Cylinders Of Different Diameters Research Articles

Cylindrical single-wall and double-wall structures with or without internal water subjected to underwater shock loading

A series of experimental studies were conducted for cylindrical structures subjected to underwater shock loading to understand their dynamic responses and failure characteristics. All tests were performed inside an anechoic water tank. The submerged test cylinders were freely suspended, and an underwater shock loading was generated by the Compressed Air Shock Pipe Underwater Release (CASPUR) system. Cylinders were made of two different materials. The first group of cylinders was fabricated from carbon fiber and resin using the filament winding technique. The winding angles were ± 45° resulting in the same properties along axial and hoop directions. The second group of cylinders was constructed using a 3-D printer with polylactic acid (PLA) material. The 3-D printed cylinders had an orthotropic material property with different values in the axial and hoop directions. Both single-wall and double-wall cylindrical structures were tested. The latter consisted of two concentric cylinders of different diameters with uniform spacing between them. In addition, within the single-wall cylinders and the annuli of double-wall cylinders, the water fill was varied at 0%, 50%, or 100%. Pressure and strain gages were used to measure the shock pressure and deformation of the cylinders. The number of cylinders such as single-wall or double-wall and the internal water resulted in significant effects on the measured dynamic response (i.e., strain gage response) as well as the failure loading and failure characteristics including major failure locations. Internal water reduced the strain on the cylinders and made them withstand greater shock loading for both single-wall and double-wall cylinders.

Dielectric cylinder discrimination with ANN using phase information of synthesized time-domain response

The application of the three-component stacked artificial neural network (ANN) for discrimination of dielectric cylinders of different diameters using phase information of synthesized time-domain response is considered. The network consists of two sparse autoencoders and the softmax unit. Neural networks are not tied to the frequency range, unlike many well-known methods based on the resonant properties of objects, and they are a powerful tool for object recognition. In contrast to well-known results, information about the phase of the time-domain signal, which is synthesized from multi-frequency data, is used for discrimination. For ANN training, phase images for cylinders with the radius of 15 to 35 mm are obtained using the method of auxiliary sources (MAS) The possibility of successful recognition was confirmed for the case of the diameter deviation of 1 mm and the presence of additive Gaussian noise with SNR of up to 0 dB.

Characterization of negative Poisson’s ratio of two/three dimensional auxetic knitted fabric with PET/PA/cotton from folded structures

Negative Poisson’s ratio tubular fabric plays an important role in mechanical and medical fields. To explore the impact of different raw materials and different structures on the negative Poisson’s ratio effect, flat knitting technology was used to characterize the negative Poisson’s ratio of three different structures of sheet and tubular fabrics made from polyester, cotton, and nylon. The tensile test and static burst test were applied to compare the performance of various sheet-knitted fabrics. The results show that yarn with better elasticity and elongation have a better auxetic effect. Fabrics with good auxetic effects have greater deflection and better energy absorption capacity. When measuring the longitudinal length variation of tubular knitted fabrics using cylinders of different diameters, it was found that when the number of weave cycles in a circle of tubular knitted fabrics is few, the negative Poisson’s ratio effect of tubular knitted fabrics is better than that of sheet knitted fabrics.

Darcy number influence on natural convection around porous cylinders in an enclosure using Darcy- Brinkman-Forchheimer model: LBM study

We evaluated numerically the combined impact of Darcy and Rayleigh number changes on natural convection around two vertically arranged hot porous cylinders of different diameters in a square enclosure. Numerical simulations are conducted by implementing lattice Boltzmann technique using the D2Q9 model. The Darcy-Brinkman-Forchheimer equations for porous medium are solved with a single-domain approach. The influence of Darcy number (10−6≤Da≤ 10−2) on rate of heat transfer from cylinders is described for 104≤Ra≤ 106 by altering the cylinder diameter from 0.1 to 0.4L. With increment of cylinder size, Ra and Da, heat transfer rates are found to improve. At Ra = 106, the highest enhancement occurs for D = 0.1L. On lower Rayleigh numbers (Ra = 104) as well as Darcy numbers (Da = 10−6), doubling the diameter of the cylinder increases heat transport by 41.5%. Consequently, when the diameter is multiplied by four, the improvement is 211%. At Ra = 106, the rate of augmentation from D = 0.2L–0.3L is lower than for the case when D = 0.1L and 0.2L. At D = 0.4L maximal transfer of heat arises when the cylinder is extremely permeable (i.e., Da = 10−2). This study has applications in the thermal management of a bank of electronic components.

