that most European cities and American cities in our sample fall in their own sub-category, highlighting quantitatively the differences between the typical layouts of cities in both regions. We also show with the example of New York and its different boroughs, that the fingerprint of a city can be seen as the sum of the ones characterizing the different neighbourhoods inside a city. This method provides a quantitative comparison of urban street patterns, which could be helpful for a better understanding of the causes and mechanisms behind their distinct shapes.

On the Axisymmetric Turbulent Boundary Layer Growth Along Long Thin Circular Cylinders

Even after several decades of experimental and numerical testing, our present-day knowledge of the axisymmetric turbulent boundary layer (TBL) along long thin circular cylinders still lacks a clear picture of many fundamental characteristics. The main issues causing this reside in the experimental testing complexities and the numerical simplifications. An important characteristic that is crucial for routine scaling is the boundary layer length scales, but the downstream growth of these scales (boundary layer, displacement, and momentum thicknesses) is largely unknown from the leading to trailing edges. Herein, we combine pertinent datasets with many complementary numerical computations (large-eddy simulations) to address this shortfall. We are particularly interested in expressing the length scales in terms of the radius-based and axial-based Reynolds numbers (Rea and Rex). Although the composite dataset gave an averaged shape factor H = 1.09 that is substantially lower than the planar value (H = 1.27), the shape factor distribution along the cylinder axis actually begins at the flat plate value then decays logarithmically to near unity. The integral length scales displayed power-law evolutions with variable exponents until high Rea (Rea > 35,000) where both scales then mimic streamwise consistency. Beneath this threshold, their streamwise growth is much slower than the flat plate (especially at low-Rea). The boundary layer thickness grew according to an empirical expression that is dependent on both Rea and Rex where its streamwise growth can far exceed the planar turbulent flow. These unique characteristics rank the thin cylinder axisymmetric TBL as a separate canonical flow, which was well documented by the previous investigations.

Analysis of the size and shape of polydisperse dust particles in a complex glow discharge plasma

The size and shape factor distribution of levitating particles is studied by the method of extraction of dust particles from the discharge chamber. Two dust traps existing in a glow discharge in the strata and above the lower wall of the tube near the bend in the current channel are investigated separately. It is found that the size distribution of polydisperse particles of an arbitrary shape is of the bimodal type due to simultaneous levitation of particles with two shape factors. Polydisperse spherical particles of any size exhibit levitation due to the separation of particles over the wall thickness. For identical parameters of the discharge, the size of the particle in neon is slightly larger than in krypton; the particle size in the trap located in a stratum is substantially larger than the particle size in the trap above the wall of the discharge tube. Precision determination of the shape and size of particles makes it possible to estimate the electric field strength for dust traps. It is shown that the glow discharge can be used as a tool for separation of dust particles in a wide range of their sizes.

An Inverse Design Method for Cascades for Low-Reynolds Number Flow

Inverse design of cascades for low Reynolds number can be applied for the aerodynamic development of fans and compressors. The present contribution describes a complete design procedure by taking into account the transition from laminar to turbulent boundary layer flow. A shape factor distribution is prescribed along the suction surface of the blades. The inverse boundary layer calculation is performed by the application of a finite difference method. On the pressure side the velocity distribution is prescribed in such a way that the given flow angles in front of and behind the cascade are realized. An inverse calculation based on potential theory is applied in order to determine the geometry of the cascade. At the end of the present contribution a cascade is designed by the described inverse design procedure and the flow is simulated by the application of CFD.

Development of New Powdered Additive and Its Application for Improving the Paperboard Bulk and Reducing Drying Energy (I)-Analysis of Chemical and Physical Properties of Brewers Grain -

Brewers grain is a byproduct of beer brewing and consists primarily of grain husks, pericarp, and fragments of endosperm. Although this material is consumed by animals and used as fertilizer, a large amount of brewers grain is simply discarded. Therefore, new methods for utilizing this fibrous resource should be pursued. In this study, we examined the potential utilization of brewers grain as an additive in the paperboard industry by determining the chemical composition of brewers grain and the physical properties of brewers grain powders after grinding with two types of grinders. We found that brewers grain had a lower holocellulose content and higher lignin content and intermediate ash content when compared to other biomass materials, and did not contain any contaminants that would interfere with the papermaking process. Particles had a higher fiber length, less fiber width, and narrower shape factor distribution when ground by a blender type grinder than by a pin crusher type grinder. The blender type grinder was concluded to make regular brewers grain particles appropriate for papermaking.

