Cylinder Of Cross Section Research Articles

Torsion and Extension of Functionally Graded Mooney–Rivlin Cylinders

We analytically study finite torsional and extensional deformations of rubberlike material circular cylinders with the two material moduli in the Mooney–Rivlin relation assumed to be continuous functions of the undeformed radius. It is shown that under null resultant axial load on the end faces the cylinder length increases upon twisting. Furthermore, when the two moduli are affine functions of the radius the inhomogeneity parameters can be found to have the maximum shear stress occur at a pre-determined interior point. Whereas the radial stress is finite at the center of a cross-section of a homogeneous material cylinder, it may have large values for an inhomogeneous material cylinder. The closed-form solutions provided herein for the two moduli having affine, power-law and exponential functions of the radius should benefit numerical analysts verify their algorithms and engineers design soft material robots for improving their performance under torsional loads.

Effect of Nonlinear Magnetic Forces on Transverse Galloping Dynamics of Square Cylinders

Under the influence of cross-fluid flow, a cylinder of a square cross-section may gallop. Galloping is a self-excited vibration mode that can be utilized for low-power harvesting applications. The harvested power depends on several factors, including upstream flow velocity and system dynamics. This study explores the potential of magnetically-induced nonlinear stiffness to improve the power output of galloping-based energy harvesters. In this experimental study, the vibration response of a square rod with a mass ratio of 10 is investigated at a Reynolds number of 200. The vibration behavior of two identical coaxial square rods with magnetic monopoles at opposite ends is analyzed. Results reveal that the magnets’ configuration and strength significantly affect vibration amplitude and the critical flow velocity necessary for the onset of galloping.

Vortex-induced vibration of the variable cross-sectional cylinder cases in transverse direction at Re = 3900 using OpenFOAM

The one-degree-of-freedom (1-DOF) vortex-induced vibration in structures with varying cross-sectional shapes and incoming flows have been conducted using numerical simulation. The investigation centers on amplitude, frequency, spectrum, phase and fluid force coefficients. Additionally, the temporal and spatial characteristics as well as vortex dynamics mechanism are scrutinized, particularly during the cross-flow amplitude extremes. It can be indicated through studies that the cross-flow amplitudes in different incoming flows exhibit a distinctive distribution with three discernible branches. Frequency locking is found to amplify the dynamic response of the structure. Four tapered cylinder cases exhibit a delay in the location of the cross-flow amplitude extremes compared to two cylinder cases attributable to the influence of structural shear rate, which expands the upper branch. Superimposing incoming shear rate in the same direction as the structural shear rate not only enhances the cross-flow amplitude extremes but also broadens the range of forces and velocities distribution acting on the structure. Conversely, the imposition of incoming shear rate in the opposite direction to the structural shear rate leads to a contrary outcome. The incoming shear rate introduces secondary frequencies with higher energy in the spectrum characteristics of two cylinder cases, consequently promoting the amplification of the cross-flow amplitudes.

Tilt Angle Effect on Natural Convection Heat Transfer from an Inclined Array of Square Cylinders

Natural convection heat transfer from an inclined array of square cross-section cylinders is experimentally studied. Three cylinders of side length D = 0.02 m and 1 m length are used to form the inclined array. Three-cylinder axis inclination angles to the horizontal of 30°, 45°, and 60° are considered. The cylinders are heated using an internal heating element of constant heat flux. Surface temperatures are measured along the three surfaces of each cylinder; upper, lower, and the front side at nine points spaced evenly by 10 cm. The local circumference average temperature is obtained at each point. Four center-to-center distances to side length S/D = 1.25, 1.75, 2.25, and 2.75 are used. Local Nusselt numbers and the modified Rayleigh numbers are obtained for each cylinder at each circumference averaged temperature point. Results show that the lower cylinder heat transfer is least affected by the array compared to that of its single one followed by the middle and the upper cylinder for all S/D and the inclination angles used. The Nusselt number is degraded from that of the single cylinder at a small S/D and that degradation decreases as the S/D increases for all angles. It is observed that the Nusselt number enhances at the small cylinder axis tilt angle of 30°, followed by 45°, and 60°, especially at high modified Rayleigh numbers. New novel general empirical correlations for Nusselt numbers are obtained for each S/D using the cylinder axis tilt angle, the modified Rayleigh numbers, and the cylinder number in the array as parameters. A new general correlation is obtained for the array using the modified Rayleigh number, S/D, the cylinder axis tilt angle, and the cylinder sequential order number as parameters. These new correlations will help any engineering applications using such a configuration of the array.