Specimen size and shape effect on the compressive strength of concrete

The results of the investigation of the specimen size and shape effect on concrete strength indicators are presented in this paper. Research on the strength of concrete specimens in the form of cubes (150x150x150 mm) and cylinders of different diameters (50 mm, 100 mm and 150 mm) and heights (100 mm, 200 mm and 300 mm), under compression are carried out on Matest testing machine with Servo-Plus Evolution servo-drive control unit. Three specimens of each type are tested. Control specimens are made according to such ratios of materials that concrete corresponds to the strength class C16/20. All specimens are visually inspected for the presence of any defects, such as large pores, chips, or shrinkage cracks. After that, the actual measurements of all specimens are carried out. They showed minimal deviations from the planned size, which is considered acceptable. In order to check the reliability of the results, after the research of each type of specimen, calculations are carried out to determine the actual strength and the concrete grade. The actual dimensions of the faces and the results of the certain batch research are taken. The data obtained from the concrete specimens research on the test press are analyzed. Due to the formulas and data obtained after the investigation, the actual strength class of concrete for all specimens is determined. According to the results of the research, fracture graphs of all types of control specimens are constructed. The results show that the laboratory measurements are consistent with the literature results, namely that the compressive strength decreases with the specimen size increase. In the case of the smallest, non-standardized specimens (cylinders with 100 mm height and 50 mm diameter), the deviation of compressive strength tests is higher compared to other specimens. The graph is presented for visualizing the specimen type and size effect on concrete strength.

Numerical study of unsteady flow past compound cylinders

The flow over compound cylinders is simulated using computational fluid dynamic (CFD). Three contacting cylinders of different diameters, arranged in tandem with respect to the oncoming flow were examined at Reynolds number ReD = 333 based on the diameter of the middle cylinder, D. The proposed configuration simulates the wind flow over the satellite launch vehicles during the period of launch. Computations were performed for diameter-to-diameter ratio, d / D, of 0.8 and 0.6. The numerical results revealed the vortex formation and vortex shedding mechanism in the wake downstream of the cylinders. For d / D = 0.6, the near wake is wider than that of d / D = 0.8. It is also found that the base pressure coefficient values for d / D = 0.6 are lower than those for d / D = 0.8. These findings imply that the acting drag force on the cylinders for d / D = 0.6 is larger than that for d / D = 0.8. Concluding that, the base pressure coefficient depends on the diameter ratio d / D whereas, the computed vortex-shedding Strouhal number value was found to be 0.25 and is independent on the d / D ratio. Bangladesh J. Sci. Ind. Res. 57(4), 215-220, 2022

Experimental investigation of surface pressures, velocities, and dynamic structural analysis of tornadic winds on a luminary pole

Several engineering and media reports have demonstrated that luminary and lighting poles are susceptible to tornadic wind actions. This paper provides the first dynamic structural analysis of a 1:50 geometrically scaled model of a generic luminary pole of a circular cross-section tested under transient wind loads caused by translating tornado-like vortices (TLVs). The physical experiments were performed in the WindEEE Dome tornado simulator at Western University (Canada). The tornadic wind actions on the pole are also compared against the reference atmospheric boundary layer (ABL) wind gust with the mean recurrent period of 50 years. Three different positions of the luminary pole in respect to the TLV path were considered: (1) TLV center passing over the pole; (2) TLV core radius passing over the pole; and (3) an intermediate case in which the pole was positioned between the TLV center and the core radius. In all cases two circular cylinders of different diameters were used to simulate two different cross-sections of an actual luminary pole. Our study demonstrates that luminary poles are more susceptible to tornadic wind actions compared to ABL winds. The tip displacements of the pole were larger in the TLVs and the direction and magnitude of the displacements were dependent on the relative positions of the TLVs and the luminary pole. The highest wind forces were observed in the regions characterized by strong tangential wind speeds. The entire luminary pole was subjected to negative pressure coefficients during the TLV passage. However, our structural analysis showed that the pole always stayed in the elastic region of deformation and there was no permanent bending or collapse of the structure.

