Elliptic Cylinder Research Articles

Independent adjustment of the transmission amplitude and phase based on the double-sided all-dielectric encoding metasurface

In order to achieve high-efficiency and independent control of the amplitude and phase of light transmitted from the coded metasurface, we propose a double-sided all-dielectric unit structure. The all-dielectric metasurface unit structure is composed of a silicon dioxide substrate with silicon elliptical cylinder and silicon cylinder on both sides. The phase of the transmitted light can be adjusted by rotating the elliptical cylinder, and the amplitude of the transmitted light can be adjusted by changing the radius of the cylinder. In order to obtain the ideal amplitude and phase control, we set the initial rotation angle of the elliptical cylinder to eliminate the additional phase, which is caused by the radius change of the nanocylinder. We can digitally encode the unit structure of the elliptical cylinder with different rotation angles to construct different sequences of encoded metasurfaces. By adjusting the structural parameters of the encoded particles in the encoding metasurface, the amplitude and phase of the transmitted beam can be independently adjusted. The independent modulation of amplitude and phase of coding particles is verified by the far-field scattering characteristics of different coding metasurfaces.

Optical pulling force upon elliptical cylinder nanoparticles in the infrared range

In order to investigate optical pulling forces exerted by an electromagnetic field, we develop a theoretical framework based on electrostatic theory and Maxwell stress tensor. We apply this framework to calculate the optical pulling force on elliptical cylinder nanoparticles with gain medium, which we put forward as an alternative material platform to optimize and tailor tractor beams. Moreover, the optical force can be further enhanced and flexibly tuned by controlling the physical and geometrical parameters of the proposed structure. The pulling and pushing force could be switched by changing the location of the hemisphere witch has complex susceptibility in the structure. Altogether, our theoretical findings can pave the way to increase the use of this structure for further applications based on active nanoparticles

A comprehensive investigation of vortex-induced vibrations and flow-induced rotation of an elliptic cylinder

This work finds its motivation in heat exchanger design and flow control. Flow-induced vibration is studied numerically for combined vortex-induced vibrations and vortex-induced rotations of a horizontally positioned elliptic cylinder. The aspect ratio is taken as 2, and the value of reduced velocities (Ured) considered for the present simulation is between 2 and 12. The body can have to and fro motions in a transverse (y) direction, in-line (x) direction as well as in azimuthal (θ) direction, which provides three degrees of freedom (DOF) to the body. It is found that for one-DOF (y-direction only) and two-DOF (y and x directions) cases, lock-in regions are the same while it is wider for the case of the three-DOF system. With the rotational DOF, y-directional motion is amplified and when it is compared with the one-DOF and two-DOF cases, difference in peak amplitude is about 30%. The rotational response reaches a maximum value within the synchronization regime, and the frequency behavior of rotational and transverse oscillations is showing the same characteristics. The phase difference is plotted to check their synchronization with respective forces and moments. For all DOFs and Ured, synchronized or desynchronized regions, 2S mode of vortex shedding was observed. For one-DOF and two-DOF cases, the transverse vibrational frequency ratio (fy/fn) becomes equal to unity for the range 3.75≤Ured≤5. For three-DOF, fy/fn and rotational frequency ratio (fR/fn) become close to the unity for 3.75≤Ured≤6. The three-DOF system shows smaller wake width and vortex formation length whereas the vortex strength is maximum.

Influence of fiber orientation on the microstructures of interfacial transition zones and pull-out behavior of steel fiber in cementitious composites

