Axisymmetric Structures Research Articles

Effects of electrostatic nonlinearity on the rate measuring performance of ring based Coriolis Vibrating Gyroscopes (CVGs)

Electrostatic nonlinearities are the dominant source of nonlinearity in ring-based capacitive Coriolis Vibrating Gyroscopes (CVGs) and have potential to parametrically amplify the sense response of the ring resonator and enhance measurement sensitivity. This paper investigates the effects of electrostatic nonlinearities on the rate-measuring performance of a ring-based capacitive CVG. A nonlinear mathematical model is used to describe the dynamics of the drive and sense modes for a ring resonator including the presence of structural imperfection. For a conventional 8 electrode configuration it is found that the direct and mode-coupled nonlinear stiffnesses for the mode pair are generally unequal, even for perfectly axisymmetric ring structures. These differences are found to affect the scale factor, bias and quadrature error of the gyroscope, and act to split the amplitude-dependent resonant frequencies but with the presence of self-induced nonlinear parametric pumping. The interaction of these effects with small structural imperfections is demonstrated and it is shown that under certain circumstances nonlinearity is able to negate the imperfection effects.

Shape optimization method for axisymmetric disks based on mesh deformation and smoothing approaches

Axisymmetric disk structures with complex contour curves are widely used in aero-engines. The shape optimization is generally carried out to reduce the stress level of axisymmetric disks. In this article, a shape optimization method for axisymmetric disks based on radial basis function (RBF) mesh deformation and Laplace smoothing approaches is proposed. This method can obtain the optimized reduced control points selection of mesh deformation under the influence of design space based on greedy algorithm. RBF mesh deformation is used to change the axisymmetric contour shape. And after deformation, the local mesh quality is monitored and improved by Laplace smoothing. In this article, two illustrative examples used in aero-engines are carried out to validate the effectiveness of the proposed method, including an independent optimization of a turbine disk and a collaborative optimization of a turbine disk with a deflector for minimizing the maximum equivalent stress. To improve the computational efficiency, a two-dimensional (2D) axisymmetric FE model is established. Compared with initial results, optimized results in two examples obtained by the proposed optimization method reduce the maximum von Mises stress by 8.02% and 9.25%, respectively. It can be concluded that the proposed method has significant potential in the shape optimization design of axisymmetric disks.

Poroelastic modeling of pore pressure development in granular pavement layers

ABSTRACT Moisture excess in granular pavement layers can decrease pavement performance leading to moisture-related distresses. The combination of trapped water and heavy traffic loads may substantially increase pore pressure and lead to shear failure if layer hydraulic conductivity is insufficient. Currently, most pavement analysis models are unable to predict pore pressure development, so the design and evaluation methods ignore this dynamic effect which may significantly underestimate the moisture damaging effect on pavements. This paper proposes the use of Biot’s poroelasticity theory for modelling fully saturated unbound materials. The proposed methodology – Poroelastodynamic Finite Integration Technique (PEFIT) – was used to analyze axisymmetric multilayered pavement structures consisting of elastic and poroelastic layers. The model was verified and validated using a well-known commercial finite element solver and field pore pressure data, respectively. A sensitivity analysis was conducted by varying critical pavement design parameters. The PEFIT analysis of a three-layer pavement system with a poroelastic base layer has shown that a decrease in base hydraulic conductivity significantly increases the maximum pore pressure, especially for high-speed loads. Results also indicate substantial pore pressure and water movement in the base layer, which may induce a potential shear failure mechanism for unbound materials.

A Low-Cost Filament Winding Technology for University Laboratories and Startups.

This paper systematically explains the methodology and results of empirical work on the development of a low-cost filament winding technology for manufacturing axisymmetric polymer composite structures with a high length-to-diameter ratio, such as tubes, motor casings, and pressure vessels. The principal objective was to examine the experiences and most optimal practices in the development of computer-controlled equipment and auxiliary tooling for the wet filament-winding process. To preclude expensive commercial software for the automated control of a winding machine, analytical equations were derived for the winding trajectory of a four-axis filament-winding machine. The feasibility of the proposed equations was successfully validated by laying the fiber along the geodesic path marked on the surface of a cylindrical mandrel with hemispherical ends. Moreover, the carbon/epoxy cylindrical casings with hemispherical ends and port openings of the same diameter were wound to determine the thickness distribution in the hemispherical dome. The fiber volume ratio in the wound composite parts was evaluated using an optical technique.