Opposed-flow flame spread over cylindrical fuels: Spread rate formulas and experimental verification

Opposed-Flow flame spread over flat condensed fuel has been studied for many decades as it constitutes a fundamental problem of fire studies. Although cylindrical fuels offer the simplicity of axial symmetry, despite many previous attempts, there are no easy-to-use flame spread rate expressions that connect spread rate in this geometry to the exact solution for flame spread rate for flat fuels. Also no criterion exists to delineate a thermally thin cylindrical fuel from a thermally thick one. In this work, we use the scaling approach to develop closed-form expressions for flame spread rate for opposed-flow flame spread over thermally thin and thick cylindrical fuels. The approach is validated by reproducing the theoretical expressions of de Ris for flat fuels. By equating the heated layer thickness with the radius, a criterion is developed for delineating thermally thin cylinders from thermally thick ones. It is shown that the spread rate is always higher for a cylindrical fuel when compared to a flat fuel with a half-thickness equal to the radius of the cylindrical sample. The cylindrical spread rate depends on the same factors as that of flat fuels with an additional coefficient arising out of heat transfer enhanced by the curvature effect. For thermally thin cylinders, the spread rate is predicted to be at least two times faster than the corresponding flat fuel. For thermally thick fuels also the spread rate is significantly higher, but as the radius is increased the flat fuel limit is approached. Spread rates obtained from experiments performed with PMMA cylinders of different diameters in downward configuration are shown to agree well with the theoretical expressions. The thermally thick limit for downward spread, interestingly, is achieved for PMMA cylinders as narrow as 2.4 mm diameter.

ESTUDIO DE LA INESTABILIDAD DE VON KÁRMÁN ORIGINADA POR UN SISTEMA DE CILINDROS BINARIOS

Experimental results are presented of the temporal evolution of the wake associated with von Kármán, instability produced by a system of two vertical cylinders of different diameters (binary cylindrical system) facing a uniform airflow. The goal is to study the influence of the binary system on the linear stability of the wake at moderate Reynolds numbers, as well as the vortex emission. From the measurements of the velocity profiles we were able to analyze the wake’s dynamic behaviour in both the subcritical and critical ranges. Furthermore, it was possible to determine the frequency content of the vortex emission of the system, finding a coupling (lock-in) in the wake of both cylinders at the onset of the von Kármán instability. This coupling is developed, even, in the condition of greatest distance between the wakes(α=90◦). The non-linear condition of the wake is reflected in the power spectrum (PSD) of the velocity time series, presenting additional frequency modes to the fundamental vortex shedding frequency of each cylinder.

Dual-energy X-ray absorptiometry (DXA) to measure bone mineral density (BMD) for diagnosis of osteoporosis - experimental data from artificial vertebrae confirms significant dependence on bone size

IntroductionThe WHO definition of osteoporosis, and published BMD (Bone Mineral Density) references ranges, do not consider differences in bone size. Because it is a two-dimensional technique, and cannot measure bone depth, aBMD (areal BMD) measured using DXA (Dual-energy X-Ray Absorptiometry) is affected by bone size variability. Mathematical models have been devised to correct aBMD for bone size, but these are confounded by variations in soft tissue surrounding bone. Confirmation of the actual quantitative effect on clinical results for patients requires precise changes in bone size and mineral density, but studies of humans and animals are limited by the inability to precisely control these in natural bones. PurposeThe objectives of this experiment were to obtain precise, repeatable, quantitative data from sets of artificial vertebrae to confirm the dependence of aBMD on bone size in clinical practice, and to test the effect of applying corrections based on assumptions that the vertebrae were simple geometric shapes to produce corrected BMAD (Bone Mineral Apparent Density). Methods and materialsFour sets of artificial bones, each set containing four cylinders of different diameters but identical in height, were constructed by casting a mixture of epoxy resin and calcium carbonate powder into a mould. The cylinders were considered to be artificial vertebrae L1 to L4 so that all four in a set may be tested in a single scan. The X-Ray attenuation of the material used was varied between the sets, to represent differences in BMD. Each set of vertebrae was inserted into a soft-tissue analogue and DXA scanned, in the anteroposterior position, with the GE Lunar Prodigy and the Hologic Discovery. ResultsThe results verify the theoretical direct proportionality between aBMD and diameter, confirming that aBMD is significantly affected by bone size. Applying a BMAD correction, by assuming the vertebrae to be cylinders, reduced the effect of change in bone diameter by approximately two orders of magnitude to an insignificant level. ConclusionThis experiment has confirmed that BMD measured using DXA, accepted in clinical practice as the “gold standard” means of diagnosing osteoporosis, could lead to misdiagnosis because it is significantly affected by differences in bone size.

