Cylinder Radius Research Articles

Model-based cylinder radius and permeability estimation using eddy current testing

The material quality of metallic cylinders including microstructure is reflected in their physical properties. Eddy current testing techniques play an important role in the measurement of metallic cylinder measurement. In this paper, a cylinder radius and permeability estimation method is proposed based on the combined analytical and optimisation method. The Dodd and Deeds analytical model has been first simplified, which suggests an approximate linear relationship between the cylinder radius, permeability and coil inductance. Based on the proposed relation, the pre-estimated radius and permeability are used as the initial guess for the modified Newton–Raphson algorithm to solve the least squares problem between the measured and calculated coil inductance spectra. This method avoids the local minimum issue that occurs otherwise, to some extent. The effectiveness of the proposed method has been evaluated by numerical simulations and experiments, which indicates that fast estimation can be achieved with high accuracy.

Properties of Scattering Fields from Gaussian Beam Incident on Rough Cylinders

At present, most researchers focus on plane wave incident on targets, but in practical applications, most of the beams are Gaussian beam. We study the scattering fields of Gaussian beam incident on rough cylinders. Coherent and incoherent scattering coefficients are obtained based on the angular spectrum expansion and physical optics approximation, and the effects of cylinder roughness, beam radius, cylinder radius and angle of incidence on scattering coefficients are analyzed. The results show that, for a constant wavelength, when the root mean square height is greater than or equal to 1/5 of the wavelength, the coherent scattering coefficient curve undergoes a change in its distribution, with the peak transforming into a trough. Furthermore, when the root mean square height is greater than or equal to 1/3 of the wavelength, the incoherent scattering coefficient experiences a decline as the root mean square height increases. The correlation length only affects the incoherent scattering coefficient. Both the coherent and incoherent scattering coefficients decrease with the increase in the incident angle. Finally, when the roughness and incident angle are constant, with the increase in the ratio of the cylinder radius to the beam waist radius, the scattered light field is more concentrated. Our results provide the theoretical basis for the measurement of the cylindrical scattering field.

Numerical study of flow characteristics of tornado-like vortices considering both swirl ratio and aspect ratio

Flow characteristics of tornado-like vortices are primarily influenced by the swirl ratio and aspect ratio. This study systematically investigates effects of these two essential parameters on vortex visualization, mean flow fields, and fluctuations by large eddy simulations (LES). The geometric dimensions of a tornado-like vortex simulator are characterized by the inner cylinder radius and floor height. The former affects the core radii where maximum tangential velocities occur, as well as the vortex type which is used to separate flow structures while the latter influences the vortex type. Furthermore, the ratios of flow characteristics of tornado-like vortices, such as radial distances where the maximum tangential and radial velocities occur, to the inner cylinder radius (RV.max/r0; RU.max/r0, Rc/r0) have a high correlation with the swirl ratio. The ratios of heights where the maximum tangential and radial velocities occur to the floor heights (ZV.max/H0; ZU.max/H0) are mainly related to the aspect ratio. These parameters can be expressed by the swirl ratio and aspect ratio with high R-squared values of 0.941, 0.794, 0.984, 0.964, 0.958. Finally, vortex types can be modeled as a function of both swirl ratio and aspect ratio. This study reveals the relationship between the simulator geometry and generated vortices.

A multi-scan refinement technique combining cone-beam tomography and laminography

In a fine-focus geometry, for a given detector, the resolution achievable by conventional tomographic region-of-interest (ROI) imaging is limited by the smallest possible distance of the radiation source from the rotation axis, i.e., the radius of the smallest cylinder about the rotation axis that encloses the object. In situations where the specimen to be imaged is irregularly shaped, or the ROI is off-centre, higher magnification can only be achieved from a limited range of angles, (possibly in a separate scan), and a tomographic reconstruction technique able to incorporate this additional data would be advantageous. Here we present such a technique for imaging planar (or laminar) objects based on a combination of multiple tomography and laminography scans with increasing magnification that employ helical and planar source trajectories respectively. Relative to laminography, this hierarchical combination improves depth resolution, (longitudinal direction), as well as reducing imaging artefacts. Relative to full-field tomography the proposed method increases resolution, particularly in the plane of the specimen, (transverse direction). The foundation of the technique is a generalisation of accelerated multi-grid tomographic reconstruction methods to the case of multiple independent collections of radiographs. Here we first demonstrate the concepts and performance of this technique through a simulated example. We then demonstrate the successful application of the method experimentally to a thin rock section and a printed circuit board.