The reinforcement of steel fibers on cementitious composites is mainly influenced by the bonding between the fiber and matrix. The steel fibers and matrix bonding depend on the interfacial transition zone (ITZ). A major cause of ITZ formation is microbleeding, i.e., the flow of free water around steel fibers at the early stage of bleeding may cause the redistribution of water and cement particles around the fibers, leading to the formation of ITZs. The fiber orientation in the matrix affects the flow of water and further influences the microstructure of the ITZ around the steel fiber and the bonding properties. This study proposes a theoretical model based on fluid mechanics to investigate the influence of fiber orientation on cement-water suspension migration around steel fibers. The microstructure of the ITZ around the steel fiber is then estimated based on the Powers model according to the water-cement ratio distribution. Finally, the interrelationships among the fiber orientation, ITZ porosity and bond strength are established by curve fitting. The results indicate that since free water with small particles flows past the steel fiber by flowing past circular (or elliptical) cylinders, a difference in the ITZ microstructures at the upper and lower surfaces of the steel fiber arises. As the inclined angle of the fiber increases, the upper surface porosity and the average porosity of the ITZ around the steel fiber decrease, leading to an increase in the fiber-matrix bond strength.

The vortex-induced vibration of an elliptic cylinder with different aspect ratios

This study investigates the hydrodynamic characteristics of an elastically-mounted elliptic cylinder at low mass ratio m*=2 and low damping ratio ζ=0.007. The aspect ratio (AR) defined by the characteristic length in the streamwise and transverse direction varies in the range 0.5≤AR≤2.0. The dynamic response is characterized as a function of reduced velocity. The streamlined profile of the elliptic cylinder results in a delay of the vortex shedding and a diminished strength of the averaged vorticity. However, the hydrodynamic characteristics become more complicated for large ARs. Both the response amplitude and the hydrodynamic forces acting on the cylinder are enhanced as the afterbody is reduced. The PSD behaviors show the existence of four different flow regimes. Several new pertinent modes, such as 2 Po*, 2T*, etc., are captured through flow visualizations. A comprehensive analysis of the vortex shedding indicates the sub-vortices generated at the rear of the cylinder plays a key role in the formation and evolution wake modes. Besides, the time-averaged vorticity magnitude at the vortex core elucidate that despite secondary vortices account for a large proportion of the primary vortices, they only make a small contribution to the suppression of the vibration amplitude.

Natural Convection Inside a Porous Square Enclosure Embedded with Two Elliptic Cylinders

The present work investigates numerically the implication of aspect ratio of a pair of embedded heated cylinders on natural convection phenomena when they are placed inside a porous square enclosure. The transport characteristics are assessed for a range of aspect ratios of the cylinders (, 0.5, 1, 2, and 4), Darcy numbers (), and Rayleigh numbers () for a constant value of interspacing distance between the cylinders. The conduction-dominated heat transfer occurs for low-permeable porous media, i.e., (), whereas the convection-dominated heat transfer occurs for higher values of ( and ). The aspect ratio of the embedded cylinders and the physicothermal parameters alter the viscous resistance and the buoyancy force acting on the fluid medium within the porous enclosure and hence the heat transfer rate. The variations of time-averaged Nusselt number are different for the two cylinders. For the bottom cylinder the average Nusselt number monotonically increases with the increase in , whereas for the top cylinder the same decreases as long as conduction heat transfer dominates and increases rapidly once the convection heat transfer dominates.

On the Stress-Strain State of Elliptic Cylinders in the Three-Dimensional Statement

On the Stress-Strain State of Elliptic Cylinders in the Three-Dimensional Statement

Non-Newtonian fluid flow over a rotating elliptic cylinder in laminar flow regime

In this paper, a numerical investigation is done to understand the two-dimensional flow behaviorof power-law fluids past a rotating elliptic cylinder in unconfined domain. The flow field around the cylinder is calculated using ANSYS (FLUENT 15) The sliding mesh method (SMM) is used to treat moving solid–fluid boundary. The engineering parameters like drag coefficient, lift coefficient and complete kinematic variables such as stream function and vorticity have been calculated for the range of dimensionless parameters namely aspect ratio of the cylinder e=0.1 and 0.7, rotational speed (1≤α≤4), Reynolds number (5≤Re≤40) and power-law index (0.4≤n≤1.8). The emphasis has been given to see the effect of the power-law index (n) and Reynolds number (Re), rotational speed α and aspect ratio of cylinder e on flow characteristics around the cylinder in laminar flow regime. Before presenting the results, a qualitative as well as a quantitative comparison has been done between the present result and experimental and numerical result presented in the literature. Further, a detailed streamline and vorticity patterns in the vicinity of the cylinder is shown to demonstrate the wake formation phenomenon around the cylinder. The increase in rotational speed and power-law index exhibit a similar effect on wake formation phenomena. Due to rotational motion of the cylinder drag and lift coefficient vary in periodic manner with time/orientation of cylinder. The average value of drag is seen to decrease with Re and α and a complete trend is displayed with power-law index, n. The negative lift coefficient is observed due to anticlockwise motion of the cylinder for all parameters considered here. The results of this work clearly show the strong dependency of flow phenomenon around the rotating elliptic cylinder on power-law index, rotational speed, aspect ratio, and Reynolds number.