Secular perturbations of the translational-rotational motion in a nonstationary three-body problem

A non-stationary three-body problem with axisymmetric dynamic structure, shape, and variable compression is considered. The Newtonian interaction force is characterized by an approximate expression of the force function accurate to the second harmonic. The masses of bodies change isotropically at different rates. The axes of inertia of the proper coordinate system of nonstationary axisymmetric three bodies coincide with the principal axes of inertia of the bodies, and it is assumed that their relative orientations remain unchanged during the evolution. Differential equations of translational and rotational motion of three non-stationary axisymmetric bodies with variable masses and dimensions in the relative coordinate system with the origin in the center of the more massive body are presented. The analytical expression for the Newtonian force function of the interaction of three bodies with variable masses and dimensions is given. The canonical equations of translational-rotational motion of three bodies in the Delaunaye-Andouye analogues have been obtained. The equations of secular perturbations of translational-rotational motion of unsteady axisymmetric three-bodies in the analogue of the Delaunaye-Andouye osculating elements have been obtained. The problem is investigated by methods of perturbation theory.

Development and characterisation of novel three-dimensional axisymmetric chiral auxetic structures

Novel three-dimensional (3D) axisymmetric chiral structures with negative and zero Poisson's ratios are presented based on the existing 3D conventional chiral unit cell. The conventional tetra-chiral unit cell is mapped to the axisymmetric space to form the new 3D axisymmetric chiral structure. Two different structure designs are characterised depending on the period delay of the sine curve representing the horizontal struts of the structure. The structures are fabricated using additive manufacturing technology and experimentally tested under compression loading conditions. The digital image correlation methodology is used to determine the Poisson's ratio dependence on the axial strain. The computational model of axisymmetric chiral structures is developed and validated using the experimental data. The computational model is then used to evaluate the new virtual axisymmetric chiral structures with graded cell structures. The newly developed axisymmetric structures show enhanced mechanical properties when compared to the existing 3D chiral structures.

A Monolithic 3D Printed Axisymmetric Co-Flow Single and Compound Emulsion Generator.

We report a microfluidic droplet generator which can produce single and compound droplets using a 3D axisymmetric co-flow structure. The design considered for the fabrication of the device integrated a user-friendly and cost-effective 3D printing process. To verify the performance of the device, single and compound emulsions of deionized water and mineral oil were generated and their features such as size, generation frequency, and emulsion structures were successfully characterized. In addition, the generation of bio emulsions such as alginate and collagen aqueous droplets in mineral oil was demonstrated in this study. Overall, the monolithic 3D printed axisymmetric droplet generator could offer any user an accessible and easy-to-utilize device for the generation of single and compound emulsions.

Free vibrations analysis of composite and hybrid axisymmetric shells

The free vibration of laminated composite (C) and hybrid axisymmetric shell structures, consisting of a composite laminated material sandwiched between two functionally graded material laminas (F1/C/F2), is analysed in the present work. The numerical solutions are obtained by expanding the variables in Fourier series in the circumferential direction and using conical frustum finite elements in the meridional direction. The implemented finite element is a simple conical frustum with two nodal circles, with ten degrees of freedom per nodal circle. This model requires only a reduced number of finite elements to model the geometry of axisymmetric structures, the integration procedures use one Gauss point, and the through the thickness properties variation in FGM laminas is modelled by a small number of virtual layers, resulting a very high computational efficiency. The in-house developed code presents very good solutions when compared with results obtained by alternative available models.