Numerical study of light scattering and propagation in soymilk: Effects of particle size distributions, concentrations, and medium sizes

Understanding light scattering and propagation in soymilk is crucial for the nondestructive evaluation of food qualities of soymilk and its products by near-infrared spectroscopy. We aim to numerically examine light scattering and propagation in soymilk samples with different solid-content properties (particle size distributions and concentrations) and medium sizes. Using the dependent scattering theory, we calculated the light-scattering properties of the samples on the sub-nanometer scale. In contrast, we calculated light propagation on the millimeter scale using the radiative transfer theory. Our numerical results show that the scattering properties of soymilk strongly depend on the solid-content properties, implying a high correlation between the solid-content and scattering properties. The sample with the largest mean diameter and broadest size distribution has the smallest reduced scattering coefficient among the samples, although it has the largest scattering coefficient. We compared the reflected fluence rates in a cylinder and semi-infinite medium. The comparative study shows the finite size effect on light propagation can be negligible at the cylinder radius of more than 2.0 cm. In that case, the light propagation model for a semi-infinite medium is a better choice to provide fast calculations in inverse analysis on the scattering properties. Our findings are essential for further developing near-infrared spectroscopy using scattered light and the physics of light scattering in dense polydisperse media.

Repeated falling-head method for in situ measurements of saturated hydraulic conductivity using a single cylinder

A simple, repeated falling-head (RFH) method, which uses an inexpensive portable cylinder to quickly determine field-saturated hydraulic conductivity (Kfs), is presented. A cylinder of radius r, inserted vertically from the soil surface to a depth d, is used as a water supply tank, through which water infiltrates into the soil. The falling-head test is repeated without allowing the cylinder to be drained entirely to eliminate the effects of the initial soil moisture conditions. Either change in the water level (H) in the water supply cylinder or strong linearity between the infiltration flux (qs) and H can be used to determine Kfs directly or by multiplying the slope with an empirical ring-installation scaling length, Lg; thus, no soil-dependent variable is necessary. To obtain the Lg value for various conditions, we carried out numerical experiments using HYDRUS (2D/3D) with a recently implemented reservoir boundary condition for six different soil textures, ranging from coarse soil (e.g., sand) to fine soil (e.g., silty clay loam), and two different ranges of water levels, 15 ≤ H ≤ 25 cm and 2 ≤ H ≤ 6 cm. Numerical results showed that the Lg has a strong linear dependence on d and r, where Lg increases as d and r increase. We propose a new linear model to determine Lg with optimized coefficients for each H range. Numerical results showed no significant differences in the estimated Kfs after the second repetition, confirming that repeating the falling head test twice is sufficient. The newly obtained Lg values were then applied to the experimental data obtained at multiple fields having different soil textures. The Kfs values determined using the RFH method agreed well with those measured using the field two-ponding depths steady-state method and/or the FH method in the lab. These results demonstrate the reliability of the proposed RFH method.

