Hollow Cylinder Research Articles

Experimental and numerical estimation of wall effect and drag coefficient on hollow frustum settling in annular and non-annular channels

The wall effect and drag coefficient of hollow frustum particles (Tapered hollow cylinders) settling in cylindrical non-annular and annular channels were experimentally investigated. The terminal velocity, V, of the hollow frustum particles is measured by considering flow channels of different diameters filled with various working fluids. The present work deals with the study of drag coefficient for a range of 0.12 ≤ deq/D ≤ 0.44, 0.22 ≤ deq/L ≤ 0.43, and 0.22 ≤ di/do ≤ 0.77. The hollow frustum particle's terminal velocity, V, decreases with increased blockage ratios and di/do ratios. The experiment revealed that the frustum attains a steady-state orientation. The hollow frustum particle is affected by the wall's retardation, which is described by the wall factor. The hollow frustum particle's wall factor (f) depends on the Reynolds number (Re) and blockage ratio. The wall factor increases with increasing Reynolds number up to a certain point called critical Reynolds number, Rec; after that, the wall factor remains constant with increasing Reynolds number. The hollow frustum particles settling in the cylindrical non-annular channel were more subjected to wall effects than those in the annular channel. Simple correlations between the wall factor and the blockage ratio are developed. The current research also focuses on the relationship between Reynolds number (Re) and drag coefficient (CD). The wall effect is considered while estimating the hollow frustum particle's drag coefficient (CD). The numerical estimate of the experimental drag coefficient is made using Ansys- fluent 18.1, and the experimental and numerical results are consistent with each other.

Analysis of strength characteristics of loess before and after freezing using a hollow cylinder torsional shear apparatus

This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development. In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle (α) reduces the strength of the generalized shear stress and shear strain curves. Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient (b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.

Micromechanical modeling of hollow cylinder torsional shear test on sand using discrete element method

Previous studies on the hollow cylinder torsional shear test (HCTST) have mainly focused on the macroscopic behavior, while the micromechanical responses in soil specimens with shaped particles have rarely been investigated. This paper develops a numerical model of the HCTST using the discrete element method (DEM). The method of bonded spheres in a hexagonal arrangement is proposed to generate flexible boundaries that can achieve real-time adjustment of the internal and external cell pressures and capture the inhomogeneous deformation in the radial direction during shearing. Representative angular particles are selected from Toyoura sand and reproduced in this model to approximate real sand particles. The model is then validated by comparing numerical and experimental results of HCTSTs on Toyoura sand with different major principal stress directions. Next, a series of HCTSTs with different combinations of major principal stress direction (α) and intermediate principal stress ratio (b) is simulated to quantitatively characterize the sand behavior under different shear conditions. The results show that the shaped particles are horizontally distributed before shearing, and the initial anisotropic packing structure further results in different stress–strain curves in cases with different α and b values. The distribution of force chains is affected by both α and b during the shear process, together with the formation of the shear bands in different patterns. The contact normal anisotropy and contact force anisotropy show different evolution patterns when either α or b varies, resulting in the differences in the non-coaxiality and other macroscopic responses. This study improves the understanding of the macroscopic response of sand from a microscopic perspective and provides valuable insights for the constitutive modeling of sand.

Design of a Flexure-Based Flywheel for the Storage of Angular Momentum and Kinetic Energy

The flywheel is a widespread mechanical component used for the storage of kinetic energy and angular momentum. It typically consists of cylindrical inertia rotating about its axis on rolling bearings, which involves undesired friction, lubrication, and wear. This paper presents an alternative mechanism that is functionally equivalent to a classical flywheel while relying exclusively on limited-stroke flexure joints. This novel one-degree-of-freedom zero-force mechanism has no wear and requires no lubrication: it is thus compatible with extreme environments, such as vacuum, cryogenics, or ionizing radiation. The mechanism is composed of two coupled pivoting rigid bodies whose individual angular momenta vary during motion but whose sum is constant at all times when the pivoting rate is constant. The quantitative comparison of the flexure-based flywheel to classical ones based on a hollow cylinder as inertia shows that the former typically stores 6 times less angular momentum and kinetic energy for the same mass while typically occupying 10 times more volume. The freedom of design of the shape of the rigid bodies offers the possibility of modifying the ratio of the stored kinetic energy versus angular momentum, which is not possible with classical flywheels. For example, a flexure-based flywheel with rigid pivoting bodies in the shape of thin discs stores 100 times more kinetic energy than a classical flywheel with the same angular momentum. A proof-of-concept prototype was successfully built and characterized in terms of reaction moment generation, which validates the presented analytical model.