Effect of aspect ratio on coupled solute-thermocapillary convection instability in half-zone liquid bridge

Floating zone method is an important technology for growth of high integrity and high uniformity single crystal materials due to its free of crucible contamination. However, capillary convection in the melt is a great challenge to floating zone crystal growth. In this paper, numerical simulations are performed to investigate the coupled solute-thermocapillary convection in SixGe1-x system of the half-zone liquid bridge. The impact of aspect ratio, As, is also investigated on stability of capillary convection. For As = 0.5, the results show that pure solute capillary convection is very weak, which presents 2-D axisymmetric structure. The temperature field is mainly determined by thermal diffusion, while the concentration field is dominated by convection and solute diffusion together. Coupled solute-thermocapillary convection exhibits 3-D periodic and rotating oscillatory flow with the azimuthal wavenumber m = 4, while the pure thermocapillary convection presents a 3-D steady non-axisymmetric flow while solute capillary convection is absent. This means that instability of convection will increase when two kinds of capillary convection are coupled. When the height of the liquid bridge is changed from 5 mm to 10 mm with a constant radius of 10 mm, azimuthal wavenumber, m, of coupled capillary convection shows a strong dependence on aspect ratio. The relationship between the azimuthal wavenumber and aspect ratio can be written as m ? As = 2 or m ? As = 2.2. Further results indicated that when velocity of the monitoring point is large, corresponding concentration is also high at that moment, but the phases of concentration and velocity are not completely synchronized.

数値シミュレーションで得られた上陸前の台風Faxai (1915)の強度・構造変化

A numerical simulation of Typhoon Faxai (1915), which made landfall with a central pressure of 960 hPa in the Kanto region of Japan, was conducted using a nonhydrostatic numerical model with a 1-km grid spacing. Faxai sustained a symmetric structure until the landfall and caused severe damage due to strong winds. The simulation successfully simulated the realistic track and intensity of Faxai for 48 h around landfall. The simulated intensity was strong until the time of landfall, and the spatial size of the vortex was small. The structure of the simulated Faxai, identified as having an axisymmetric flow field and eyewall, was similar to that of a welldeveloped tropical cyclone (TC) in the tropics. Around the TC center, the surface latent heat flux was over 300 W m−2 until landfall, and the vertical wind shear was less than 9 m s−1 between the 1.5- and 12.0-km altitudes, which is relatively weak at midlatitudes. The maximum potential intensity (MPI) was calculated using environmental parameters around the simulated TC. The simulated and best track TC intensities exceeded the MPI for approximately 12 h before landfall, that is, the TC was in a superintense state. The superintensity was mainly caused by the presence of supergradient wind, which, in turn, resulted from the strong intensity and axisymmetric structure of the typhoon. The simulated TC satisfies the assumptions for the formulation of the MPI during the quasi-steady state, except for the gradient wind balance, implying that the structure of a TC is similar to that of a developed TC in the tropics. The present analyses suggest that the strong intensity of Faxai results from favorable environmental conditions and vortex structure.

Compact hybrid noise control system: ANC system equipped with circular noise barrier using theoretically calculated control filter

This paper proposes and investigates the feasibility of a compact noise control system for a wide frequency band, which can be easily installed and calibrated. Noise reduction over the workspace can be achieved by noise barriers, but becomes ineffective in low-frequency. Active noise control (ANC) is effective noise control method in low-frequency, so hybrid noise control systems combining a barrier and ANC were proposed. However, previous researches aimed at global noise control behind a large barrier for a stationary environment, which is very costly and difficult to reinstall. Despite its advantages in terms of space, cost, and mobility, a compact hybrid noise control system which is ANC system equipped with a compact size barrier for a specific space has been rarely studied due to the complex scattering effects and microphone arrangements in the control space. The present study aimed to investigate the feasibility of a compact hybrid noise control system using a theoretically calculated control filter, without microphones arrangement. Thus, can be various shapes of barrier and speaker arrangements, in this study, an axisymmetric structure is dealt with, since the theoretical equations had already been established and the computational amounts are reduced by simplifying it to two-dimensional problems. Theoretical noise reduction performance of a barrier, ANC, and the proposed noise control system are compared. Performance of ANC decreases with increasing frequency, and barrier is only effective in high-frequency bands. In contrast, the proposed noise control system achieved satisfactory noise reduction throughout the entire frequency range of interest. Following that, applying the theoretically calculated control filter was validated through experiments. The results showed that the proposed noise control system achieved a noise reduction of about 8 dB for a band-limited white noise in which the frequency range is 200–2000 Hz.