Flow-induced vibration on two tandem cylinders of different diameters and spacing ratios

This work numerically investigates flow-induced vibration (FIV) of two tandem cylinders of unequal diameters at a Reynolds number of 100 and at a range of reduced velocity 2 − 10. Particular attention is paid to assimilating the effects of the cylinder diameter ratio (0.2 − 1) and the cylinder spacing ratio 1.5, 3.5 and 5.5 on vibration responses, frequency responses, lock-in, and wake structure. The cylinder-to-fluid mass ratio is considered as one, and the damping coefficient is set to zero to attain maximum oscillation amplitude. The obtained results reveal that FIV is highly sensitive to both diameter and spacing ratios, and the wake interference involved is intricate. With a decrease in diameter ratio, the upstream cylinder oscillation is affected due to a change in its effective Reynolds number while its wake induces a significant effect on the downstream cylinder. The lowest diameter ratio of 0.2 exhibits a de-energized wake suppressing the oscillation of the downstream cylinder. At a moderate diameter ratio of 0.6, suppressed and excited oscillations of the downstream cylinder are observed at spacing ratios 1.5 and 3.5, respectively.

Effect of Gap and Diameter Ratio on Vortex-induced Forces for Cylinders in Tandem at Re=100

Abstract The article investigates fluctuations of the vortex-induced loads related to the effects of gap and diameter ratio on the mean drag and lift coefficients of the downstream cylinder, when two circular stationary cylinders of different diameters are arranged in a tandem configuration. The study is performed with the method of computational fluid dynamics for the low Reynolds number of 100. The benchmarking of the numerical model is followed by the parametric investigation with the variation of: a) the ratio of diameters of the upstream to downstream cylinder (d/D), in order to observe the effects associated with relative sizes of structures; b) the gap-to-diameter ratio (G/D), in order to observe the combined effects of varying these geometrical quantities. The results demonstrate a rapid change in the mean drag and lift coefficient values at the gap-to-diameter ratio between 2.0 and 3.0 at the diameter ratios of 0.7 and 1.0.

Design and Test of an Integrated Measurement System for Multi-Hole Probe Calibration and Vortex Measurement.

Multi-hole probes can simultaneously measure the velocity and direction of a flow field, obtain the distribution of the flow field in a three-dimensional space, and obtain the vortex information in the flow field. Moreover, a multi-hole probe needs to be calibrated while in use; therefore, a three-coordinate, multi-directional rotatable testing system, which can measure the flow field at any position and at any angle, was designed herein. A hemispherical seven-hole probe was calibrated with this test system, and the flow field around cylinders of different diameters was measured to obtain the pressure distribution and vortex shedding frequency. Furthermore, the designed test system’s ability to perform a multi-angle and multi-azimuth testing during the calibration of a multi-hole probe was verified. Simultaneously, through data mining of the multi-hole probe, vortices were measured, and periodic vortices were detected.

Experimental investigation of downstream cylinder vibrations caused by FIV in the presence of upstream stationary cylinder

The mechanism of flow induced vibrations (FIV) exists in many engineering applications and plays a significant role. In offshore engineering, the risers subjected to flow induced vibrations. In this study, two circular cylinders of different diameters are arranged in tandem manner. In cross-flow transverse direction, the upstream cylinder is fixed, while the downstream cylinder is subjected to vibrations. This study carries out experiments in wind tunnel, which focuses on significant vibration-galloping. Variable mass-damping ratio is used to achieve the critical velocity corresponding to onset galloping vibration. In the present study, the diameter ratio is 0.4 and the gap L is 1.5D, and 3.5D. In the wind tunnel experiments, by changing the mass of the vibrating cylinder, the corresponding values of damping ratio, results in variable mass damping ratio m*ζ. For each value of m*ζ, the amplitude, frequency at every reduced velocity will be obtained at first, the critical velocity and stability map will be summarized. At static area between lock-in and galloping (desynchronization branch), a uniform initial displacement was set to get the total damping ratio. This study also investigates the relationship among the total damping ratio, m*ζ and critical velocity.