Novel and Efficient Methodology for Drop Placement Accuracy Testing of Robot-Guided Inkjet Printing onto 3D Objects

Robot-guided inkjet printing technology offers a new way for the digital and additive deposition of low-viscous inks to be made directly onto arbitrary surfaces and, thus, enables the production of individualized printed electronics on large-scale objects. When compared to conventional flatbed printing, the distance between the nozzle plate and the object’s surface varies and needs to be considered in order to match the accuracy requirements needed for the positioning of single drops. Knowledge about applicable distance limits and the influence of tunable print parameters is crucial for improving the print process and results. This study discusses the sources of errors in the inkjet printing process onto 3D objects and presents extensive results about position accuracy in relation to jetting distance for different parameter sets of functional inks, drop volumes, and piezo voltages. Additionally, an efficient novel method was applied to determine the drop position accuracy of inkjet droplets in relation to the jetting distance. The method relies on cylinder geometry for the object and an inkjet head that is guided by a six-axis robot manipulator along the cylinder’s axis. For the determination of drop placement accuracy, the position of single dots on the surface was compared to a model which considered the cylinder radii, drop velocity, and the movement speed of the guided inkjet printhead. The method and the extensive research results can be utilized for the prediction of achievable drop placement accuracy and the prior definition of distance limits.

Novel method to establish equation of ZN helicoid and meshing limit line of related worm drive

According to the definition, the straight sided normal profile helicoid is established. It is strictly proved that the normal section of straight sided normal profile helicoid is straight line and the cross-section is extended involute, and the section curve of axial section is obtained. The calculation formula of the guide cylinder radius under different installation modes of ZN-type worm is obtained. The meshing limit line equation of uniform speed vertical staggered shaft drive is derived, make the calculation formula of meshing limit line more simple. The meshing equation and the meshing limit line equation of ZN-type worm drive are derived. Through theoretical calculation, it is verified that the meshing limit line is the inherent characteristic of ZN-type worm pair and cannot be eliminated by modifying parameters. The meshing limit line is solved and some conclusions are drawn. The numerical results show that the meshing limit line exists on the worm tooth surface, which divides the contact area into two parts: effective area and ineffective area. The conjugate line of the meshing limit line is located in the middle of the worm gear tooth surface.

Dual resonance based on quasi-bound states in continuum in the all-dielectric terahertz metasurface and its application in sensing

In recent years, the concept of bound states in continuum (BIC) in metasurfaces has become a topic of interest. BIC involves the physical mechanics of wave optics, metamaterial sensors and other high-quality factor (Q-factor) applications. In this paper, the basic concept of BIC is introduced, followed by a brief description of the progression of the research regarding the application of BIC in terahertz (THz) metasurfaces. Subsequently, an all-dielectric metasurface consisting of tetramer clusters with dual terahertz resonances is proposed. The materials used for the substrate and the tetramer cluster are quartz and silicon, respectively. Quasi-BIC works by varying the cylinder radius on the metasurface structure. The transmission spectra are analyzed under different structural and material parameters with control variables. When the metasurface is applied as a refractive-index sensor, the Q-factor is 2303.77 and the figure of merit (FOM) is 7022.90, which are calculated using the asymmetric parameter k = 0.8 μm. Additionally, when the incident wave is x- or y-polarized, resonance peaks with the same frequencies can be obtained, and the overall trend of the transmission spectrum remains the same.

Van der Waals interaction energies for ferric ion sensors using prismatic and cylindrical pore approximations for a MOF pore.

Using the Lennard-Jones potential, we determine analytical expressions for van der Waals interaction energies between a point and a rectangular prism-shaped pore, writing them in terms of standard elementary functions. The parameter values for a new ferric ion sensor are used to compare these calculations with the cylindrical pore approximation for the interactions between an ion and a metal organic framework (MOF) pore. The results using the prismatic pore approximation predict the same qualitative outcomes as a cylindrical pore approximation. However, the prismatic approximation predicts lower magnitudes for both the interaction potential energy minimum and the force maximum, since the average distance from the centre-line to the surface of the prism is greater. We suggest that in some circumstances it is sufficient to use the simpler cylindrical approximation, provided that the cylinder radius is chosen so that the cross-sectional area is equal to the area of the prism pore opening. However, atoms at the nodes should remain approximated by semi-infinite lines. We also determine the interaction between a second ferric ion and a blocked MOF pore; as expected, the second ferric ion experiences a force away from the pore, implying that approaching ferric ions can only occupy vacant MOF pores.