Polarization Study of Gamma-ray Binary Systems

Abstract The polarization of X-ray emission is a unique tool used to investigate the magnetic field structure around astrophysical objects. In this paper, we study the linear polarization of X-ray emissions from gamma-ray binary systems based on pulsar scenarios. We discuss synchrotron emission from pulsar wind particles accelerated by a standing shock. We explore three kinds of axisymmetric magnetic field structures: (i) toroidal magnetic fields, (ii) poloidal magnetic fields, and (iii) tangled magnetic fields. Because of the axisymmetric structure, the polarization angle of integrated emission is oriented along or perpendicular to the shock-cone axis projected on the sky and swings around 360° in one orbit. For the toroidal case, the polarization angle is always directed along the shock-cone axis and smoothly changes along the orbital phase. For the poloidal/tangled magnetic field, the direction of the polarization angle depends on the system parameters and orbital phase. In one orbit, the polarization degree for the toroidal case can reach the maximum value of the synchrotron radiation (∼70%), while the maximum polarization degree for poloidal/tangled field cases is several 10%. We apply our model to bright gamma-ray binary LS 5039 and make predictions for future observations. With the expected sensitivity of the Imaging X-ray Polarimetry Explorer, linear polarization can be detected by an observation of several days if the magnetic field is dominated by the toroidal magnetic field. If the magnetic field is dominated by the poloidal/tangled field, significant detection is expected with an observation longer than 10 days.

The Role of Random Vorticity Stretching in Tropical Depression Genesis

Abstract Tropical deep convection plays a key role in the tropical depression stage of tropical cyclogenesis by aggregating vorticity, but no existing theory can depict such a stochastic vorticity aggregation process. A vorticity probability distribution function (PDF) is proposed as a tool to predict the horizontal structure and wind speed of the tropical depression. The reason lies in the tendency for a vortex to adjust to an axisymmetric and monotonic vorticity structure. Assuming deep convection as independent and uniformly distributed vortex tube stretching events in the low–midtroposphere, repetitive vortex tube stretching will make the air column area shrink many times and significantly increase vorticity. A theory of the vorticity PDF is established by modeling the random stretching process as a Markov chain. The PDF turns out to be a weighted Poisson distribution, in good agreement with a randomly forced divergent barotropic model (weak temperature gradient model), and in rough agreement with a cloud-permitting simulation. The result shows that a stronger and sparser deep convective mode tends to produce more high-vorticity air columns, which leads to a more compact major vortex with a higher maximum wind. Based on the vorticity PDF theory, a parameterization of the eddy acceleration effect on the tangential flow is proposed.

The Internal Structure of Mercury's Core Inferred From Magnetic Observations

AbstractPrevious models of Mercury's core magnetic field based on high altitude data from first MESSENGER flybys revealed an axisymmetric structure of the field. Here, we use low altitude MESSENGER data covering the entire mission period to construct spherical harmonic models based on various spatial norms. Although we find a dominantly axisymmetric field, our models nevertheless include detectable deviations from axisymmetry. These non‐axisymmetric features appear at high latitudes, resembling intense geomagnetic flux patches at Earth's core‐mantle boundary. Based on this core field morphology, we then attempt to infer Mercury's internal structure. More specifically, assuming that Mercury's high‐latitude non‐axisymmetric features are concentrated by downwellings at the edge of the planet's inner core tangent cylinder, and accounting for the presence of a stably stratified layer at the top of Mercury's core, we establish a relation between the inner core size and the thickness of the stratified layer. Considering plausible ranges, we propose that Mercury's inner core size is about 500–660 km, which corresponds to a stratified layer thickness of 880–500 km, respectively.

Natural and Forced Vibrations of Axisymmetric Structure Taking into Account the Viscoelastic Properties of the Base

The paper considers an inhomogeneous elastic system; axisymmetric construction with foundation and foundation. Investigations of the interaction of the structure with the base. To study the interaction of the structure with the base, a cylindrical base model cut from half space is used in the calculations. It is believed that the lower part of the base is stationary, and the side surface is free. The eigenfrequencies and vibration modes of the considered heterogeneous system are determined. The influence of the geometric and physico-mechanical parameters of the base on the dynamic characteristics of the structure is investigated, the problem of the natural vibrations of the heterogeneous construction-base system is solved.

