Cylindrical Research Articles

Systematical Theoretical Study of the Nonpoint Source Effects in Nuclear Medicine Shielding Calculation

Abstract The objective of this note was to systematically study the effects from nonpoint radiation sources on the nuclear medicine imaging room or uptake room shielding design. The dose from a nonpoint source to a location at a certain distance to the center of the source was calculated. A correction factor could be applied to the dose calculated using a point source model with the same distance to compensate the nonpoint source effects. The correction factor was a function only depending on the source relative dimension, the ratio of the source’s geometric dimension to the distance. Theoretical and numerical calculation were performed to calculate the correction factor on a one-dimensional line source, two-dimensional circular disc source, three-dimensional sphere, and cylinder sources. Our study indicated that for large nuclear medicine imaging rooms, the point source model was a good approximation for shielding design. For a small uptake room, a nonpoint source correction may be considered to calculate the barrier thickness.

Effect of groove sizes on the dynamic behavior of droplets impacting grooved cylindrical superhydrophobic surfaces

Effect of groove sizes on the dynamic behavior of droplets impacting grooved cylindrical superhydrophobic surfaces

A prediction model for in-line and cross-flow coupled vortex-induced vibration of a near-wall circular cylinder

A prediction model for in-line and cross-flow coupled vortex-induced vibration of a near-wall circular cylinder

Circular cylinders exposed to vortex-induced vibrations in restricted waters: VIV response from the bottom to the free surface

Circular cylinders exposed to vortex-induced vibrations in restricted waters: VIV response from the bottom to the free surface

Numerical investigating the impact of fluid properties and oscillation frequency on micro mixer efficiency.

In this research, the impact of differing densities and viscosities of two dissolving fluids on their mixing efficiency, as well as the effects of various excitation frequencies on the performance of the mixer, have been examined. For this purpose, a two-dimensional microchannel equipped with an oscillating circular cylinder was used, operating within a Strouhal number range of 0.1-0.55, with an oscillation amplitude of 0.4 cylinder diameters in a direction perpendicular to the flow direction, at a blockage ratio of and Reynolds and Schmidt numbers of 50 and 10, respectively, utilizing a finite volume method based on elements. The results obtained indicate that mixing two identical fluids represents an ideal condition, wherein the highest level of mixing occurs compared to mixing two fluids with differing densities and viscosities. As the difference in viscosity and density between the two fluids increases, the level of mixing decreases, such that an increase in the logarithmic viscosity ratio up to R=2 results in a 257.66% reduction in mixing, and an increase in the density ratio up to S=3 leads to a 170.08% reduction in mixing efficiency. However, at points where the density and viscosity increase factors are equal (s=eR), the increase in density has a greater impact on reducing the mixing efficiency compared to the increase in viscosity. Specifically, at an increase factor of 3 for both density and viscosity, density has a 50% greater effect on reducing mixing efficiency than viscosity. Furthermore, it is observed that when two fluids have different densities and viscosities, changes in the Strouhal number have a lesser impact on the mixing index compared to when the two fluids are identical. By creating a difference in viscosity and density between the two mixing fluids, the mixer exhibits unique and distinct performance, such that for each viscosity and density ratio, it is observed different optimal Strouhal numbers independently. This research provides a fundamental understanding of the effects of differing density and viscosity, as well as the impact of excitation frequency on the mixing efficiency of the two fluids.