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.

Frequency sweep study on the generation of dual-mode second harmonics (DMSH) on an isotropic nonlinear elastic cylindrical rod by T(0,1) mode

Nonlinear ultrasonic (NLU) guided wave (GW) measurements are more sensitive to microscale defects than linear measurements. This nonlinear phenomenon is helpful for early-stage damage detection in material for nondestructive evaluation (NDE) and structural health monitoring (SHM) applications. The amplitude of the higher harmonics generated in the material serves as the basis for the NLU measurement. Recent studies have reported the presence of dual-mode second harmonic (DMSH) on an isotropic nonlinear elastic plate and cylindrical structures. The fundamental non-dispersive mode shear horizontal SH0 and torsional T(0,1) modes can generate simultaneously propagating dual-mode second harmonic(DMSH) on plate and cylindrical guided media respectively. For the case of cylinders, at phase matching condition two dominant second harmonic fundamental longitudinal (l(0,1)) and orthogonal torsional (t(0,1)┴) mode are generated with significant amplitude. The particle vibration of the t(0,1)┴ mode was present in both orthogonal directions compared to conventional T(0,1) mode and hence called orthogonal torsional mode. The present work aims to study the behaviour of DMSH at different frequencies through a frequency sweep study on a weakly nonlinear elastic cylinder of circular cross-section via numerical simulations and validated experimentally for some selected cases. The wave propagation of the T(0,1) mode at several selected frequencies from 300 kHz to 2.2 MHz is chosen to explore the second harmonic mode for better understanding. At frequencies below 1.25 MHz, l(0,1) mode is faster than t(0,1)┴ mode; above 1.25 MHz, it was the other way around. The behaviour of harmonics was observed to be in accordance with the group and phase velocities at the corresponding frequencies in the dispersion curves. The evidence for the presence of DMSH was validated experimentally for some selected frequency cases at different propagation distances. The significance of DMSH is explored via numerical simulations and found that t(0,1)┴ mode is sensitive towards material degradation, while all other generated wave modes were not affected. Research shows that enough energy is available in the generated DMSH to be noticed experimentally and in numerical simulations. This improved understanding of the generation of DMSH across different frequencies would be helpful in new advanced NLU-based NDE and SHM applications.

An investigation of the cavitation and vibration phenomena in a cylindrical cyclone

Cylindrical cyclones are a popular choice for oil-water separation and sewage treatment in the petroleum industry. Here, we investigate the cavitation and vibration phenomena in a cylindrical cyclone with a vortex finder by using various cyclone operating parameters and conducting multiphase flow numerical simulations. The lowest point of pressure on the cross section of the main cylinder is defined as the pressure center point and is used to understand the generation of the flow field oscillation, which is shown to exhibit an approximately circular motion. This circular oscillation of the flow field is an important characteristic that influences the overall performance and behavior of the cyclone system. Cavitation analysis results show that an increase in the inlet velocity leads to more intense cavitation and an expansion of the cavitation area. At lower split ratios, cavitation primarily occurs at the junction of the inlet pipe and the main cylinder, while at higher split ratios, the cavitation area gradually extends into the overflow pipe. Additionally, structural response analysis demonstrates that increasing the inlet velocity and overflow split ratio significantly enhances the vibrational degree of the structure, leading to greater stress levels. Adjusting the oil content at the inlet has a relatively minimal impact on the structural response compared with the influence of the inlet velocity and split ratio. Furthermore, dimensional analysis is used to analyze the change of wall pressure, and the wall pressure that induces structural vibration can be calculated using the inlet velocity and the split ratio.

Estimation of the Needed Regolith for Covering Lunar Habitat by Protective Layer

Abstract The article deals with estimation of the amount of regolith to be mined with respect to the preparation of lunar habitat. Estimation of the size of the pit is related to the overlay of regolith for habitat made of a composite concrete-like structure. The evaluation is based on the number of inhabitants, necessary floor area, and the considered structure that is made of three segments. The first segment is a linear vault with a half cylinder cross section ending with a half sphere on both sides of the vault. Elementary formulas for the computation of volume of cylinder and sphere are applied.