Harmonic oscillations of a piezoceramic functional-graded sectional cylinders with account of energy dissipation

Harmonic oscillations of piezoceramic functional-gradient sectioned hollow cylinders are studied, taking into account energy dissipation. A cylinder of finite length is considered, consisting of an even number of sections polarized in the circular direction, which are connected to each other by similar sides. The material is considered to be functionally heterogeneous in the direction of the previous polarization. The cylinder is loaded by the potential difference applied to the flat faces of the sections. The calculation is performed by the finite element method. The forming of damping matrix and determining the coefficients corresponding to the four ways of introducing Rayleigh damping into the FEM is described. Amplitude-frequency responses taking into account damping are built for displacements, charge on the electrodes, electrical admittance and its logarithm. The consideration of energy dissipation according to the Rayleigh damping model is related to the experimental data due to the Q factor of the piezo element. The frequencies of electrical resonances, anti-resonances and the corresponding electromechanical coupling coefficients for functionally inhomogeneous and homogeneous cylinders are determined. For the functional-gradient piezoelectric element of the considered configuration, the maximum CEMC occurs at the frequency of the second electrical resonance. At this frequency, the dynamic stress-strain state of the cylinder is investigated. Forms of oscillations and distribution of stress amplitude values are constructed. The largest normal stresses according to the Coulomb-Mohr strength theory are determined and compared with the von Mises strength theory. FEA allows three-dimensional calculation of harmonic oscillations of functional-gradient piezo elements of complicated geometry. The determined frequencies of electrical resonance and anti-resonance and the corresponding CEMC make it possible to choose the most effective operating mode of the piezo element. The FEM mathematical apparatus makes it possible to quickly and qualitatively evaluate the strength, determine the charge on the electrodes, the current in the circuit, build the amplitude-frequency characteristics of admittance and impedance, and evaluate the efficiency of energy conversion.

Conjugate Mixed Convection of a Micropolar Fluid Over a Vertical Hollow Circular Cylinder

This work conducts a numerical examination into the influence of a magnetic field and viscosity dissipation on the movement of a micropolar fluid over the surface of a vertical, hollow circular cylinder via conjugate mixed convection. In this investigation, we obtained a numerical solution for a non-linear differential equations-based modeling system by employing MATLAB and the bvp4c solver, which operates on a two-equation model. We show graphically how micropolar materials, conjugate heat transfer, viscous energy dissipation, buoyancy factors and magnetic field affect the temperature at the interface, local skin friction and heat transfer. By contrasting the acquired results with those found in the published research, which exhibit a high degree of concordance, the validity of the methodology is proven.

3,4-Ethylenedioxythiophene Hydrogels: Relating Structure and Charge Transport in Supramolecular Gels.