Numerical simulation of heat transfer and fluid flow around a cylinder of varying cross-section

The present paper discusses the effects of geometric parameters on mixed convective heat transfer and fluid flow in a lid-driven square enclosure fitted with an internal elliptical cylinder. The side walls of the enclosure were kept at a cold constant temperature and the lower horizontal wall, and the top moving wall were isolated thermally while the elliptical cylinder wall was sinusoidal heated. The dimensionless equations were solved with the aid of COMSOL Multiphysics software which relies on the finite element method. Simulations were performed for different Grashof numbers 103≤Gr≤105, aspect ratios 1.0≤AR≤3.0, and inclination angle of the elliptical cylinder 0°≤ϕ≤90°. Results are presented in the form of velocity streamlines, isothermal contours, and average Nusselt number. Findings from this study show that the highest heat transfer enhancement occurred when Gr=105. Also, for all the inclination angles and Grashof numbers considered, the more the surface of the ellipse exposed to flow, the greater the heat transfer enhancement. Finally, beyond AR=1.5, inclination angle of the ellipse inhibits heat transfer enhancement.

Low Computational Cost Mirror Kirchhoff Approximation for Predicting Shadowing Effect

This paper proposes a 2-dimensional low computational cost mirror Kirchhoff approximation (MKA) and the design of simulation parameters to accurately predict the shadowing gain for an arbitrarily shaped conductor cylinder. The disadvantages of the conventional MKA, such as lacking designs for the simulation parameters and a limited applicable range, have motivated the establishment of an extended MKA. The authors propose the design of the simulation parameters for MKA. The applicable range of MKA is extended to an arbitrarily shaped cylinder by multiple planes. This work finds that only the space domain of the zeroth plane and the angular spectrum domain of the last plane need separate windowing functions for accuracy and the calculation time. The details of those windowing functions are introduced, and their necessities are explained. The authors validate the proposed method for an elliptical conductor cylinder with the size of the human body at millimeter waves (17 GHz – 66.5 GHz). Simulations are conducted by changing the object’s location, direction, and frequencies. The results show that the proposed method presents a good accuracy, which has a low root-mean-square error of less than 0.5 dB by comparing it with a full-wave approach based on the method of moment. Furthermore, the calculation time is improved by 1.4 – 67.2 times by comparing it with the uniform theory of diffraction using special functions.

Mode properties of elliptical dielectric waveguide with nested eccentric hollow cylinder coated with graphene