Reduction of wave load on monopile-supported offshore wind turbine by a gear-type plate

This study investigates the wave diffraction problem of a vertical cylinder with a gear-type plate by using the linear wave theory and the method of eigenfunction expansion. The present model is demonstrated to be accurate, through a comparison with the numerical results of the boundary element method. The horizontal wave force acting on the cylinder can be reduced considerably by the gear-type plate. Meanwhile, the variation in bending moment at the bottom of the cylinder depends on the wave conditions and geometry parameters. A low value of the ratio between water depth and cylinder radius (d/r0) can result in an increase in the bending moment on the cylinder, rather than a decrease, due to the additional loads exerted by the gear-type plate. The bending moment on the cylinder can be reduced significantly by the gear-type plate as d/r0 increases. Within d/r0∈[4,10] of the present monopile-supported wind turbines, the wave loads on the monopile foundation can be reduced significantly by the proposed gear-type plate. Compared with a ring-type plate, a gear-type plate exhibits superior reduction effects over an equal plate area. The loads on the structures are insensitive to the wave exposure angle when the teeth number increases beyond three.

Dual convection of NEPCM inside an annulus between two circular cylinders mounted on rectangles

This paper adopts the incompressible smoothed particle hydrodynamics (ISPH) method for simulating the dual diffusion of nano-encapsulated phase change material (NEPCM) in an annulus. Here, the novelty is appearing in simulating the double diffusion of NEPCM within a novel complex shape composed from the paradigm of an annulus between two circular cylinders mounted on rectangles. The ISPH method solved the regulating equations of a physical problem. The scales of parameters are a fusion temperature θf(0.05≤θf≤0.95), buoyancy ratio 0≤N≤10, nanoparticle parameter 0.01≤φ≤0.05, a radius of a circular cylinder 0.1≤rc≤0.4, Darcy parameter 10-2≤Da≤10-5, and Rayleigh's number 103≤Ra≤106. The performed simulations showed that the different boundary conditions amongst an inner blockage and outer cavity walls are affecting the strength of concentration and temperature. The location of a phase change zone is varied according to the variations of variable boundary conditions and fusion temperature. The mean Nusselt and Sherwood numbers are improving under an enlargement in a radius of an internal circular cylinder, and Rayleigh numbers.

Enhancement of conjugate heat transfer in an enclosure by utilizing water and nano encapsulated phase change materials with active cylinder

Conjugate heat transfer in a differentially heated enclosure having an active cylinder placed at the center-line is studied numerically. The free space between the cylinder and the walls of the enclosure is filled with water (H2O) and nano-encapsulated phase change materials (NEPCMs). The governing equations take the form of a primitive formulation and are numerically solved using the finite element method. The controlling factors under consideration are the cylinder’s location, −0.2≤δ≤+0.2, the cylinder radius, 0≤R≤0.3, the rotation speed, −150≤Ω≤150, the thermal conductivity ratio, 0.5≤Kr≤10, the Rayleigh number, 104≤Ra≤106, and the NEPCMs concentration, 0≤ϕ≤0.05. The number, size, and shape of the cells change depending on where the inner cylinder is, how fast it is spinning, and how much NEPCMs are in the suspension. The placement of the peak Nusselt number values is heavily influenced by the rotational direction.

Semi-analytical study of linear waves interaction with a vertical permeable cylinder of arbitrary cross-section based on perturbation theory

ABSTRACT This paper studies linear waves incident to a vertical permeable cylinder with arbitrary cross-section based on the boundary element method and perturbation theory. Considering a near-zero thickness for the permeable media, and using Darcy's law, the governing equation for the wave incident to a porous circular cylinder is derived based on the boundary element method. Then using perturbation theory and considering a small parameter ε denoting the variation of cylinder radius from circular ones, the corresponding equations were expanded for non-circular cylinders. The developed method was applied to ellipse-shaped and rectangular cylinders. The wave forces and the wave strength inside the cylinder under a variety of parameters such as wavenumber, and porosity parameter were studied. One application of these research results is a better understanding of the behaviour of non-circular aquaculture cages in sea waves. According to the results, near-trapped modes can occur inside rectangular cages with small porosity parameters.