Flow-induced vibrations of staggered circular cylinders

The flow-induced vibrations (FIVs) of staggered two-degree-of-freedom cylinders with a constant streamwise offset (L/D = 2, L is the streamwise spacing between the cylinders of diameter D) and varying cross-stream offset (0 ≤ S/D ≤ 5, S is the cross-stream spacing) were numerically simulated. The effects of S/D on the in-line and cross-flow vibrations, flow fields, distributions of the surface pressures, and the energy properties were comprehensively investigated to study the characteristics of the FIVs. The upstream cylinder primarily experiences vortex-induced vibrations (VIVs), while distinct FIVs of the downstream cylinder occur when S/D ranges from 0 to 3, and the flow characteristics vary with the reduced velocity (Vr) and S/D. When Vr = 3, vortex pairs along with reverse-flow reattachment are observed within the gap zone at small S/D. The pressures on the downstream cylinder become asymmetric due to the vortex strong interactions. When Vr = 7 and 11, a merging vortex emerges and moves closer to the rear surface of the downstream cylinder with increasing S/D, which increases negative pressure on the lower part of the downstream cylinder, further influencing the promoting effect of the merging vortex on structural vibrations. Moreover, when S/D ≥ 3, the effects of the upstream cylinder on the downstream cylinder diminish. Both cylinders exhibit identical vibrations and wake patterns, and the mean power distribution on the downstream cylinder becomes symmetrical with a magnitude similar to that of the upstream cylinder, which can be considered as two independent cylinders undergoing VIVs.

Flow and heat transfer characteristics of a porous-coated cylinder under simultaneous wave and current forces at a high Reynolds number

In the present study, a two-dimensional finite volume method is used to simulate the heat transfer rate of a circular cylinder coated with different structures of porous materials at Re=4800. The incompressible uniform flow is associated with deep-water waves created by a flap-type wave maker to investigate the effects of simultaneous current and wave forces on the pressure coefficients, flow characteristics, and heat transfer rate of cylinders wrapped by various porous structures (S2, S3, S4, and S5) and different Darcy numbers (Da=10, 10−1, and 10−2). According to the results, the porous layer thickness (e*) affects the outer shape of the porous coating and alters the influence of wave–current interaction on the flow characteristic. Therefore, compared to the current case, the lift and drag forces in the wave–current case increase in S2, but decrease in other porous structures. Moreover, S5, with the thickest porous coating showed the maximum heat transfer rate. Porous materials with low permeability decrease the impact of e* on heat transfer. However, the vortex-shedding patterns with thermal plumes become stronger with decreasing the Darcy number. The heat transfer rate of porous structures increases by about 42% as Da decreases from 10 to 0.1, and another 37% increase is observed at Da= 0.01, resulting in a total rise of 96% in the average Nusselt number (Nu¯). Therefore, the gap between the heat transfer rate of porous structures and the smooth cylinder (S1) increases by about 17%, 79%, and 126% at Da= 10, Da= 0.1, and Da= 0.01, respectively.

Coherent flow structures upstream a circular cylinder near a plane wall

Coherent flow structures upstream a circular cylinder near a plane wall

A numerical study of natural and mixed convection in an isothermally heated cylinder in a lid-driven cavity with extended surfaces filled with nano-fluid and encapsulation of nano-PCM

This research used Ansys Fluent to numerically examine the effects of incorporating horizontal fins into a circular cylinder heated isothermally. The cylinder is positioned at different places inside a square enclosure. Numerical analysis is conducted to investigate the heat transfer properties of steady, natural and mixed convection in an enclosure filled with pure water and MWCNT-water nanofluid. The work explores many situations, including cylinder position (1–9), nanoparticle concentration (1%−5%), Ri number and Ra numbers. The experiment revealed that the average Nusselt number varies greatly depending on the placement of the cylinder. It is highest when the cylinder is positioned near the surface of the cavity. Additionally, it was discovered that the Nusselt number increases as the concentration of nanoparticles increases, particularly for lower Richardson numbers and more significant Rayleigh numbers. Furthermore, it was noted that when the number of encapsulations increased, there was a substantial decrease in the Nusselt number.