An elliptical dielectric nanowire waveguide with a nested eccentric hollow cylinder is designed, the inner surface and the outer surface of the waveguide are both coated with graphene. The transmission characteristics of the three lowest order modes supported by the waveguide, i.e. the field distribution, the real part of the effective refractive index, the propagation length, and the quality factor, are obtained by multipole method. The results show that the three lowest order modes of the waveguide can be synthesized by the lowest order modes supported by a single cylinder and an elliptic cylinder coated with graphene. With the increase of the radius of the embedded cylinder, the three evaluation indexes of the waveguide increase slightly. The change of the semi major axis of the ellipse will slightly increase the real part of the effective refractive index, propagation length and quality factor of Mode 0 and Mode 1, while Mode2 will slightly decrease. When <inline-formula><tex-math id="M1">\begin{document}$a = {{b}} = 170\;{\rm{nm}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20212321_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20212321_M1.png"/></alternatives></inline-formula>, the performance of the circular nested circular waveguide becomes slightly worse than that of the structure in this paper. With the decrease of the semi minor axis of the ellipse, the real part of the effective refractive index, propagation length and quality factor for each of the three modes increase to a certain extent, and have the greatest impact on Mode 1. When <inline-formula><tex-math id="M2">\begin{document}${{b}} = {{a}} = 190\;{\rm{nm}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20212321_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20212321_M2.png"/></alternatives></inline-formula>, the transmission performance of the circular nested circular waveguide is not so good as that of the structure in this paper. When the distance between the inner rod and the outer rod on the right side increases, the real part of the effective refractive index for each of the three modes decreases, the propagation length and quality factor of Mode 0 and Mode1 gradually decrease, while the propagation length of Mode 2 increases slightly, and the quality factor is basically unchanged. On the contrary, the mode transmission performance can be significantly improved by increasing the working wavelength and Fermi energy and reducing the dielectric constant of elliptical dielectric nanowires. Compared with the circular dielectric nanowire waveguide nested with an eccentric hollow cylinder coated with graphene, the waveguide designed in this paper can be found to have a good transmission performance. These results are verified by the finite element method. This waveguide can provide a theoretical basis for the design, fabrication and application of nested waveguides of the same type.

Design and Experiments of a Novel Halbach-Cylinder-Based Magnetic Skin: A Preliminary Study

Robotic tactile sensing plays a vital role in realizing the precise perception of complex environments, affecting the application of robots in a wide range of industrial and household fields. However, existing tactile sensors are limited by weakly interpretable information mapping relationships. In this article, a novel Halbach-cylinder-based magnetic skin is constructed with permanent magnets and elastic rubber to address such problems. Furthermore, a highly interpretable and widely applicable method is deduced to effectively represent the skin’s information conversion as a Halbach cylinder deforms to an elliptical cylinder under external force. Experiments of simulated models and actual skins with different compressions are conducted to evaluate the proposed method. The results show that 0.24% and 0.26% relative errors in simulated and real environments, respectively, can be achieved. Our method can reach the minimum error in almost all situations compared with state-of-the-art approaches. These promising results demonstrate the method’s great potential to provide a basis for developing a practical magnetic-force mapping relationship.

Investigation of Film Boiling Over Tandem Arrangement of Elliptical Cylinders in Vertical Crossflow of Saturated Liquid

Investigation of Film Boiling Over Tandem Arrangement of Elliptical Cylinders in Vertical Crossflow of Saturated Liquid

Three-component diagnostics of swirling flow in the model of an improved four-vortex furnace

The spatial structure of a swirling turbulent flow has been investigated based on the three-component laser Doppler anemometry method in an isothermal laboratory model of a four-vortex furnace. The structure of the vortex cores of the flow with the shape of a deformed vertical elliptical cylinder is visualized using the ?minimum total pressure? criterion. The spectrum of velocity pulsations indicates the absence of unsteady periodic vortex structures, which means the occurrence of a stable vortex flow in the volume of the combustion chamber.

A new technology of thermoplastic glass bending for the manufacture of cylindrical surfaces of hard X-ray range mirrors

The paper presents a new technique for thermoplastic bending of glass. The technique makes it possible to produce cylindrical surfaces with a guide in the form of a parabola, ellipse, etc. for mirrors in the hard X-ray wavelength range (λ~0.1 nm). Three samples of the surface of an elliptical cylinder were prepared using this technique. The production time for each sample was two days. The deviation of the guide and its local angle from the calculated values for all samples does not exceed Delta y=0.5 μm and Deltaα=7·10-5 rad, respectively. It is shown that when such surfaces are etched for two hours, their accuracy can be improved by more than two orders of magnitude (Delta y=2 nm, Deltaα=5·10-7 rad). Keywords: focusing X-ray mirrors, cylindrical mirrors, multilayer structures

Новая методика термопластического изгиба стекла для изготовления цилиндрических поверхностей зеркал жесткого рентгеновского диапазона