Experiments and Simulations of Free-Surface Flow behind a Finite Height Rigid Vertical Cylinder

We present the results of a combined experimental and numerical study of the free-surface flow behind a finite height rigid vertical cylinder. The experiments measure the drag and the wake angle on cylinders of different diameters for a range of velocities corresponding to 30,000 <Re< 200,000 and 0.2<Fr<2 where the Reynolds and Froude numbers are based on the diameter. The three-dimensional large eddy simulations use a conservative level-set method for the air-water interface, thus predicting the pressure, the vorticity, the free-surface elevation and the onset of air entrainment. The deep flow looks like single phase turbulent flow past a cylinder, but close to the free-surface, the interaction between the wall, the free-surface and the flow is taking place, leading to a reduced cylinder drag and the appearance of V-shaped surface wave patterns. For large velocities, vortex shedding is suppressed in a layer region behind the cylinder below the free surface. The wave patterns mostly follow the capillary-gravity theory, which predicts the crest lines cusps. Interestingly, it also indicates the regions of strong elevation fluctuations and the location of air entrainment observed in the experiments. Overall, these new simulation results, drag, wake angle and onset of air entrainment, compare quantitatively with experiments.

Vortex induced vibrations of short side by side cylinders

Staggered cylinders of different diameters is a common configuration in offshore design, including e.g. clamped risers, piggy-back solutions and piping systems. Current design practice is not clearly formulated in relevant design codes such as DNVGL-RP-F105 and DNVGL-RP-C205. Conservatively, it is often assumed that flow acceleration due to a neighboring cylinder causes up to a doubling of the incoming flow velocity depending on incidence angle and difference in cylinder diameter. Doubling the incoming particle velocity compared to free stream would decrease the required support distance by around 30%. Particularly in conditions with significant diameter disparity, flow acceleration effects due to the larger cylinder of the two can thus cause strict requirements to support distances on the smaller. Designers may want to reduce the number of support points due to cost, maintenance requirements and rigid structure availability, particularly in piping system arrangements. Recent research on piggy-back pipeline vortex induced vibrations have complemented traditional understanding of such configurations, allowing for improved design guidelines. In the present study, a detailed meta study of available laboratory and numerical work is performed, and the resulting findings are translated into simple design guidelines for piggy-back and other staggered arrangements. The present paper provides clear recommendations for improvements to the relevant recommended practices.

Higher-Order Turbulence Around Different Circular Cylinders Using Particle Image Velocimetry

Abstract Wakes and higher-order turbulence around circular cylinders of different diameters are investigated using particle image velocimetry measurements. The cylinder Reynolds number (Red) is defined by the depth-averaged velocity, cylinder diameter, and kinematic viscosity. The influence of Red on third-order moment of velocity fluctuations, turbulent kinetic energy (TKE) flux, TKE budget, and turbulent length scales are presented. The intermittency factor (IF) and quadrant analysis around the cylinders are discussed for Red values ranging from 12,600 to 21,000. The energy budget mostly near free surface upstream and near-bed downstream is changed due to Red. Stream-wise and transverse TKE fluxes decreased significantly with Red, but not the vertical flux. Stream-wise skewness changed sign from positive to negative at a certain critical distance downstream, while vertical skewness showed reversed effect with Red. Negative stream-wise skewness and positive vertical skewness indicate the occurrence of ejection events. On the downstream, the production and dissipation rates increased with Red, whereas an opposite trend was observed for dissipation only on the upstream. Increase of Red led to an increase in the Kolmogorov length-scale much higher on the upstream than the downstream, whereas it showed depleting effect on Taylor's length-scale on the upstream and an increasing effect on the downstream. Ejection and sweep events were more prominent in the downstream near the cylinder than upstream with higher values of shear stress on the downstream. The sum of the shear stress contributions of all quadrant events increased consistently with an increase in Red near the cylinder.