Pressure gradient and an upstream cylinder on nanofluid flow around a heated cylinder: Heat transfer and entropy analysis

This study numerically investigates the nanofluid flow around a long heated cylinder of square cross-section (DSC) with height placed parallel to a cold wall at a fixed gap height The incident flow is Couette–Poiseuille (C–P) flow. Another cylinder of rectangular cross section (UREP) is placed on the upstream side in an inline arrangement with different gap spacings between the cylinders. The base fluid is chosen as the water and ethylene glycol–water mixture. Numerical experiments are made using staggered grid arrangement on non–uniform grid, finite volume methods, and Semi–Implicit Method for Pressure Linked Equations algorithm. Impact of pressure gradient at the inlet (due to C–P flow), position and shape (square/rectangular) of the UREP, nanoparticle concentration, and base fluid on the crowding of isotherms around edges of the DSC and hence to the heat transfer characteristics (Nusselt number and entropy generation rate density) is investigated. Bejan number is used to ratify that the irreversibility due to heat transfer is the major constituent of the total system irreversibility here. A reduction of heat transfer and entropy generation from the values of an isolated DSC is natural here due to the inline arrangement. An effort is made to improve the heat transfer by reducing the height of the UREP or/and by generating unsteadiness in the incoming flow to the DSC using a bluffer UREP or/and an increased pressure gradient. Finally, some scenarios are reported where the heat transfer decrement is less in comparison to that of the total system irreversibility.

Free vibration analysis of three-dimensional solids with arbitrary geometries using discrete Ritz method

A numerical method, discrete Ritz method (DRM), is proposed for the free vibration analysis of three-dimensional (3D) solids with arbitrary geometries. The problem is formulated within a cuboidal domain, and arbitrarily shaped 3D solid can be simulated by assigning cutouts within the cuboidal domain. Geometries of 3D solids are characterized by using level set functions. DRM transforms the problem into a variable stiffness system in which Chebyshev polynomials are used to approximate vibrational behavior and Gauss points are used to discretize the cuboidal domain. The vibration behaviors of arbitrarily shaped solids can be numerically simulated by setting the stiffness and thickness of Gauss points within the cutouts to zero. New formulations in DRM have resulted in completely standard energy functionals and computation procedures for arbitrarily shaped 3D solids. Free vibration behaviors of 3D solids, including polygonal cross-section cylinders, circular cylinders, rectangular plates with cutouts, perforated super-elliptical plates, ellipsoids, and pyramids, are investigated, and results are compared with those reported in the literature. DRM is shown to be capable of solving free vibration problems of complex-shaped 3D solids with high precision and stability.

Resonant triad interactions of gravity waves in cylindrical basins

We present the results of a theoretical investigation into the existence, evolution and excitation of resonant triads of nonlinear free-surface gravity waves confined to a cylinder of finite depth. It is well known that resonant triads are impossible for gravity waves in laterally unbounded domains; we demonstrate, however, that horizontal confinement of the fluid may induce resonant triads for particular fluid depths. For any three correlated wave modes arising in a cylinder of arbitrary cross-section, we prove necessary and sufficient conditions for the existence of a depth at which nonlinear resonance may arise, and show that the resultant critical depth is unique. We enumerate the low-frequency triads for circular cylinders, including a new class of resonances between standing and counter-propagating waves, and also briefly discuss annular and rectangular cylinders. Upon deriving the triad amplitude equations for a finite-depth cylinder of arbitrary cross-section, we deduce that the triad evolution is always periodic, and determine parameters controlling the efficiency of energy exchange. In order to excite a particular triad, we explore the influence of external forcing; in this case, the triad evolution may be periodic, quasi-periodic or chaotic. Finally, our results have potential implications on resonant water waves in man-made and natural basins, such as industrial-scale fluid tanks, harbours and bays.

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.