Frequency scanning interferometry based deformation monitoring system for the alignment of the FCC-ee machine detector interface

In a particle accelerator, two particle beams are accelerated and collided at one or several physics detectors. The machine detector interface (MDI) is the place where the accelerator ring is linked to the physics detector. It is the area where the alignment requirements are the most stringent, and the MDI of the lepton version of the future circular collider (FCC-ee) is no exception. It will implement a complex design and alignment requirement for typical components in the MDI are of the order of 30 μm. Until now, no working solutions have been proposed for the alignment of such MDI. In this contribution, two different systems are studied: the Surveillance d’Ouvrages par Fibre Optique (Structural Monitoring by Optical Fibers, SOFO) and the in-lined multiplexed and distributed frequency scanning interferometry (FSI). Both systems allow individual and simultaneous distance measurements of multiple portions along a fiber, and a new system using the FSI technology is proposed for the alignment monitoring. Using a network of helical shaped fiber allows the measurement of deformations if a sufficient amount of fibers is placed on the cylinder. With a sensor measurement accuracy of 1 μm, 3D coordinates of points at the end of a 4 m long and 0.25 m radius cylinder (FCC-ee MDI dimensions) can be determined at an accuracy under 5 μm. This system will provide a link between the alignment of the final focusing quadrupoles and the rest of the machine.

An investigation on flexural properties of anti-tetrachiral auxetic structures fabricated by material extrusion

The present paper describes an investigation on flexural properties of anti-tetrachiral auxetic structures fabricated by material extrusion technique of additive manufacturing. Flexural performance of these structures is crucial in automotive crash box, robust shock absorbers, air seat cushions, sound absorbers, air filters, airfoil morphing, biomedical stent, non-pneumatic tyres, vibration attenuation, and impact detection sensors. Mechanical properties of auxetic structure depend on geometric parameters of its unit cell. Therefore, in the present study, influence of two geometric parameters namely cylinder radius and ligament thickness on modulus, strength and specific energy absorption (SEA) of in-plane and out-of-plane oriented structures under flexural loading has been investigated. Experimental plan is prepared using central composite design method of response surface methodology. Specimens of acrylonitrile butadiene styrene (ABS) material are fabricated using material extrusion technique. Each specimen is tested under three-point flexural loading as per ASTM D790. Experimental results are analysed using analysis of variance (ANOVA). It is found that both geometric parameters influence modulus, strength and SEA of in-plane and out-of-plane oriented structure significantly. For both orientations of structure, modulus and strength increase with decrease in cylinder radius and increase in ligament thickness, while SEA increases with increase in cylinder radius and decrease in ligament thickness. Further, optimization of geometric parameters is performed using grey relational analysis to maximize the responses. Regression models are also developed to predict the responses. The findings of present study are useful in maximizing flexural properties of anti-tetrachiral auxetic structures through selection of optimum geometric parameters of unit cell.

Numerical design and optimization of metamaterials for underwater sound absorption at various hydrostatic pressures

Underwater sound absorption materials with a stable performance at various hydrostatic pressures are important for marine applications. However, most studies about underwater sound absorption materials only focused on the performance at atmospheric hydrostatic pressure, while ignoring the influence of various hydrostatic pressures. Aiming to improve the underwater sound absorption stability of a metamaterial at various hydrostatic pressures, different structures and a Nelder–Mead algorithm with an acoustic-structure fully coupled finite element method (FEM) model are developed to optimize the structure of the metamaterial at various hydrostatic pressures. In this numerical modeling, the metamaterial is a PDMS matrix embedded with periodic cylinders. Firstly, the effect of hydrostatic pressure on the metamaterial is evaluated in the frequency range [0, 8 kHz]. Secondly, different cases are designed to improve the underwater sound absorption stability at various hydrostatic pressures, including different cylinder radii, different distances between the air cylinder and the steel backing, and different void shapes. Then two layers of air and/or steel cylinders are introduced to further improve sound absorption performance under various hydrostatic pressures. The results indicate that PDMS with two layers of air cylinders have the optimal sound absorption stability performance under various hydrostatic pressures, which can be attributed to the top layer of air cylinders absorbing the main deformation. Lastly, the optimization algorithm significantly improves the sound absorption performance of the metamaterials at various hydrostatic pressures. This combination of an optimistic algorithm and FEM can guide the design of underwater sound absorption metamaterials at various hydrostatic pressures.