A novel squirrel cage eddy current coupling with adjustable radial air gap and its performance analysis

A novel squirrel cage eddy current coupling with adjustable radial air gap was presented, which can change the output speed by changing the air gap thickness in radial direction between the copper strips and the permanent magnet. It has the advantages of no axial force in speed regulation and less eccentric force in axisymmetric structure. The 2-D electromagnetic torque model of the rotor was established, and the influence of the air gap thickness on the electromagnetic torque was also studied by finite element method. Further, a novel method to solve the dynamic equation of the eddy current coupling was proposed based on the effect of air gap thickness and relative speed on torque characteristics, and was applied to the speed regulation performance analysis. In addition, the influence of the relative magnetic permeability of the permanent magnet back yoke and the internal rotor on the speed regulation performance was studied.

A Multiwavelength Dynamical State Analysis of ACT-CL J0019.6+0336

In our study, we show a multiwavelength view of ACT-CL J0019.6+0336 (which hosts a radio halo), to investigate the cluster dynamics, morphology, and ICM. We use a combination of XMM-Newton images, Dark Energy Survey (DES) imaging and photometry, SDSS spectroscopic information, and 1.16 GHz MeerKAT data to study the cluster properties. Various X-ray and optical morphology parameters are calculated to investigate the level of disturbance. We find disturbances in two X-ray parameters and the optical density map shows elongated and axisymmetric structures with the main cluster component southeast of the cluster centre and another component northwest of the cluster centre. We also find a BCG offset of ∼950 km/s from the mean velocity of the cluster, and a discrepancy between the SZ mass, X-ray mass, and dynamical mass (MX,500 and MSZ,500 lies >3σ away from Mdyn,500), showing that J0019 is a merging cluster and probably in a post-merging phase.

Supercollimation of Light Beams by Axisymmetric Aperiodic Photonic Structures

AbstractEfficient beam supercollimation is proposed and shown experimentally by axisymmetric aperiodic photonic structures. The structure consists of equidistant layers of concentric refraction index rings, with the transverse period of the rings varying from layer to layer along the structure. Numerically designed and optimized axisymmetric photonic structures are inscribed in silica glass by femtosecond pulses. Strong enhancement (more than by one order of magnitude) of the axial beam component is demonstrated, resulting in the record performance of the beam supercollimation.

Analysis of characteristic of acoustic radiation from axisymmetric pressure-resistant egg-shaped shells in the ocean environment

Due to the need for an ocean voyage, the shape and material of pressure-resistant structures of submersibles need to meet higher requirements. At present, the static mechanical properties of pressure-resistant systems have been extensively studied. However, it is still necessary to further explore its acoustic radiation noise to provide a reference for the overall acoustic design. A combination of the finite element method and wave superposition method (FEM-WSM) is used to calculate the acoustic radiation field of axisymmetric pressure-resistant structures in the ocean environment. Taking spherical, egg-shaped, and multi-body egg-shaped shells as examples, explores the distribution of acoustic radiation field of axisymmetric pressure-resistant shells under different shapes, materials, and submerging depths.

On the Regionality of Moist Kelvin Waves and the MJO: The Critical Role of the Background Zonal Flow

AbstractA global model with superparameterized physics is used to shed light on the observed regionality of convectively coupled Kelvin waves and the Madden‐Julian Oscillation (MJO). A series of aquaplanet simulations over zonally uniform sea‐surface temperatures is performed, in which the axisymmetric structure of the background zonal flow is altered through nudging, while maintaining a quasi‐fixed rainfall climatology. Results show that nudging at the equator to match profiles typical of the Indo‐Pacific or eastern Pacific sectors yields eastward‐moving tropical rain spectra typical of those sectors. Two different mechanistic pathways are identified as being responsible for this mean‐flow dependence, in addition to Doppler shifting effects. The first is through shifts of the Rossby wave critical line in the subtropical upper troposphere that affect the lateral forcing of Kelvin‐mode circulations at the equator by eastward and equatorward‐propagating eddies impinging on the tropics from higher latitudes. The second is through changes in the strength of the mean cyclonic shear in the lower tropical troposphere that affect the degree to which intraseasonal fluctuations in Kelvin‐mode zonal winds modulate the activity of higher‐frequency equatorial Rossby‐type eddies. In cases where the mean low‐level cyclonic shear is enhanced, the strength of this modulation, referred to as “shear‐induced eddy modulation” or SIEM, is also seen to be enhanced, such that MJO‐like modes of variability are rendered either unstable or near neutral, depending on the strength of the shear.