Effect of acoustic perturbation on the transition of vortex street in a flowing soap film

An experimental study of the effect of the acoustic perturbation on the evolution of wakes of cylinders with different cross sections and the same projected length (D) is conducted in a soap-film tunnel. Parameters for acoustic perturbation include different perturbation amplitude, frequency, and location. The formation of a secondary street structure is seen in the immediate downstream (∼21D–25D) of the triangular and rhomboid cylinder, while it is absent for the circular, square, and inverted triangular cylinder within the domain of the test section (∼135D). This study observed that the acoustic perturbation influences the location of the transition point at which the primary street transforms into the secondary street. For the triangular cylinder, the maximum shift in the location of the transition point in the downstream direction is 16.4%, and the maximum shift in the upstream direction is 16% when compared with the unperturbed flow. Similarly, for the rhomboid cylinder at two different acoustic perturbation conditions, the maximum shift in the downstream direction is 12.5%, and in the upstream direction, it is 25.4%, compared with the unperturbed flow. Further, the Strouhal number variation of the primary and secondary wake with perturbation frequency ratio is calculated for different perturbation cases. In both triangular and rhomboid cross-section cylinders, the Strouhal number of the secondary wake is almost 50% of that of the primary wake.

Design of Novel Multiband Radar Absorbers Using Cylindrical Frequency Selective Surfaces

Abstract In this paper, a novel ultra-thin and multi-band radar absorber structure using cylindrical frequency selective surfaces (FSS) is proposed. The unit cell of the structure consists of a curved square ring printed on a cylindrical dielectric spacer to realize strong resonance to achieve efficient absorption of the incident microwave energy. The use of novel cylindrical FSS coating results in a considerable decrease of the radar cross section of a perfect electric cylinder. Furthermore, our studies prove that the proposed absorbing structure can be easily scaled to desired frequencies, and extension to dual- and multiband performances is possible. Meanwhile, the operational principle of the proposed absorbers is briefly introduced.

Numerical Simulation for Cylindrical Electrostatic Precipitator: Effect of the Applied Voltage

Coaxial (wire-cylinder) electrodes arrangements are widely used for electrostatic deposition of dust particles in flue gases, when a high voltage is applied to electrodes immersed in air and provide a strongly non-uniform electric field. The efficiency of electrostatic filters mainly depends on the value of the applied voltage and the distribution of the electric field. In this work, a two-dimensional computer simulation was constructed to study the effect of different applied voltages (20, 22, 25, 26, 28, 30 kV) on the inner electrode and their effect on the efficiency of the electrostatic precipitator. Finite Element Method (FEM) and COMSOL Multiphysics software were used to simulate the cross section of a wire cylinder. The results showed that the velocity of the liquid and the charge accumulation of the particles increased with the increase of the applied voltage and also the efficiency of the precipitator increased and reached 100% with an applied voltage of 30 kV.

The Center of the Circle Fitting Optimization Algorithm Based on the Hough Transform for Crane

The basic principle of photogrammetry is mature and widely used in engineering. For gantry cranes, the base of which is usually a cylinder, the measurement of the center of the cylinder cross section is difficult, but its coordinates have an important impact on the safety evaluation of cranes. Aiming at the problem of measuring the center of a circle, an optimization method of fitting the center of a circle based on photogrammetry and the Hough transform is proposed. In this algorithm, the effect of image point distortion on the measurement accuracy is considered, and the similarity between ideal and actual midperpendicular is compared in the Hough space. The similarity is taken as the weight of the midperpendicular, and the space coordinates of the center of the circle are fitted again. This process needs to iterate repeatedly until convergence, and the fitting accuracy of the equal weighted midperpendicular fitting algorithm and the weighted midperpendicular fitting algorithm is compared. Finally, according to the characteristics of the algorithm, a theoretical verification experiment and an engineering experiment are carried out. The experimental results show that the proposed weighted midperpendicular fitting algorithm has a better effect than the equal weighted midperpendicular fitting algorithm, which obviously improves the fitting accuracy of the center of the circle and has high engineering value. In both experiments, the relative error was less than one percent. Especially in the engineering experiments, the weighted midperpendicular algorithm improved accuracy by an order of magnitude. Therefore, the proposed algorithm significantly improves the fitting accuracy of the center of the circle and effectively solves the difficulty that the center of the circle cannot be directly measured on the construction machinery.