Yang–Monti–Casale procedure for short bowel syndrome: preliminary geometric analysis

BACKGROUND: Currently autologic reconstructive surgery in the most significant approach in surgical therapy for enteral insufficiency due to short bowel syndrome. Possible application for short bowel surgery of widespread urologic Yang–Monti–Casale technique is an issue of interest. The technique includes cutting of small bowel segment antimesenteric border with a figured incision and second tubularization at an angle to the mesenterium fixation line which results in elongation and narrowing of the bowel segment. AIM: To determine geometric requirements of small bowel segment for Yang–Monti–Casale procedure to treat short bowel syndrome. MATERIALS AND METHODS: A mathematical model for resulting bowel segment after Yang–Monti–Casale procedure geometry dependency on original bowel length and width was observed. An object of the analysis was a cylindrical surface. Modeling assumptions were that the suface had no thickness and was unstretchable. Only surfaces with length more than width were taken into account. For establishing the dependency of bowel segment after procedure on original parameters a net of cutted with figured incise according the Yang–Monti–Casale technique cylindrical surface was considered. Bowel segment resulting width was computed as a half of the distance between the points that matched during the enteroplasty. Resulting length was computed as the ratio of the surface area and the resulting width. RESULTS: Yang–Monti–Casale procedure provides significant bowel segment elongation and narrowing if original bowel length to width ratio is not more than 2,5:1. The target bowel width 20 ± 2 mm is achieveable if original length is 60–80 mm and original width is 30–65 mm. CONCLUSIONS: Yang–Monti–Casale procedure may be considered as auxiliary technique for short bowel syndrome requiring bowel segment length 60–80 mm, width 30–65 mm, and length to width ratio not more than 2,5:1.

Insights using Hamilton-Crosser model in Williamson hybrid nanofluids with homogeneous-heterogeneous reactions and diagonal electromagnetic effects

The study of Carboxymethyl Cellulose (CMC)-based Williamson hybrid nanofluids offers a significant leap in fluid dynamics and thermal management systems. This research investigates the flow characteristics over a porous, horizontally stretched cylindrical surface, incorporating complex phenomena such as Hall current, ion slip, diagonal magnetic fields, suction, velocity slip and thermal slip. A unique aspect is the inclusion of uniform and exponentially space-dependent heat sources, critical for advanced thermal transport processes. Using the Hamilton-Crosser model for accurate thermophysical properties and the Runge-Kutta-Fehlberg method for numerical analysis, the study examines the impact of varying hybrid nanoparticle concentrations (4% to 20%) on flow behaviour. The findings reveal that nanoparticles enhance viscosity, significantly increasing skin friction and momentum transfer, even as factors like the Weissenberg number, Hall current and ion slip mitigate these effects. The study emphasises the thermal management advantages of Carboxymethyl Cellulose-based Williamson hybrid nanofluids, especially when heat sources and homogeneous-heterogeneous reactions are involved. Notable differences are observed between pure Carboxymethyl Cellulose-based Williamson fluids and their hybrid nanofluid counterparts, particularly in velocity, temperature distribution and reaction dynamics. These results are promising for practical applications such as magnetic drug targeting, porous heat exchangers, magnetohydrodynamic systems and electronic cooling. The research underscores the potential of Carboxymethyl Cellulose-based Williamson hybrid nanofluids to enhance energy efficiency and reliability in industrial processes, making them pivotal for future developments in heat management technologies.

New Torsional Surface Elastic Waves in Cylindrical Metamaterial Waveguides for Sensing Applications.

In this paper, we demonstrate that torsional surface elastic waves can propagate along the curved surface of a metamaterial elastic rod (cylinder) embedded in a conventional elastic medium. The crucial parameter of the metamaterial rod is its elastic compliance s44(1)ω, which varies as a function of frequency ω analogously to the dielectric function εω in Drude's model of metals. As a consequence, the elastic compliance s44(1)ω can take negative values s44(1)ω<0 as a function of frequency ω. Negative elastic compliance (s44(1)ω<0) enables the emergence of new surface states, i.e., new types of surface elastic waves. In fact, the proposed torsional elastic surface waves can be considered as an elastic analog of Surface Plasmon Polariton (SPP) electromagnetic (optical) waves propagating along a metallic rod (cylinder) embedded in a dielectric medium. Consequently, we developed the corresponding analytical equations, for the dispersion relation and group velocity of the new torsional elastic surface wave. The newly discovered torsional elastic surface waves exhibit virtually all extraordinary properties of their electromagnetic SPP counterparts, such as strong subwavelength concentration of the wave energy in the vicinity of the cylindrical surface (r=a) of the guiding rod, very low phase and group velocities, etc. Therefore, the new torsional elastic surface waves can be used in: (a) near-field subwavelength acoustic imaging (super-resolution), (b) acoustic wave trapping (zero group and phase velocity), etc. Importantly, the newly discovered torsional elastic surface waves can form a basis for the development of a new generation of ultrasonic sensors (e.g., viscosity sensors), biosensors, and chemosensors with a very high mass sensitivity.