Nondimensionalized semi-empirical equation to predict secondary load cycles on vertical cylinders of different diameters

Theoretical solutions including the Morison equation have been widely used to estimate the wave forces exerted on offshore structures of vertical cylindrical configuration. However, none of those methods can accurately predict the wave force of the secondary load cycle induced by a steep wave acting on the cylinder. In this study, regular waves of different wave steepness are generated using an experimental wave flume with a piston-type wavemaker, and the forces exerted on the cylinders of three different diameters are investigated. Using the data-fitting method, the difference between the experimentally measured wave force and that calculated by the Morison equation is empirically formulated, and the effects of key non-dimensional parameters on the force difference function are analyzed. The results show that the amplitude and phase of the force difference function are mainly governed by the incident wave condition including the relative depth, relative amplitude, and relative elevation. On the other hand, the effect of the relative radius is negligible when the diameter-to-wavelength ratio satisfies the small-scale structure condition. The proposed equation is valid for predicting the non-breaking regular wave forces exerted on a vertical cylinder when the secondary load cycle occurs and can be utilized in wave-structure interaction problems.

Theory and practice of asymmetrical longitudinal rolling

"In the national and international literature of the rolling theory, it is usually resented the plastic distortion between cylinders with equal diameter, meaning the symmetrical rolling, although this process represents only an abstract opposed to the normal conditions, because there exists a difference between the working diameters of the cylinders, and sometimes right after construction the rolling mill is equipped with cylinders of different diameters. It is worth mentioning that for a series of aspects like: the distribution of the unitary pressure on the contact surfaces, the reduction between the cylinders, the bending of the bar exiting from among the cylinders and many others, there are contradictory opinions which are explained through the difficulties that the experimental study of these phenomena imposes, but also because of the different factors which influence or modify the volumetric pressure scheme of the metal material at rolling. For the research of these difficult phenomena the author of the paper conceives an original appliance which allows experiments in order to reach conclusions for the rolling theory among equal diameter cylinders, but also for the industrial practice."

Balancing act between quantitative and qualitative image quality between nonionic iodinated dimer and monomer at various vessel sizes during computed tomography: a phantom study

Purpose: Investigate the impact of nonionic dimer and monomer on iodine quantification in different vessel sizes when employing a vascular specific phantom and varying iodinated contrast media (ICM) concentrations during computed tomography (CT). Materials and Methods: We created a vascular specific phantom (30 cm) to simulate human blood vessel diameters (25 cylinders of different diameters: 10 × 9mm, 10 × 12mm and 5 × 21mm). The phantom was filled with two ICM separately: Group: Iohexol(monomer)350 mg ml−1 and B: Iodixanol(Dimer)320 mg ml−1. Cylinders of same size were filled with increasing ICM concentration(10%–100%) while large cylinders were filled in quartiles(25%–100%). Phantom was scanned with different tube potential (80–140kVp), current (50–400mAs), reconstruction method [filtered back projection (FBP), hybrid-based iterative reconstruction (HBIR) and model-based iterative reconstruction (MBIR)] for each ICM. Chi-square was employed to compare mean opacification, contrast/noise ratio (CNR) and noise. Qualitative analysis was assessed by Visual grading characteristic (VGC) and Cohens-kappa analyses. Results: At 80 and140kVp significant difference in opacification between Group A (2054 ± 1040HU and 1696 ± 1027HU) and B (2169 ± 1105HU and 1568 ± 1034HU) was demonstrated (p < 0.001). However, at 100 and 120kVp no difference was noted (p > 0.05). When comparing image noise, it was higher in Group A compared to B (p < 0.05). CNR was higher in Group B (119.99 ± 126.10HU) than A (107.09 ± 102.56HU) (p < 0.0001). VGC: Group A outperformed B in image opacification in all vessel sizes and ICM concentrations except at medium vessels with concentration group 2(0.4–0.6 mg ml−1). Cohens’-kappa: agreement in opacification between each ICM group and iodine concentration 1(0–0.3 mg ml−1): κ = 0.253 and 0.014 respectively, concentration 2(0.4–0.6 mg ml−1):κ = −0.017 and −0.005 respectively and concentration 3(0.7–1 mg ml−1):κ = 0.031 and 0.115 respectively. Conclusion: Nonionic dimer (Iodixanol) surpasses monomer (Iohexol) in quantitative image quality assessment by having lower image noise and higher CNR during CT.