Ionic charge transport is a ubiquitous language of communication in biological systems. As such, bioengineering is in constant need of innovative, soft, and biocompatible materials that facilitate ionic conduction. Low molecular weight gelators (LMWGs) are complex self-assembled materials that have received increasing attention in recent years. Beyond their biocompatible, self-healing, and stimuli responsive facets, LMWGs can be viewed as a "solid" electrolyte solution. In this work, we investigate 3,4-ethylenedioxythiophene (EDOT) as a capping group for a small peptide library, which we use as a system to understand the relationship between modes of assembly and charge transport in supramolecular gels. Through a combination of techniques including small-angle neutron scattering (SANS), NMR-based Van't Hoff analysis, atomic force microscopy (AFM), rheology, four-point probe, and electrochemical impedance spectroscopy (EIS), we found that modifications to the peptide sequence result in distinct assembly pathways, thermodynamic parameters, mechanical properties, and ionic conductivities. Four-point probe conductivity measurements and electrochemical impedance spectroscopy suggest that ionic conductivity is approximately doubled by programmable gel assemblies with hollow cylinder morphologies relative to gels containing solid fibers or a control electrolyte. More broadly, it is hoped this work will serve as a platform for those working on charge transport of aqueous soft materials in general.

Estimation of heat transfer and thermal conductivity of particle-reinforced hollow cylinder composites

With the expansion of seabed gas hydrate exploitation, particle-reinforced cement is widely used in well cementing. However, the estimation of heat transfer and thermal conductivity for hollow cylinder composites reinforced with particles remains ambiguous and requires further clarification. This paper employs the inclusion-based boundary element method (iBEM) to calculate both the local field distribution and effective thermal properties of particle-reinforced hollow cylinder composites (PRHCC). Particle interactions are simulated through the introduction of the eigen-temperature gradient, and the boundary effect is modeled using the boundary element method. Numerical simulations explore the influence of interparticle interactions, particle volume fraction, particle properties, and particle distribution on the thermal properties of PRHCC. The results show that the particle interactions have distinct effects in different directions, significantly altering the temperature spread in the central and lower regions within the particles, and then affecting the overall thermal properties of PRHCC. This method serves as a valuable reference for the engineering industry, providing insightful guidance for optimizing design, fabrication processes, and material selection, particularly in components with thermal considerations.

Shear fatigue behaviour of interfaces between bituminous layers using 2T3C hollow cylinder apparatus and Digital Image Correlation

Evaluating the shear fatigue behaviour of the interface between two bituminous layers is important in order to assure the structure can withstand repeated loadings. The 2T3C (Torsion-Traction-Compression sur Cylindre Creux, in French) hollow cylinder apparatus developed at the University of Lyon/ENTPE can apply torsion, tension, and compression on hollow cylinder samples. In this study, the apparatus is combined with 3D Digital Image Correlation (3D-DIC) to study the fatigue behaviour of the double-layered hollow cylinder samples with the interfaces with a tack coat made of emulsified bitumen. The fatigue failure was observed at the interfaces and not in layers. Six fatigue criteria are proposed to determine the fatigue life of an interface. They are: (1) the 50% reduction of stiffness criterion; (2) the maximal phase angle criterion, (3) maximal dissipated energy criterion, (4) slope change in the dissipated energy evolution curve criterion, (5) slope change in the stress evolution curve criterion, and (6) slope change in the displacement gap at the interface evolution curve criterion. The first criterion is more conservative in comparison with the last five criteria.

Development of a novel extrusion device to improve the printability of 3D printable geopolymer concrete

This study explores the printability of 3D geopolymer concrete using a novel extrusion device. Geopolymer, known for its eco-friendliness and rapid curing, offers an eco-friendly alternative to conventional cement in 3D printing. A novel extrusion device, integrating mixing and stirring functions, was developed to blend sodium silicate powder and precursor slurry effectively. Systematic experiments on mixing ratio, time, and speed revealed optimal conditions for geopolymer concrete printability. The precursor slurry remained pumpable for 90 min and displayed rapid reactivity in the new device. The extruded geopolymer concrete exhibited exceptional buildability, reaching a remarkable yield strength growth rate of 931.69 Pa/s. Actual printing tests resulted in a 154-layer hollow cylinder, 1840 mm tall, printed in just 26.87 min. Increasing mixing time enhanced compressive strength and reduced porosity, showcasing the potential of this set-on-demand approach and the novel extrusion device in 3D printable geopolymer concrete applications.