Oscillating viscous flow past a streamwise linear array of circular cylinders.

This paper addresses the viscous flow developing about an array of equally spaced identical circular cylinders aligned with an incompressible fluid stream whose velocity oscillates periodically in time. The focus of the analysis is on harmonically oscillating flows with stroke lengths that are comparable to or smaller than the cylinder radius, such that the flow remains two-dimensional, time-periodic and symmetric with respect to the centreline. Specific consideration is given to the limit of asymptotically small stroke lengths, in which the flow is harmonic at leading order, with the first-order corrections exhibiting a steady-streaming component, which is computed here along with the accompanying Stokes drift. As in the familiar case of oscillating flow over a single cylinder, for small stroke lengths, the associated time-averaged Lagrangian velocity field, given by the sum of the steady-streaming and Stokes-drift components, displays recirculating vortices, which are quantified for different values of the two relevant controlling parameters, namely, the Womersley number and the ratio of the inter-cylinder distance to the cylinder radius. Comparisons with results of direct numerical simulations indicate that the description of the Lagrangian mean flow for infinitesimally small values of the stroke length remains reasonably accurate even when the stroke length is comparable to the cylinder radius. The numerical integrations are also used to quantify the streamwise flow rate induced by the presence of the cylinder array in cases where the periodic surrounding motion is driven by an anharmonic pressure gradient, a problem of interest in connection with the oscillating flow of cerebrospinal fluid around the nerve roots located along the spinal canal.

Effect of heat transfer on peristaltic flow of Newtonian fluid through eccentric cylinders

Heat transfer effect on peristaltic Newtonian flow in an annular region of eccentric cylinders is considered. An approximate solution for temperature and velocity is obtained using perturbation technique. For constant flow rate, the variation of pressure gradient and velocity with respect to several non-dimensional parameters is studied using graphical representation. It is seen in these graphs that velocity, pressure gradient and temperature enhance with raise in eccentricity and amplitude ratio. Heat diffuses with faster rate with depletion in area of cross section eccentric annulus through parameter inner cylinder radius. Also, velocity rises with increase in heat transfer parameters such as Grashof number and heat transfer co-efficient. Thus velocity of peristaltic flow in eccentric annulus enhances rapidly in presence of heat transfer compared to absence of heat transfer. A study of peristaltic flow in concentric annulus in presence of heat transfer is obtained analytically and compared with present study at eccentricity equal to zero, to validate the approximate solution. It is seen that flow rate increases more in case of eccentric annulus compared to concentric in presence of heat transfer. Present study has application in endoscope, which is important to diagnose problems in internal organs. Also, the variation of pressure gradient helps to maintain flow rate which is essential during insertion of catheter into artery.

Interactions between solid–fluid particles during thermosolutal convection of a rotating cylinder in a cavity

The ISPH method is adopted to simulate the diffusion of solid particles through a nanofluid flow during the dual rotation of two circular cylinders inside a cavity. Half of the solid particles are carrying and the others carry . The novelty of this work is in simulating the dual rotation of circular cylinders with the dispersion of solid particles below the influences of Soret-Dufour numbers. The major outcomes revealed that the interactions between solid particles and nanofluid flow are enhanced according to an increase in Soret/Dufour numbers. Increasing the Hartmann number declines the interaction process between solid particles and nanofluid flow. The radius of a circular cylinder is working well in changing the transport of heat/mass within a cavity due to the variations in the total number of solid particles. The values of Nusselt and Sherwood numbers are influenced by physical factors.