Generalized lift force model under vortex shedding

This paper proposes a generalized model for vortex shedding around a static cylinder. This model is a first step to bridge the gap between two existing families of Vortex Induced Vibration (VIV) models , namely (1) stochastic spectral models and (2) wake-oscillator models with coupled fluid and structural equations. The first family is experimentally-based while the models of the second family typically rely on theoretical and phenomenological concepts. These models use a Van der Pol, Rayleigh or a combination of both oscillators for the lift equation. The proposed model generalizes these models by combining all third degree terms in the case of a static model, i.e. by considering the equation of the fluid oscillator only. It is possible to enrich existing models with a more complex parametric model because its parameters are identified from experimental data. A second specificity of the proposed model stems from the observation that, for a static cylinder in low turbulence flow, the envelope of the measured lift force is not perfectly mono-harmonic, nor deterministic. Turbulence in the wake is expected to create fluctuations in the lift envelope. In the proposed model, stochasticity is consequently introduced to reproduce these fluctuations. It is based as an additive exogenous noise as an input to the generalized shedding model, using a Von Karman spectrum. Its coefficients are adjusted so that the model reproduces the probability density function of the measured lift envelope (and its power spectral density). The methodology is applied to Wind Tunnel data of a static circular cylinder in subcritical and postcritical regimes. This set of data is used to identify the coefficients of non-linear terms and Von Karman spectrum. The lift fluctuation coefficient generated with the model matches results available in the literature for the considered regimes. This work focuses on a methodology to obtain a generalized vortex shedding model from experimental data measured on a static body. It can be applied to other cylinder cross-sections or even extended to cylinders arranged in tandem.

Semi-analytical models for deriving shock signals and response spectra on immersed and fluid-filled hulls subjected to shock waves

A semi-analytical model for a naval shock problem is proposed in this paper. It is applied to calculate the signals and response spectra which characterize the dynamic response of submarine hulls bearing equipment, when the latter is subjected to a pressure wave triggered by a far-field underwater explosion. It is also used to compare the configurations in which the hull may be filled or not with an inner fluid. The proposed model corresponds to a simplification of actual configurations, in the sense that the hull is simplified to a cross-section of a circular cylinder and that the equipment is simplified to a mass point. However, it allows to derive meaningful data – in particular the spectral response of the equipment and associated design shock response characteristics – which are representative of naval shock environment and useful for architects as design values in the early stages of naval projects. The details of the mathematical model are exposed, together with data validating them. The model proves useful to highlight the parameters of primary importance for the physics at stake and to investigate their influences on the acceleration and velocity levels of both the hull and the on-board equipment. Simple mathematical expressions are derived, and may prove useful for designers.

Dynamic Problem for a Viscoelastic Hollow Cylinder with Coaxial Elastic Inclusion


 
 
 A problem of non-stationary longitudinal wave propagation in the cross-section of an infinite hollow linear-viscoelastic cylinder with coaxial elastic inclusion is considered. On the contact surfaces between the layers, continuity of displacements and stresses is assumed. The solution of the problem is constructed using the integral Laplace transform in time with subsequent reversal. For the case when each of the relaxation kernels is a finite sum of exponentials, the original is presented as a series of residues. Thus, the process of constructing a non-stationary solution is reduced to the search for the roots of the characteristic transcendental equation. The derived solution allowed to investigate the transient wave propagation in a viscoelastic cylinder with coaxial elastic inclusion with specified initial data.
 
 

Scattering by Arbitrary Cross-Section Cylinders Based on the T-Matrix Approach and Cylindrical to Plane Waves Transformation

Multiple scattering of parallel cylinders with arbitrary cross section is computed using the T-matrix of each single scatterer and the general translational matrix for cylindrical waves. Usually, the recommended golden rule to compute the translational matrix is Graf’s addition theorem. However, this approach cannot be properly implemented for some geometries, such as in a two-cylinder case when the center of one of them falls within the minimum circular cylinder that circumscribes the other one. In order to overcome this limitation, a transformation between cylindrical waves and plane waves, followed by propagation of the latter, is proposed. The new approach succeeds due to an adequate truncation of the evanescent plane wave spectrum. This strategy is demonstrated by studying the scattering of three infinite elliptic metallic cylinders for different electrical sizes and observing the convergence of the results as a function of the truncated spectrum. Finally, to conclusively show the interest and applicability of the approach, two more complex problems are treated: a group of infinite elliptic metallic cylinders where two different sizes are combined and a practical real-life filter in substrate integrated waveguide (SIW) technology, including several groups of rectangular dielectric cylinders.