Hydraulic characterization and start-up of a novel circulating flow bio-carriers

High-quality biofilm carriers are crucial for the formation of biofilm, but problems such as slow biofilm growth on the carrier surface have been troubling a large number of researchers. The addition of a carrier changes the flow state in the reactor, which in turn affects the microbial attachment and the quantity of microorganisms. Also, aerobic microorganisms need to use dissolved oxygen in the water to remove water pollutants. In this paper, a novel recirculating flow carrier with a hollow cylinder structure is proposed, with a certain number of hollow inverted circular plates placed at equal distances inside. In this paper, the hydraulic residence time, aeration volume, and the spacing of the inflow plates of the recirculating flow biofilm carrier, which are three important factors affecting the hydraulic characteristics of the reactor, are first investigated. At the same time, it was compared with the common combined carrier to find the optimal operating conditions for the hydraulic characteristics. Secondly, a reactor start-up study was carried out to confirm that the new recirculating flow biofilm carrier could accelerate the biofilm growth by changing the hydraulic characteristics. The results showed that under the same conditions, the hydraulic properties of the reactor were better with the addition of the recirculating flow carrier, with an effective volume ratio of 98% and a significant reduction in short flows and dead zones. The stabilized removal of COD, NH3-N, and TN in the reactor with the addition of the recirculating flow carrier reached about 94%, 99%, and 91% respectively, at the beginning of the 15th day, which effectively proved the feasibility of the recirculating flow carrier.

Increasing evaporation in a solar still using a revolving hollow cylinder as an evaporation surface

ABSTRACT The main problem hindering the implementation of traditional solar stills is their low productivity. This research aims to enhance the performance of solar stills by employing a rotating hollow cylinder. The impact of the cylinder’s rotation speed on the still’s productivity and efficiency was studied using five rotational speeds (0.05, 0.1, 0.5, 1, and 2 rpm). The influence of covering the cylinder surface with fabric on the solar still’s performance was also investigated, highlighting the optimal rotation speed in both cases. Results showed a 43% improvement in the solar still’s productivity using the unclothed cylinder at a rotation speed of 0.5 rpm compared to the traditional still. Moreover, the clothed cylinder demonstrated a 65% enhancement at a rotation speed of 0.1 rpm. The better rotation speed for the unclothed cylinder found to be 0.5 rpm, while for the clothed cylinder 0.1 rpm.

Viable route to the manufacture of short carbon fiber-rich UHTC complex shapes with enhanced toughness

ZrB2 - based pasted, containing 5, 20, 45, 60 vol% short carbon fibers (Cf), were prepared in order to obtain complex shapes via direct ink writing, which were then sintered by hot pressing. The rheological behavior of the pastes indicated that at low Cf concentrations, the fibers act as a lubricant decreasing the paste viscosity. Above 20 vol% Cf, they act also as a binder creating an interconnected network that dominates over the lubrication effect, resulting in a viscosity increase. Complex shapes in the form of a hollow cylinder and a winglet with a functionally graded composition were then extruded and hot pressed, using a versatile powder bed method that enabled full densification with no need to use ad-hoc machined graphite inserts. Bars obtained from the direct ink writing process resulted in high alignment of the short fiber and displayed fracture toughness increase of 54% over that of the unreinforced matrix, while demonstrating a 42% increase with respect to conventionally hot pressed dry mixtures of ZrB2 and short fibers.This work shows the great potential of manufacturing complex shapes in ultra-high temperature ceramics matrices reinforced with short fibers for a plethora of design possibilities, including functional grading with control over layer composition, thickness and even alignment of short fiber.