Large-Eddy Simulation of the Flow Past a Circular Cylinder at Re = 130,000: Effects of Numerical Platforms and Single- and Double-Precision Arithmetic

Large-Eddy Simulation of the Flow Past a Circular Cylinder at Re = 130,000: Effects of Numerical Platforms and Single- and Double-Precision Arithmetic

ANALYTICAL DESCRIPTION OF THE POTENTIAL OF ELECTROSTATIC MULTIPOLE SYSTEMS BASED ON A CONDUCTING CIRCULAR CYLINDER

An urgent task of corpuscular optics and scientific instrumentation is the creation of new methods for calculating the physical and instrumental parameters of mass spectrometers. Leveraging the increased capabilities of computational technology, these methods provide a solid basis for the design and calculation of instruments with improved analytical capabilities. In this work, a method was developed for calculating the electrostatic field of multipole systems based on a conducting circular cylinder. This method uses the broad analytical capabilities of the theory of functions of a complex variable (TFCV). Analytical expressions are found for the electrostatic field potential of a quadrupole system for the case of infinitely narrow gaps between the electrodes. Analytical expressions for the derivatives of the potential are also obtained. A study was carried out of the influence of the finite size of the gaps between the electrodes on the field configuration. For this purpose, numerical simulations of planar electric fields satisfying the Laplace equation were carried out. The calculation of the electrostatic field potential was carried out using the boundary element method in two stages. First, the distribution of electric charge at the boundary was calculated according to the known boundary potential distribution, that is, the “inverse” problem was solved. Then, using the found values of the charge distribution and the found potential values, the “direct” problem was solved. To solve this problem, a method was developed for solving integral equations with singular and quasi-singular kernels, which provides high accuracy in field calculations for electron-optical systems (EOS) with rectilinear boundaries. The inaccuracies in the calculations resulted solely from rounding mistakes. In the case of an Equation of State (EOS) characterized by curved boundaries, the precision is dependent exclusively on how accurately the boundaries are represented using linear segments. For the purpose of segmenting the curved borders of the second-order EOS, these boundaries were broken down into arcs with an angular measurement not exceeding one degree.

HEAT TRANSFER IN THE CHANNELS OF THE HEAT EXCHANGER INTENDED FOR THE RECOVERY VENTILATION SYSTEM OF THE ROOM

Air exchange, or ventilation, systems are created to ensure comfortable conditions in rooms in terms of temperature, humidity, and oxygen content in the air. In energy-efficient buildings, the organization of such a system should include energy-saving measures. Among such measures, it should be noted the use of a recuperative heat exchanger, which provides partial heating of the cold outdoor air from the warm air removed from the room in the winter. This paper examines the characteristics of the heat exchanger - recuperator, which is a system of coaxial cylindrical surfaces made of copper. That is, this heat exchanger is a system of annular channels of the "tube-in-tube" type. Technical characteristics are defined for this heat exchanger, which include: thermal power, that is, the amount of heat transferred in the heat exchanger from one heat carrier to another per unit of time; consumption of heat carriers; the temperature of the air removed from the room into the environment after the recuperator; the temperature of the outside air entering the room after the recuperator. The dependence of these characteristics on the number and sizes of annular channels in the heat exchanger and on the pressure drop between the inlet and outlet cross-sections of the channels is investigated. It was determined that the dependence of the degrees of heating and cooling of air flows in the heat exchanger channels on the pressure differences between the inlet and outlet cross sections of the channels are different for heat exchangers with different number of channels and different widths.