The paper presents a new technique for thermoplastic bending of glass. The technique makes it possible to produce cylindrical surfaces with a guide in the form of a parabola, ellipse, etc. for mirrors in the hard X-ray wavelength range (λ~0.1 nm). Three samples of the surface of an elliptical cylinder were prepared using this technique. The production time for each sample was two days. The deviation of the guide and its local angle from the calculated values for all samples does not exceed Δy = 0.5 µm and Δα = 7*10-5 rad, respectively. It is shown that when such surfaces are etched for two hours, their accuracy can be improved by more than two orders of magnitude (Δy = 5 nm, Δα = 5*10-7 rad).

Three dimensional flow over elliptic cylinders arrays in octagonal arrangement

A numerical study of flow characteristics around eight elliptic cross-section cylinders in an octagonal configuration is presented. The axis ratio of elliptic cylinder is taken as 1:2. Three spacings between the cylinders (0.07 m, 0.14 m and 0.2 m), two angles of attack (α=0° and α=15°) and two Reynolds numbers (Re=4060 and Re=45800) are considered to investigate the parametric influences. The flow is modelled using three-dimensional large eddy simulation. Simulations are performed by utilizing ANSYS Fluent software. The results comprise of flow patterns and force coefficients (drag and lift). It is seen that both the drag and lift forces acting on the cylinders vary with the spacings values, angle of attack and Reynolds numbers. The lift force peaks at α=15° and Reynolds number 45800. The drag force on the upstream cylinder reaches its peak at α=0° and Reynolds number 4060. It is observed that the drag on the upstream cylinders decreases as the value of the Reynolds number increases. Contours of velocity and subgrid turbulent viscosity are also presented. Moreover, it is concluded from the present study that the effect of change in the Reynolds number on flow characteristics is more significant as compared to the change in the spacing between the cylinders.

Mechanical Properties and Microstructure Evolution of Mg-Gd Alloy during Aging Treatment

Rare-earth-containing Mg alloys are a group of widely investigated alloys due to the disperse nano-sized precipitations formed during heat treatment. The underlying formation and strengthening mechanisms of precipitation is critical for their industrial applications. In this work, we systematically studied the evolution of precipitations in a Mg-10Gd alloy, based on the atomic-scaled TEM and HAADF-STEM observations. Especially, the in-depth transition mechanism from G.P. Zone to β”, β’, βT and βM is proposed, as well as their relationships with mechanical properties. It is found that blocking effect of precipitations improves the strength significantly, according to the Orowan mechanism. The elliptic cylinder shaped β’ phase, with a base-centered orthorhombic lattice structure, provides significant strengthening effects, which enhance the hardness and ultimate tensile strength from 72 HV and 170 MPa to 120 HV and 300 MPa.

Saint-Venant torsion of orthotropic piezoelectric elliptical bar

The object of this paper is the Saint-Venant torsion of a solid elliptical cylinder made of orthotropic homogeneous piezoelectric material. We find the shape of the homogeneous orthotropic piezoelectric elliptical cross section which does not warp under the applied torque. The sizes of the orthotropic piezoelectric solid elliptical cross section, which has the maximum value of torsional rigidity for a given cross-sectional area, are also determined.

Statistical Analysis of Flow Parameters for the Graphical Simulation Outputs

System dynamics simulation software, in general, depicts graphical interpretations. The values of the parameters, on the other hand, are required for prediction. The goal of this research is to develop a novel multivariate model that can predict flow parameters while simulating flow under various scenarios. The project involves looking for variations in the streamline and constructing a new multivariate model for each elliptic cylinder system's velocity magnitude. Furthermore, the flow zones were split into three groups based on streamline behavior. As a result, utilizing simulation outputs, new models for flow zones are developed using linear and semiparametric regression. The best fitted model for each flow region was determined using mean square error (MSE), root of mean square error (RMSE), and mean absolute percentage error (MAPE). Based on the fitted smoothing curve of the velocity magnitude, a summary statistic and variability may be assessed. The presented models can be used to predict magnitude in any point of fluid flow using these models.