Lateral compressive behavior of multi-layer lattice-web reinforced composite cylinders

Several novel multi-layer lattice-web reinforced composite cylinders, consisting of glass fiber reinforced polymer (GFRP) face sheets and lattice webs, polyurethane (PU) foam core and clay ceramsite filler, were proposed and manufactured using a vacuum assisted resin infusion process (VARIP) method. A series of quasi-static lateral compressive experiments were carried out to investigate the feasibility of the proposed cylinders. For both the hollow composite cylinders and ceramsite filling composite cylinders, the bearing capacity and energy absorption performance can be significantly improved with the use of multi-layer lattice-web layouts. Among the proposed three types of lattice-web layouts, the double-layer dislocated lattice-web layout made the composite cylinder exhibit the greatest specific energy absorption (SEA) performance and can be chosen as an optimal configuration. Furthermore, numerical models were established using LS-‍DYNA software to simulate the large deformation of the composite cylinders with double-layer dislocated lattice-web layout. Based on the numerical models, parametric analysis was carried out to discuss the effects of various parameters on the crushing response of the composite cylinders. Generally, using thicker GFRP material or higher radial lattice web can make the composite cylinders present an increased likelihood of brittle failure. However, filling ceramsite can not only make them exhibit plastic deformation characteristics but also facilitate the full utilization of various components.

Sustainability and Resiliency Investigation of Grouted Coupler Embedded in RC ABC Bridge Pier at Vehicle Impact

Increased occurrences of natural and man-made dynamic loading caused by high strain rate dynamic impact load have been recently reported. Different statistical results indicate that vehicular impacts occur more frequently compared to the other dynamic loads. However, existing literature primarily focuses on enhancing survivability and determining damage levels specifically in relation to faster bridge construction methods used as an accelerated bridge construction (ABC). In this context, the present study investigates the dynamic behavior of a commonly used connection type in ABC, namely grouted coupler that connects pre-cast elements like bridge piers and foundations. To execute the research, both the static and dynamic performance of grouted couplers embedded in pier foundation subjected to high strain rate loading incurred by high velocity vehicular impact are examined. A representative non-traditional reinforced concrete (RC) bridge pier is selected for the study with the standardized geometry and selected material properties. The use of splice sleeves as coupler materials and specified cross-sectional hollow cast iron cylinders filled with high strength concrete grout is employed for developing Finite Element (FE) modeling, extracting data from published journals. A commercial software, ANSYS, has been utilized to develop FE models to capture post impact respective static and dynamic behaviors, and the simulation results are then compared with the analytical. This also includes determining material performance via FE simulations. By considering dynamic loading, the dynamic impact factor (DIF) has been evaluated for the reinforcing steel bar adjacent and embedded into the coupler. In addition, dynamic simulations, and material modulus in demand to sustain impact are determined. Thus, the research necessitates mesh-independent sensitivity studies to investigate DIF corresponding to the precise outcomes. The findings of this study manifests valuable information that aids to opt for the suitable coupler connections, considering material properties, and adequate post impact execution. Consequently, it will serve as a useful design tool for design offices, structural practitioners, and forensic structural engineers.

Geometry impact on fundamental properties of theophylline-containing SLS printed pharmaceutical tablets

Selective Laser Sintering (SLS) has the potential to offer a more accurate alternative to current-practice manipulation of oral dosage forms for pediatric, geriatric, and dysphagia-suffering patient groups. In order to create the best possible dosage forms for these patient groups, an in-depth look into how a dosage forms geometry impacts the overall properties is essential. In this study, the impact of geometry on SLS manufactured oral dosage forms on the tablet’s microstructure, actual-to-theoretical volume, mass deviation, disintegration, and dissolution was investigated. Three different shapes; cylinder, hollow cylinder, and conical frustum with similar surface area (SA), as well as three cylinders with different diameters, were investigated. The results indicate that the geometry has an impact on the mass uniformity, resultant volume, disintegration, and dissolution properties of the tablets. The mass uniformity analysis of the tablets provided the most variation between tablets of different sizes, with more uniformity for tablets with similar SA-to-volume ratio (SA/V). When examining the actual-to-theoretical volume of the tablets, a greater variance between the actual and theoretical volumes for shapes with higher overall SA was observed. The values found are approximately 1.05 for the three differently sized cylinders, 1.23 for the conical frustum, and 1.44 for the hollow cylinder, following this trend. Disintegration data supported a link between SA/V and average disintegration time, observed with the tablet of the highest SA/V disintegrating in 12 s and the tablet with the lowest SA/V disintegrating in 58 s. Dissolution results also indicated a strong dependence on SA/V. Hence, when novel ways to produce oral dosage form tablets become available by additive manufacturing, such as SLS, both geometry and SA/V must be taken into consideration in the tablet design process to ensure appropriate release kinetics and dosing standards.