Investigation of Effects of Feed Rate and Cutting-Edge Angle Variation on Surface Roughness in External Cylindrical Turning Process of Ms58 Brass Material

The Ms58 brass material was machined dry by the lathe’s external cylindrical surface turning method. Three different feeds (0.155, 0.088, and 0.028 mm/rev), 3 different cutting-edge angles (70°, 80°, and 90°), and three-spindle speeds (480, 630, and 1250 rpm) were used in machining experiments. The depth of the cut value was taken as a 0.5 mm constant. The effects of these different parameters on surface roughness values were investigated. For each surface roughness value measured from parts machined with other parameters, measurements were made five times, the largest and smallest values were discarded, and the average of the remaining 3 values was taken. This rigorous process of data collection ensured the reliability of the results. Graphs were prepared and examined with working parameters and surface roughness values. As a result, it was determined that the surface roughness value decreased with the decrease in feed and the increase in another parameter, the “cutting-edge angle” of the tool. When external cylindrical surface turning was performed with the experimental parameters of 480 rpm, a large cutting-edge angle of 90°, and a depth of cut of 0.5 mm within this study plan, the lowest average surface roughness was obtained as 1.228 µm.

Modal Analysis with Asymptotic Strips Boundary Conditions of Skewed Helical Gratings on Dielectric Pipes as Cylindrical Metasurfaces for Multi-Beam Holographic Rod Antennas.

A core dielectric cylindrical rod wrapped in a dielectric circular pipe whose outer surface is enclosed by a helical conducting strip grating that is skewed along the axial direction is herein analyzed using the asymptotic strip boundary conditions along with classical vector potential analysis. Targeted for use as a cylindrical holographic antenna, the resultant field solutions facilitate the aperture integration of the equivalent cylindrical surface currents to obtain the radiated far fields. As each rod section of a certain skew angle exhibits a distinct modal attribute; this topology allows for the distribution of the cylindrical surface impedance via the effective refractive index to be modulated, as in gradient-index (GRIN) materials. Beam steering can also be achieved by altering the skew angle via mechanical sliding motion while leaving the cylindrical structure itself unchanged, as opposed to impractically reconfiguring the geometrical and material parameters of the latter to attain each new beam direction. The results computed by the program code based on the proposed technique in terms of the modal dispersion and radiation patterns are compared with simulations by a software solver. Manufactured prototypes are measured, and experimentally acquired dispersion diagrams and radiation patterns are favorably compared with theoretical predictions.

Experimental investigation of the exit dynamics of a horizontal circular cylinder out of water and silicone oil

Experimental investigation of the exit dynamics of a horizontal circular cylinder out of water and silicone oil

Forming Control and Wear Behavior of M2 High-Speed Steel Produced by Direct Energy Deposition on Curved Surface.

Direct energy deposition (DED) technology shows promising applications in the production of roller die cutters. The optimization of process parameters, scanning strategies, and analyses of compressive properties and wear behavior are required prior to application. Therefore, this work investigated the influence of scanning strategy and overlap ratio on the microstructure, microhardness, compressive properties, and wear resistance of M2 high-speed steel (HSS) with DED on a 316 L cylindrical surface. The results reveal that along the deposition direction of the sample, the grain size gradually decreases, with hardness increasing from 187 HV in the matrix to 708 HV. As the overlap ratio increases, the grain size initially rises and then decreases, while hardness first declines and subsequently increases. The cross-scanning strategy effectively enhances the compressive strength by reducing porosity defects. Furthermore, the compressive strength of the samples initially increases with the overlap ratio before experiencing a slight decrease. The M-3 sample with a 50% overlap ratio exhibits the best compressive strength (3904 MPa). The wear rate decreases and then increases with the rising overlap ratio. Therefore, the M-3 sample, prepared using cross-scanning strategies with an overlap ratio of 50%, demonstrates a uniform and dense microstructure, resulting in superior wear resistance, and the wear rate is as low as 8 × 10-6 mm3·N-1·m-1. The current experimental results provide valuable references for the DED of die-cut knives.

Mapping the properties of wake-induced vibration on a circular cylinder

Mapping the properties of wake-induced vibration on a circular cylinder