Growth simulation for 3D surface and through-thickness cracks using SGBEM-FEM alternating method

An SGBEM-FEM alternating method had been proposed by Nikishkov, Park and Atluri for the analysis of three-dimensional planar and non-planar cracks and their growth. The proposed method is an effective method for fatigue or stress corrosion crack growth simula- tion. During crack growth simulation, however, an oscillation phenomenon is observed in crack advance or stress intensity factor distri- bution. If oscillating amplitude in SIF or crack advance does not decrease during next increment steps, the crack growth simulation fails. In this paper several methods are examined to remove the oscillation phenomenon. As a result, it is found that smoothing in stress inten- sity factor distribution or in crack front geometry can remove or weaken the oscillation phenomenon. Using the smoothing techniques, stress corrosion crack growth simulation is performed for a semi-elliptical surface crack and a through-thickness crack embedded in a plate. Crack front shape and stress intensity factor distribution are obtained after each increment during the crack growth. And the depth and length of a crack are obtained as a function of time. It is noted that the SGBEM-FEM alternating method is a very effective method for SCC growth simulation for a surface crack and a through-thickness crack.

Network model investigation of interfacial area, capillary pressure and saturation relationships in granular porous media

We have developed a new approach for generating pore throat cross sections of various shapes based on distributions of shape factors and radii of inscribed circles. These distributions are obtained from analysis of grains packing. General formulas for calculating geometrical properties and entry capillary pressure for given shape factor and inscribed circle radius are developed. These relationships are employed in a pore network, which has a number of special features. In particular, it is highly flexible in terms of location of pore bodies, variable coordination number, as well as variable cross‐sectional shapes. The pore network model is employed for simulating the equilibrium distribution of two fluids in a granular porous medium, under both drainage and imbibition conditions. The pore network model is verified by comparing simulation results with experimental data of quasi‐static drainage and imbibition experiments in a glass bead medium. The pore‐level topology and geometrical description of pore bodies and pore throats, essential for building the network, are rigorously extracted from experimental data using image analysis (3DMA‐Rock software). Calculated capillary pressure‐saturation (Pc − Sw) and specific interfacial area‐saturation (anw − Sw) curves show very good agreement with measured ones, for both drainage and imbibition. We show that the shape factor can significantly influence the form of macroscopic Pc − Sw and anw − Sw curves, if the length and volumes associated to the pore throats are considerable. Furthermore, using continuous generation of shape factor distribution, the model can be validated against the grain size distribution. After validating the model against experiments, in addition to primary and main curves, we simulate many scanning curves to generate Pc − Sw − anw surfaces for drainage and imbibition, separately. Results show that these two surfaces lie very close to each other, and the average normalized difference is small, in the range of simulations uncertainty. Our results illustrate that Pc − Sw − anw surfaces show very little hysteresis and, therefore, specific interfacial area can be considered as an essential variable for reducing or eliminating the hysteresis observed in Pc − Sw curves.

Water-Insoluble Particles in Spring Snow at Mt. Tateyama, Japan: Characteristics of the Shape Factors and Size Distribution in Relation with Their Origin and Transportation

The number-size distribution and shape factors of water-insoluble particles (WIP) in four dirty snow layers in the spring of 2001 at Mt. Tateyama, Japan, were analyzed using scanning electron microscopy, and using optical microscopy with a digital camera. Results show that the median aspect ratio (ratio of the longest dimension b to the orthogonal width a; b/a) of the WIP varied within 1.22-1.31. Only a few particles with an aspect ratio of more than 2.5 were observed. The median circularity factor (4πS/l 2 ; S is projection area, and I is periphery length) varied from 0.83-0.97. Combined with backward air trajectories, visibility reducing surface weather reports, additional results of rain containing Saharan dust and dry deposition samples, the number and shape factor distributions versus particle size were characterized as (1) narrower distributions of number-size and shape factors for the Saharan dust, and (2) bi-modal number-size distribution for dry deposited dust. Results suggest that the proportions of nearly spherical (higher circularity nearly 1) and less elongated (lower aspect ratio close to 1) particles were higher in the sample that had been transported a longer distance from the dust source areas.