Dynamic flyer in barrel imaging via high intensity short-pulse laser.

The thin flyer is a small-scale flying object, which is well known as the core functional element of the initiator. Understanding how flyers perform has been a long-standing issue in detonator science. However, it remains a significant challenge to explore how the flyer is formed and functions in the barrel of the initiator via tabletop devices. In this study, we present dynamic and unprecedented images of flyer in barrel via high intensity short-pulse laser. Advanced radiography, coupled with a high-intensity picosecond laser X-ray source, has enabled the provision of state-of-the-art radiographs in a single-shot experiment for observing micron-scale flyer formation in a hollow cylinder in nanoseconds. The flyer was clearly visible in the barrel and was accelerated and restricted differently from that without the barrel. This first implementation of a tabletop X-ray source provided a new approach for capturing dynamic photographs of small-scale flying objects, which were previously reported to be accessible only via an X-ray phase-contrast imaging system at the advanced photon source. These efforts have led to a significant improvement of radiographic capability and a greater understanding of the mechanisms of "burst" of exploding foil initiators for this application.

Modeling the mechanical behaviour of fibre reinforced sands

ABSTRACT The mechanical behaviour of Fibre-reinforced sands (FRS) has been extensively studied, presenting improved mechanical properties compared to unreinforced soils. Many models have been developed to predict its general stress-strain behaviour. However, the use of double-phase models in FRS is still incipient. Double-phase models are advantageous because they can simulate the whole FRS and the behaviour of its individual components, soil skeleton and reinforcement. This paper uses a modified model for Municipal Solid Waste to reproduce the FRS mechanical response. Introducing a new hardening parameter and a dilatant zone allowed the model to reproduce FRS dilatancy. The model’s variables are easily understood, allowing the reproduction of the mechanical behaviour of FRS formed by sands with void ratios ranging from 0.610 to 0.917 and mean grain size from 0.29 to 0.83 mm. The fibres’ lengths varied from 12.5 to 51 mm. The results of triaxial and hollow cylinder torsional tests under different stress paths had their main characteristics (peak strength, post-peak behaviour, dilatancy and reinforcement effectiveness) well captured by the model. Predicted and experimental FRS’s deviator stress usually differ by less than 15% and the model performance is equivalent or superior to other available models, even requiring fewer input parameters.

Variational construction of tubular and toroidal streamsurfaces for flow visualization

Approximate streamsurfaces of a three-dimensional velocity field have recently been constructed as isosurfaces of the closest first integral of the velocity field. Such approximate streamsurfaces enable effective and efficient visualization of vortical regions in three-dimensional flows. Here we propose a variational construction of these approximate streamsurfaces to remove the limitation of Fourier series representation of the first integral in earlier work. Specifically, we use finite-element methods to solve a partial differential equation that describes the best approximate first integral for a given velocity field. We use several examples to demonstrate the power of our approach for three-dimensional flows in domains with arbitrary geometries and boundary conditions. These include generalized axisymmetric flows in the domains of a sphere (spherical vortex), a cylinder (cylindrical vortex) and a hollow cylinder (Taylor–Couette flow) as benchmark studies for various computational domains, non-integrable periodic flows (ABC and Euler flows) and Rayleigh–Bénard convection flows. We also illustrate the use of the variational construction in extracting momentum barriers in Rayleigh–Bénard convection.

CFD Analysis of Buoyancy-Driven Flow in an Infinite Surrounding: Comparison of Effects of Solid and Hollow Cylinders

CFD Analysis of Buoyancy-Driven Flow in an Infinite Surrounding: Comparison of Effects of Solid and Hollow Cylinders